FEASIBILITY STUDY REPORT · This Feasibility Study (FS) Report has been prepared by Goldberg Zoino Associates of New York, P.C. “Supplemental Remedial Investigative Report” (October

FEASIBILITY STUDY REPORT

FORMER NUHART PLASTIC MANUFACTURING SITE

January 19, 2017 PREPARED FOR: DUPONT STREET DEVELOPERS, LLC 87-10 Queens Blvd Elmhurst, NY 11373

PREPARED BY: Goldberg Zoino & Associates of New York, P.C. d/b/a GZA GeoEnvironmental of New York 104 West 29th Street, 10th Floor New York, New York 10001

Copyright© 2017 GZA GeoEnvironmental of New York.

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TABLE OF CONTENTS

1.0 INTRODUCTION AND BACKGROUND INFORMATION ..................................................................1-1

1.1 SITE LOCATION AND DESCRIPTION ....................................................................................... 1-1

1.2 SITE ENVIRONMENTAL SETTING ........................................................................................... 1-3

1.3 SITE HISTORY .......................................................................................................................... 1-3

2.0 SUMMARY OF NATURE AND EXTENT OF CONTAMINATION AND POTENTIAL EXPOSURES, ADDITIONAL INVESTIGATIONS...................................................................................................2-1

2.1 NATURE AND EXTENT OF CONTAMINATION AND POTENTIAL EXPOSURES ....................... 2-1

2.1.1 Soil .......................................................................................................................................... 2-1

2.1.2 Groundwater .......................................................................................................................... 2-3

2.1.3 Soil Vapor, Sub-Slab Soil Vapor and Indoor/Outdoor Air ....................................................... 2-4

2.2 ADDITIONAL INVESTIGATIONS .............................................................................................. 2-5

2.2.1 LNAPL Testing — Assessment of Well Conditions, Migration Rate, Viscosity ........................ 2-6

2.2.2 LNAPL Depth and Thickness ................................................................................................... 2-9

2.2.3 Underground Utility Survey .................................................................................................. 2-11

2.2.4 Groundwater Flow Direction ................................................................................................ 2-14

2.2.5 Stratigraphic Cross-Sections ................................................................................................. 2-18

2.2.6 Waste Evaluations .............................................................................................................. 2-27

2.2.7 RCRA Closure ........................................................................................................................ 2-29

3.0 REMEDIAL GOALS, REMEDIAL ACTION OBJECTIVES, GENERAL RESPONSE ACTIONS, REMEDIAL TECHNOLOGY SCREENING .........................................................................................................3-1

3.1 REMEDIAL GOALS .................................................................................................................. 3-1

3.2 REMEDIAL ACTION OBJECTIVES ............................................................................................ 3-2

3.3 IDENTIFICATION OF GENERAL RESPONSE ACTIONS ............................................................. 3-4

3.4 IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES ..................................... 3-6

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4.0 REMEDIAL ACTION ALTERNATIVES .............................................................................................4-1

4.1 EVALUATION OF REMEDIAL ACTION ALTERNATIVES ........................................................... 4-1

4.1.1 Alternative 1 - No Action Alternative ..................................................................................... 4-2

4.1.2 Alternative 2 - Air Sparging/Soil Vapor Extraction, Off-site Physical Barrier, LNAPL Extraction/Disposal, Groundwater/ LNAPL Monitoring, Soil Vapor/SVI Monitoring, Limited On-site Removals, and ECs/ICs ............................................................................................... 4-2

4.1.3 Alternative 3: Physical Barrier with LNAPL Extraction/Disposal, Option for On-site In-situ Stabilization of LNAPL, Targeted Soil Excavation and Disposal with In-Situ Chemical Treatment, Air Sparging/Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization and Vapor Barrier Soil Vapor/SVI Monitoring, and ECs/ICs ........ 4-27

4.1.4 Alternative 4: Soil and LNAPL Excavation and Disposal, LNAPL Physical Barriers and Extraction/Disposal, Groundwater Air Sparging /Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization, Soil Vapor/SVI Monitoring, and ECs/ICs .......................................................................................................................... 4-57

4.1.5 Alternative 5: Groundwater Cutoff Walls with LNAPL Extraction/Disposal, Targeted Excavation, In-Situ Thermal Treatment Followed with In-Situ Chemical Oxidation, Off-Site Physical Barrier, Air Sparging/Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization and Vapor Barrier, Soil Vapor/SVI Monitoring, and ECs/ICs. ........... 4-87

4.2 RECOMMENDED REMEDIAL ALTERNATIVE ...................................................................... 4-122

4.2.1 Alternative Evaluation ........................................................................................................ 4-122

4.2.2. Recommended Remedial Alternative .............................................................................. 4-125

5.0 REFERENCES .............................................................................................................................5-1

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LIST OF TABLES

Table No. Description Page No

TABLE 2.2.6.1 PRODUCT PCB ANALYTICAL DATA………………………………………………………………………………….…2-30

TABLE 3.4.1 SCREENING OF SOIL REMEDIAL TECHNOLOGIES………………………………………………………………..……3-9

TABLE 3.4.2 SCREENING OF GROUNDWATER REMEDIAL TECHNOLOGIES……………………………………………3-11

TABLE 3.4.3 SCREENING OF SOIL VAPOR REMEDIAL TECHNOLOGIES………………………………………………...…3-12

TABLE 3.4.4 SCREENING OF LNAPL REMEDIAL TECHNOLOGIES ………………………………………………………...…3-13

TABLE 4.1.2.1 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 AS/SVE ……………………………………………….4-4

TABLE 4.1.2.2 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 OFF-SITE LNAPL PHYSICAL BARRIER…..4-8

TABLE4.1.2.3 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 LNAPL EXTRACTION/DISPOSAL ……...…4-11

TABLE 4.1.2.4 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 GROUNDWATER/LNAPL MONITORING………………………………………………………………………………………………………………….4-13

TABLE 4.1.2.5 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 SOIL VAPOR/SVI MONITORING ……………………………………………………………………………………………………………………………………..…4-16

TABLE 4.1.2.6 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 LIMITED ON-SITE REMOVALS………………………………………………………………………………………………………………………4-19

TABLE 4.1.2.7 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 IMPLEMENT ECS AND ICS………………….4-21

TABLE 4.1.2.8 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2……………………………………………………….….4-26

TABLE 4.1.3.1 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 LNAPL PHYSICAL BARRIER AND EXTRACTION/DISPOSAL……………………………………………………………………………………………….….4-30

TABLE 4.1.3.1A ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 IN SITU SOLIDIFICATION /STABILIZATION, LNAPL PHYSICAL BARRIER AND EXTRACTION/DISPOSAL……………………………………………….….4-34

TABLE 4.1.3.2 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 TARGETED SOIL EXCAVATION/DISPOSAL WITH IN-SITU TREATMENT……………………………………………………………………………….………….….4-38

TABLE 4.1.3.3 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 AIR SPARGING/SOIL VAPOR EXTRACTIO…………………………………………………………………….………………………………………………..4-42

TABLE 4.1.3.4 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 GROUNDWATER/LNAPL MONITORING……………………………………………………………………………………………………..……….….4-44

TABLE 4.1.3.5 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER……………………………………………………………………………………………………………………….….4-48

TABLE 4.1.3.6 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 SOIL VAPOR/SVI MONITORING …………………………………………………………………………………………………………………………………….….4-50

TABLE 4.1.3.7 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 IMPLEMENT ECS AND ICS …………………………………………………………………………………………………………………………………….….4-52


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LIST OF TABLES (CONTINUED)


TABLE 4.1.4.1 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 SOIL AND LNAPL EXCAVATION AND DISPOSAL……………………………………………………………………………………………………………………..….4-62

TABLE 4.1.4.2 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 LNAPL PHYSICAL BARRIERS AND EXTRACTION/DISPOSAL……………………………………………………………………………………………….….4-66

TABLE 4.1.4.3 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 AIR SPARGING/SOIL VAPOR EXTRACTION/THERMAL TREATMENT …………………………………………………………………….…….….4-69

TABLE 4.1.4.4 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 GROUNDWATER/LNAPL MONITORING………………………………………………………………………………………………………..…….….4-72

TABLE 4.1.4.5 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER……………………………………………………………………………………………………………………….….4-75

TABLE 4.1.4.6 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 SOIL VAPOR/SVI MONITORING …………………………………………………………………………………………………………………………………….….4-77

TABLE 4.1.4.7 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 IMPLEMENT ECS AND ICS……………..….4-79


TABLE 4.1.5.1 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 LNAPL PHYSICAL BARRIERS AND EXTRACTION/DISPOSAL……………………………………………………………………………………………….….4-90

TABLE 4.1.5.2 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 THERMAL CONDUCTIVE HEATING WITH IN-SITU CHEMICAL OXIDATION………………………………..……………………………………………………….….4-95

TABLE 4.1.5.3 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 TARGETED SOIL EXCAVATION/DISPOSAL …………………………………………………………………………………………………………………………………….….4-96

TABLE 4.1.5.4 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 AIR SPARGING/SOIL VAPOR EXTRACTION/THERMAL TREATMENT …………………………………………………………………………….4-100

TABLE 4.1.5.5 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 GROUNDWATER/LNAPL MONITORING………………………………………………………………………………………………...………….….4-102

TABLE 4.1.5.6 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER…………………………………………………………………………………………………………………….….4-106

TABLE 4.1.5.7 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 SOIL VAPOR/SVI MONITORING …………………………………………………………………………………………………………………………….…….….4-108

TABLE 4.1.5.8 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 IMPLEMENT ECS AND ICS…………………………………………………………………………………………………………………………….….4-109

TABLE 4.1.5.9 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5…………………………………………………….….4-121

TABLE 4.2.1 EVALUATION OF REMEDIAL ALTERNATIVES…………………………………………………………………….….4-123

TABLE 4.2.2 ESTIMATED COSTS FOR RECOMMENDED REMEDIAL ALTERNATIVE 5……………………………………………………………………………………………….……………………………….….4-128

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LIST OF FIGURES


FIGURE 1.1.1 SITE AREA MAP ……………………………………………………………………………………………..……………………1-2

FIGURE 2.2.3.1 UTILITY SURVEY …………………………………………………………………………………………………………………2-13

FIGURE 2.2.4.1 WATER TABLE ELEVATIONS, APRIL 2015……………………………………………………………………………2-16

FIGURE 2.2.4.2 WATER TABLE ELEVATIONS, NOVEMBER 2015 …………………………………………………………………2-17

FIGURE 2.2.5.1 CROSS-SECTION LOCATION MAP……………………………………………………………………….………………2-20

FIGURE 2.2.5.2 WI-EL CROSS-SECTION ………………………………………………………………………………………………………2-21

FIGURE 2.2.5.3 W2-E2 CROSS-SECTION ……………………………………………………………………………………………………2-22

FIGURE 2.2.5.4 NE1-SW1 CROSS-SECTION…………………………………………………………………………………………………2-23

FIGURE 2.2.5.5 NW-SE CROSS-SECTION ……………………………………………………………………………………………………2-24

FIGURE 2.2.5.6 SW2-NE2 CROSS-SECTION…………………………………………………………………………………………………2-25

FIGURE 2.2.6.1 AREAL EXTENT OF PCBS IN LNAPL………………………………………………………………………...………..…2-31

FIGURE 4.1.2.1 ALTERNATIVE 2 AS/SVE SYSTEM LAYOUT……………………………………………………………………….……4-5

FIGURE 4.1.2.2 ALTERNATIVE 2 OFF-SITE PHYSICAL BARRIER AND LNAPL EXTRACTION LAYOUT……………..…4-7

FIGURE 4.1.2.3 ALTERNATIVE 2 GROUNDWATER/LNAPL MONITORING NETWORK LAYOUT………………………4-12

FIGURE 4.1.2.4 ALTERNATIVE 2 SOIL VAPOR/SVE MONITORING LAYOUT …………………………………….……………4-15

FIGURE 4.1.2.5 ALTERNATIVE 2 LIMITED ON-SITE REMOVALS………………………………………………………….……… 4-18

FIGURE 4.1.3.1 ALTERNATIVE 3 PHYSICAL BARRIER/LNAPL EXTRACTION LAYOUT…………………………..…………4-28

FIGURE4.1.3.1A ALTERNATIVE 3 OPTION: ISS OF LNAPL LAYOUT…………………………………………….…………………4-32

FIGURE 4.1.3.2 ALTERNATIVE 3 TARGETED SOIL EXCAVATION AREAS …………………………..……………………………4-36

FIGURE 4.1.3.3 ALTERNATIVE 3 AS/SVE SYSTEM LAYOUT…………………………………………………………………....……4-40

FIGURE 4.1.3.4 ALTERNATIVE 3 GROUNDWATER/LNAPL MONITORING NETWORK LAYOUT………………...……4-43

FIGURE 4.1.3.5 ALTERNATIVE 3 SSDS LAYOUT……………………………………………………………………………………………4-46

FIGURE 4.1.4.1 ALTERNATIVE 4 SOIL AND LNAPL EXCAVATION AREA ………………………..………………………………4-59

FIGURE 4.1.4.2 ALTERNATIVE 4 PHYSICAL BARRIERS/LNAPL EXTRACTION LAYOUT……………………………………4-63

FIGURE 4.1.4.3 ALTERNATIVE 4 AS/THERNNAL/SVE SYSTEM LAYOUT…………………………..……………………………4-67

FIGURE 4.1.4.4 ALTERNATIVE 4 GROUNDWATER/LNAPL MONITORING NETWORK LAYOUT………………………4-70

FIGURE 4.1.4.5 ALTERNATIVE 4 SSDS LAYOUT……………………………………………………………………………………………4-74

FIGURE 4.1.5.1 ALTERNATIVE 5 GROUNDWATER CUTOFF WALL/ LNAPL EXTRACTION LAYOUT…………………4-89

FIGURE 4.1.5.2 ALTERNATIVE 5 IN-SITU THERMAL TREATMENT/CHEMICAL OXIDATION SYSTEM LAYOUT…4-93

FIGURE 4.1.5.3 ALTERNATIVE 5 CONCEPTUAL DESIGN OF THERMAL CONDUCTIVE HEATING ……………………4-94

FIGURE 4.1.5.4 ALTERNATIVE 5 AS/THERNNAL/SVE SYSTEM LAYOUT……………………………………………..…………4-99

FIGURE 4.1.5.5 ALTERNATIVE 5 GROUNDWATER/LNAPL MONITORING NETWORK LAYOUT……………………4-101

FIGURE 4.1.5.6 ALTERNATIVE 5 SSDS LAYOUT…………………………………………………………………………………….….4-105

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APPENDICES

APPENDIX A REMEDIAL INVESTIGATION REPORT FIGURES AND UPDATED REMEDIAL INVESTIGATION TABLES 3 AND 4

APPENDIX B SUPPORTING INVESTIGATION REPORTS (ON CD): Product Testing Report, Test Pit Report, Survey (BL Companies, October 26, 2015, Updated March 18, 2016), NYCDPW May 1946 Contract No. 16 Drawing, NYCDEP Water Mapping, 3/5/2013, Water Level Data, Laboratory Reports – Product Testing for PCBs

APPENDIX C FEASIBILITY STUDY COST ESTIMATES

APPENDIX D THERMAL TREATMENT CASE STUDIES IN DENSE URBAN AREAS

APPENDIX E THE CURRENT SITE ELECTRICAL INFRASTRUCTURE LOCATIONS

APPENDIX F CASE STUDY FOR CHEMICAL OXIDATION OF PHTHALATES

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LIST OF ACRONYMS

Acronym Definition

ARARs Applicable or Relevant and Appropriate Requirements AS Air Sparging

AST Aboveground Storage Tank

C&D Construction & Demolition

CAMP Community Air Monitoring Plan

CERCLA Comprehensive Environmental Response, Compensation and Liability Act of 1980

CFR Code of Federal Regulations

CHASP Construction Health and Safety Plan

CO Certificate of Occupancy

CVOC Chlorinated Volatile Organic Compound

DEHP bis(2-ethylhexyl) phthalate

DOP di-n-octyl phthalate

EC Engineering Control

ELMS Electronic Information Management System

ELAP Environmental Laboratory Accreditation Program

ERH Electrical Resistivity Heating

ESA Environmental Site Assessment

FDNY New York City Fire Department

FPM FPM Engineering Group, P.C.

FS Feasibility Study

GPR Ground Penetrating Radar

GRA General Response Action

HASP Health and Safety Plan

IBC Intermediate Bulk Container

IC Institutional Control

IDW Investigation Derived Waste

_, IRM Interim Remedial Measure

ISS In-Situ Stabilization

K Hydraulic Conductivity

LNAPL Light Non-Aqueous-Phase Liquid

MSL Mean Sea Level

NYC DEP New York City Department of Environmental Protection

NYCRR New York Code of Rules and Regulations

NYC OER New York City Office of Environmental Remediation

NYSDEC New York State Department of Environmental Conservation

NYSDOH New York State Department of Health

NYSDOT New York State Department of Transportation

OSHA United States Occupational Health and Safety Administration

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Acronym Definition

PAHs Polycyclic Aromatic Hydrocarbons PBS Petroleum Bulk Storage

PCBs Polychlorinated Biphenyls

PE Professional Engineer

PID Photoionization Detector

PPE Personal Protective Equipment

QEP Qualified Environmental Professional

RAO Remedial Action Objective

RAP Remedial Action Plan

RCA Recycled Concrete Aggregate

RCRA Resource Conservation and Recovery Act

RI Remedial Investigation

ROD Record of Decision

ROI Radius of Influence

RR Restricted Residential

SCFM Standard Cubic Feet per Minute

SCGs Standards, Criteria and Guidance

SCOs Soil Cleanup Objectives

SMP Site Management Plan

SPDES State Pollutant Discharge Elimination System

SSDS Sub-Slab Depressurization System

SVE Soil Vapor Extraction

SVI Soil Vapor Intrusion

SVOCs Semivolatile Organic Compounds

USCS Unified Soil Classification System

USGS United States Geological Survey

UST Underground Storage Tank

UU Unrestricted Use

TAGM Technical Administrative Guidance Memorandum

TAL Target Analyte List

TCE Trichloroethylene

TCH Thermal Conductive Heating

TCL Target Compound List

VOCs Volatile Organic Compounds

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1.0 INTRODUCTION AND BACKGROUND INFORMATION

This Feasibility Study (FS) Report has been prepared by Goldberg Zoino Associates of New York, P.C. d/b/a GZA GeoEnvironmental of New York. (GZA) on behalf of Dupont Street Developers, LLC (Client) for New York State Department of Environmental Conservation (NYSDEC) Inactive Hazardous Waste Disposal Site #224136, identified as the Former NuHart Plastic Manufacturing Site located at 280 Franklin Street, Brooklyn, New York (Site). This FS Report was prepared to evaluate potential remedial alternatives for the Site. GZA has relied on the earlier work developed and certified by FPM Engineering Group, P.C in developing this Addendum to the April 2016 Feasibility Study including the Remedial Investigative Report (Ecosystems Strategies, Inc., July 30, 2015), the “Supplemental Remedial Investigative Report” (October 2015) and the “Feasibility Study Report for Former NuHart Plastic Manufacturing Site, 280 Franklin Street, Brooklyn, New York, NYSDEC Site #224136” April 2016, and other NYSDEC-approved investigations completed for the Site and off-site vicinity. The revised FS has incorporated many aspects of the previous FS submitted by FPM including data, tables, appendices, and approach. This Feasibility Study addresses the comments received from the NYSDEC in correspondence dated December 5, 2016, the NYSDEC meeting on January 9, 2017, and references additional investigations performed following the October 2015 RI which are addressed in Section 2.

1.1 SITE LOCATION AND DESCRIPTION

The subject Site is identified as the Former NuHart Plastic Manufacturing Site located at 280 Franklin Street in the Greenpoint area of Brooklyn, New York 11222 and is owned by Dupont Street Developers LLC. The approximately one-acre Site (240 feet by 200 feet) is identified on the Brooklyn Borough tax map as Block 2487, and Lots 1, 10, 12, 72 and 78, as shown on the Site Location Map (Figure 1.1.1). The Site is comprised of the western portion of a vacant industrial building complex (the former NuHart Plastic manufacturing facility).

The Site is bordered to the north by Clay Street, to the west by Franklin Street, to the south by Dupont Street, and to the east by other portions of the former NuHart Plastic manufacturing facility (Lots 17, 18, 20, 21, and 57), as shown on Figure 1.1.1. To the north are commercial and industrial buildings. Across Franklin Street to the west is a New York City park (Greenpoint Playground). Across Dupont Street to the south are multifamily residences. Across the intersection of Franklin Street and Dupont Street to the southwest is a vacant property which may be redeveloped for use as a school.

The Site is entirely covered by a network of adjoining industrial buildings that were constructed at different times. The Site is underlain by sub-grade footings, utility networks, closed underground storage tanks (USTs), and piping and trench systems. The USTs and trench systems were cleaned out and the USTs were closed in accordance with applicable regulations in 2006. The Site is serviced by the municipal water service and a municipal sewer system.

Former industrial operations at the Site has impacted on-site and off-site soil and groundwater with phthalates and lubricating oil (Hecla oil), most likely released from the tank and piping/trench systems. Phthalates and a phthalate/oil mixture are present in soil and as a light non-aqueous-phase liquid (LNAPL)

SHEET NO.

GZA GeoEnvironmental, Inc.Engineers and Scientists

PREPARED BY: PREPARED FOR:

www.gza.com

PROJECT NO.DATE: REVISION NO.DESIGNED BY:

PROJ MGR:

DRAWN BY:

REVIEWED BY: CHECKED BY:

SCALE:

280 FRANKLIN STREETBROOKLYN, NEW YORK

SITE AREA MAP

DUPONT STREETDEVELOPERS, LLC

AUGUST 2016 12.0076485.00

FIGURE

1.1.1JB

ZS

ZS

MT

JB

NOT TO SCALE

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plume floating on the groundwater surface primarily beneath Lots 1, 10, and 78 of the Site and extending somewhat off-site to the southwest. Dissolved groundwater contamination is generally limited to phthalates and localized impacts by chlorinated solvents. The chlorinated solvent release area appears to be in or near Lot 12 in the northeastern portion of the Site.

The Site was added to the NYSDEC's Registry of Inactive Hazardous Waste Disposal Sites (State Superfund Registry) in July 2010. Ongoing investigation and remediation activities are overseen by the NYSDEC and the New York State Department of Health (NYSDOH).

1.2 SITE ENVIRONMENTAL SETTING

The Site environmental setting is described in detail in the RI Reports (Ecosystems Strategies, Inc., July 30, 2015) and Supplemental Remedial Investigation Report, (FPM October 2015) and are summarized herein. Additional details are presented in Section 2.2.5. The Site is in a relatively level urban setting with surface elevations ranging from 17 to 23 feet above mean sea level (MSL). The Site is situated on a regional north-northwest trending topographic ridge bounded by the East River to the west and Newtown Creek to the north and east. There is a gradual downward slope to the west-northwest, towards the confluence of the nearby East River and Newtown Creek.

The soil type at the Site is mapped as Urban Land, which is defined as areas that are more than 80 percent covered by buildings and pavements. The Site surface (which is entirely covered by building slabs) is underlain by historic fill in some areas to depths of nearly 20 feet.

Native materials are present beneath the historic fill and are identified as unconsolidated Upper Pleistocene glacial deposits by the U.S. Geological Survey (USGS Open-File Report 92-76, 1995). On-site, these deposits were described in the RI Report as sandy soil with some gravel to between 10 and 12 feet below grade, below which silt and clay intervals are present. The top of a nearly continuous thick clay layer is found between 8 and 23 feet below grade. This clay was not fully penetrated by any of the borings performed during the RI but was noted to extend to approximately 50 feet below grade in geotechnical borings performed on-site in 2014. The clay was noted to be absent in one geotechnical boring near the southwest corner of the Site.

The glacial deposits rest unconformably on top of Precambrian crystalline bedrock, the top of which is found at an approximate elevation of -50 feet MSL in the project vicinity (USGS Open-File Report 9276, 1995). This published information is consistent with the on-site geotechnical borings, which encountered bedrock at approximately 60 feet below the Site surface (-40 +/- feet MSL). Bedrock was not encountered in any of the borings performed during the RI (maximum depth of 30 feet).

Groundwater beneath the Site is generally found within the fill or glacial deposits at a depth noted in the RI Report as 7 to 12 feet below grade, with the highest water table generally occurring during the winter. Groundwater flow is generally westerly to northwesterly, towards the East River (located approximately 450 feet west of the Site) and is somewhat tidally-influenced to the west and northwest of the Site.

1.3 SITE HISTORY

The Site was developed in the 1800s and was used up to 1950 for manufacturing purposes, including metal-working and manufacture of light fixtures, soap, and water-proofing materials. From 1950 until 2004 the Site and associated manufacturing buildings to the east were used for production, storage, and

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shipping of plastic and vinyl products. Operations ceased in 2004 and the Site buildings have not been used since that time. Redevelopment of the Site and associated former NuHart buildings to the east is being contemplated. Redevelopment of the Site is anticipated to include restricted residential and/or commercial uses.

Prior Site investigations are summarized in Section 2.

Seventeen USTs and associated sub-grade pipe trenches were cleaned out and closed in place in 2006; this work was reported to the NYSDEC. The tanks include 8 USTs formerly containing plasticizers (phthalates) and 4 USTs containing "Super Hecla" oil (a heavy-weight machine lubricant) located on-site and 5 USTs (3 fuel oil tanks and 2 chemical tanks containing methyl tert-butyl ketone and acetone) located off-site to the east in the associated NuHart manufacturing buildings. Spill #0601852 was reported to the NYSDEC for a petroleum release associated with the fuel oil USTs.

LNAPL recovery has been ongoing since 2006 as an Interim Remedial Measure (IRM). LNAPL is removed from several wells within and in proximity to the Site building and is transported for off-site disposal. LNAPL recovery appears to be limited by its moderate to highly viscosity.

Groundwater monitoring has been performed for petroleum compounds and phthalates, although recent monitoring events have included chlorinated volatile organic compounds (VOCs).

The Site was added to the NYSDEC's Registry of Inactive Hazardous Waste Disposal Sites (State Superfund Registry) in July 2010. Investigation and remediation activities since that time have been overseen by the NYSDEC and NYSDOH. These activities have included completion of an Interim Investigation, an RI, and a Supplemental RI, IRM LNAPL monitoring and removal, groundwater monitoring, and additional delineation investigations. The results of the investigation activities are summarized in Section 2. This information was used to evaluate the feasibility of potential remedial measures described later in this report.

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2.0 SUMMARY OF NATURE AND EXTENT OF CONTAMINATION AND POTENTIAL EXPOSURES, ADDITIONAL INVESTIGATIONS

2.1 NATURE AND EXTENT OF CONTAMINATION AND POTENTIAL EXPOSURES

The nature and extent of contamination associated with the Site were described in Section 3 of the RI Report and Section 4 of the Supplemental RI Report (FPM, October 2015) and are summarized below. Clarifying information has been added where needed to depict the nature and extent of Site-related impacts. Figures depicting the nature and extent of contaminants in on-site and off-site media were presented in the RI Report and are included in this section for reference.

A qualitative human health exposure assessment is included in Section 3.6 of the RI Report and additional information concerning potential exposure to Site-related contaminants is included in the Supplemental RI Report. Relevant information concerning potential exposure to Site-related contaminants is summarized in this section.

2.1.1 Soil

Soil results presented in the RI Report were compared to the Title 6 of the New York Codes, Rules and Regulations (6 NYCRR) Subpart 375-6 Soil Cleanup Objectives (SCOs) for unrestricted use (UU) and for the lowest contemplated use of the property (restricted residential, or RR). These results are presented in Tables 3 through 9 in the RI Report. Key results are also summarized in Figures 6, 7 and 8 in the RI Report, copies of which are included in Appendix A.

As requested by the NYSDEC, for the purposes of this FS, the soil results were also compared to the SCOs for the protection of groundwater (GW) found in 6 NYCRR Subpart 375-6 (Table 375-6.8(b)) and in the NYSDEC's CP-51 Soil Cleanup Guidance Policy. This comparison was performed for those Site-related contaminants found in groundwater (phthalates and chlorinated solvent VOCs) and the results are shown on Tables 3 and 5 included in Appendix A.

VOCs

Trichloroethylene (TCE) and related chlorinated solvents were detected at levels below the RR-SCOs, but above the UU-SCOs in a limited solvent "hot spot" area in the northeastern portion of the Site, as shown on Figure 6 in Appendix A. This "hot spot" extends slightly off-site beneath the sidewalk on the south side of Clay Street, but does not extend to the north side of Clay Street, to the east of the Site, or to the west of soil boring 3SB-5. The impacted soil has been identified only at depth (generally 10 to 25 feet bgs). Soil above 10 feet bgs did not exhibit detections of chlorinated solvent VOCs in excess of the UU-SCOs, with the only exception being soil in the 0 to 5-foot interval of on-site soil boring 2SB-2.

As the GW-SCOs for chlorinated solvents are the same as the UU-SCOs, the area where TCE and related chlorinated solvents in soil exceed the GW-SCOs is the same — that is, a limited solvent "hot spot" area in the northeastern portion of the Site, as shown on Figure 6 in Appendix A.

A limited number of other VOCs, (acetone, xylenes, and 1,2,4-trimethylbenzene) were found above the UU-SCOs, but below the RR-SCOs, in soil at other locations on the Site, as shown on Figure 6. Two acetone detections above the UU-SCOs and below the RR-SCOs were also noted beneath the former NuHart facility

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to the east of the Site and acetone was detected above the UU-SCO at one location beneath the sidewalk to the north of the Site.

SVOCs

Semivolatile organic compound (SVOC) soil contamination (analyte levels above the RR-SCOs) on-site is limited to bis (2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP) in soil located at and near the groundwater interface in the area where LNAPL is present, as shown in Figure 8 in Appendix A. As the GW-SCOs for these two phthalates are higher than the RR-SCOs (due to the low solubility of these compounds), the area where soil contamination levels for DEHP and/or DOP exceed the GW-SCOs is somewhat more limited, but generally includes a similar area.

Soil contamination associated with DEHP and/or DOP is found in off-site soil located at and near the groundwater interface in the area where LNAPL is present, generally to the west and southwest of the Site, as shown in Figure 8. The interval of impacted soil is found only at depth (approximately 8 to 10 feet bgs). The phthalate concentrations were noted to exceed the RR-SCOs (and in some cases the GW-SCOs) at limited locations where LNAPL is present or in close proximity to the affected soil.

None of the other phthalate detections were noted to exceed any of the SCOs.

Metals

Several metals were detected in excess of the UU-SCOs in on-site soil, including chromium, copper, iron, lead, nickel, and/or selenium, as noted on Table 7 in the RI Report. These detections are very similar to those detected in off-site soil (chromium, iron, nickel, selenium, and/or zinc). None of the detections in on-site or off-site soil exceeded the RR-SCOs with the exception of iron. These detections are most likely related to materials in the historic fill and are characteristic of historic fill commonly found in the New York City metropolitan area. Neither the distribution of these detections, nor the levels of the detections, is indicative of a release of metals contaminants at the Site. It was noted that the iron detections may also result from natural background conditions as iron is commonly found at somewhat elevated levels in native soil in this area.

As these metals are not related to a release on the Site, specific measures to remediate metals in soil will not be considered in this FS. However, proper management of soil containing metals during remedial activities, and associated Health and Safety Plan (HASP) and Community Air Monitoring Plan (CAMP) monitoring, will be addressed.

Discussion

Direct contact, ingestion and/or inhalation of airborne soil particles are the pathways by which humans may be exposed to soil. At present, the Site is fully covered by the Site building foundation and following the future redevelopment of the Site it is highly likely that the entire Site surface will continue to be covered with a building foundation and/or pavement. Therefore, there is no reasonable possibility for Site occupants, visitors or trespassers to be exposed to Site soil at present or following future redevelopment. Similarly, at present the off-site soil impacted by Site-related contaminants (phthalates and TCE and related chlorinated solvents) is covered by road or sidewalk pavement and found only at depth (8 feet bgs or deeper). This soil is anticipated to remain at depth and covered by pavement except during ground intrusive activities. Therefore, there is no reasonable possibility for residents or visitors in off-site areas to be exposed to off-site soil at present or in the future.

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It is possible that human contact with on-site and/or off-site soil could occur during ground-intrusive work or if dust containing the impacted soil is generated during intrusive activities. Ground-intrusive activities will be likely during remedial and redevelopment activities at the Site and may occur during construction activities in off-site areas. Site-related remedial activities are anticipated to be conducted under a HASP and a CAMP designed to monitor and control potential exposures to impacted soil. Therefore, human exposure to impacted soil is unlikely to occur during intrusive remedial or redevelopment activities conducted under a Site-specific HASP and CAMP. Potential measures to control exposures to off-site soil during construction activities will be addressed in this FS.

2.1.2 Groundwater

Groundwater results for dissolved constituents presented in the RI Report were compared to the NYSDEC's Class GA Ambient Water Quality Standards (Standards). These results are presented in Tables 10 through 13 in the RI Report. Key groundwater results are also summarized in Figures 9 through 13 in the RI Report, copies of which are included in Appendix A

LNAPL Plume

Phthalates and lubricating oil (Hecla oil), most likely released from the Site's tank and piping/trench systems, are present as an LNAPL plume floating on the groundwater surface. The LNAPL plume is present beneath much of the Site, particularly in the western half of the Site where most of the phthalate and lubricating oil-related infrastructure was present, as shown on Figure 13 from the RI Report (Appendix A). The LNAPL plume extends off-site to the west and southwest, including beneath the east side of Franklin Street, the north side of Dupont Street, and across these streets somewhat to the northwest and southeast corners of the Franklin/Dupont intersection. LNAPL has also been found in one off-site well (MW-7) on the south side of Clay Street. LNAPL does not extend as far as the playground to the west of the Site, the vacant property to the southwest of the Site, or across Clay or Commercial Streets, based on repeated measurements in the off-site wells in these areas starting in 2006 and conducted on a monthly basis over the past four years. Additional information concerning the LNAPL properties and apparent thickness is presented in Section 2.2 below.

VOCs

TCE and related chlorinated VOCs associated with the Site are present in groundwater beneath the northeastern portion of the Site and extend a short distance off-site to the north-northwest, as shown on Figure 10 from the RI Report (Appendix A). The highest concentrations of chlorinated VOCs are detected at on-site well MW-34 and off-site wells MW-8 and MW-40, located immediately north and east, respectively, of the apparent source area on the northeastern portion of the Site. Chlorinated VOC concentrations decrease significantly to the east, west, and south of these wells, with more moderate decreases noted to the northwest.

SVOCs

Phthalates, including primarily DEHP and one detection of DOP, were detected above NYSDEC Standards in several wells generally located on the periphery of the area where LNAPL is present, including off-site wells to the east, south, and southwest of the Site, as shown on Figure 11 from the RI Report (Appendix A). DEHP was also detected in groundwater in three wells located off-site to the northeast, in proximity to the off-site portion of the former NuHart facility. Phthalates were not detected above the NYSDEC Standards in groundwater in wells located to the west or northwest of the Site.

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Metals

Several metals were detected in unfiltered groundwater samples in excess of the NYSDEC Standards, including sodium in all 16 samples (34.9 to 311 mg/I), iron (0.899 to 9.38 mg/I in 9 samples), and magnesium (39.4 to 80.1 mg/I in 5 samples). As noted in the RI Report, these detections may be related to suspended particulates in the unfiltered samples and/or ambient groundwater quality in the Site vicinity and do not indicate Site-related metals impacts to groundwater. Accordingly, remediation of metals in groundwater is not considered in this FS. It should be noted that the sodium levels in all of the samples exceed the NYSDEC's sodium Standard of 20 mg/I for fresh (Class GA) groundwater and likely result from the Site's proximity to nearby saltwater surface water bodies, as well as the Site's original near-shore location prior to filling and development.

Discussion

Direct contact and/or ingestion are the primary pathways by which humans may be exposed to groundwater. The Site area is served by the public water supply and no private water supply wells are reported to exist in the vicinity of the Site. As noted above, the sodium content of the groundwater precludes use of the groundwater for potable water purposes unless desalinization is performed. As groundwater is saline and is not being used for drinking water or any other purpose at the Site or in nearby off-site areas, there is no reasonable possibility for Site occupants or visitors or area residents to be exposed to Site-related contaminants in groundwater.

It is possible that human contact with Site-related contaminants in groundwater could occur during ground-intrusive work that extends to the depth of the water table (generally 8 feet or more bgs) in the areas where such contaminants are present. Ground-intrusive activities that may extend to the groundwater will be likely during Site-related remedial activities and may occur during construction activities in on-site and off-site areas. The Site-related remedial activities and on-site construction activities are anticipated to be conducted under a HASP and a CAMP designed to monitor and control potential exposures to contaminated groundwater. Therefore, human exposure to impacted groundwater is unlikely to occur during intrusive remedial or construction activities. Potential measures to control exposures to off-site groundwater during construction activities will be addressed in this FS. It should be noted that groundwater conditions are anticipated to improve as a result of remedial activities for Site-related contamination. Therefore, over time the potential for exposure to Site-related contaminants in groundwater during ground-intrusive activities is likely to diminish.

2.1.3 Soil Vapor, Sub-Slab Soil Vapor and Indoor/Outdoor Air

Soil vapor impacted by TCE and related CVOCs is present beneath the northeastern portion of the Site building, with the greatest impacts coinciding with CVOC-impacted groundwater in this area. The impacts do not extend fully beneath the Site and are not found beneath the western or southern portions of the Site, as shown in Figure 3.2.4.1 in Appendix A.

CVOCs in soil vapor are present off-site in a limited area to the east and north of the Site, generally consistent with the CVOC distribution in groundwater. Site-related CVOC soil vapor impacts extend off-site to the east beneath a portion of the adjoining former NuHart facility, but do not extend to the east end of this building or to the vicinity of residential properties to the east of the Site.

Site-related CVOC soil vapor impacts extend to the north, across Clay Street, but do not extend as far northward as the north side of Commercial Street, as demonstrated by soil vapor data from Greenpoint

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Landing. In general, the impacts decrease to the east and west of the 3SB-1 location on the north side of Clay Street. The distribution of TCE on the north side of Clay Street east of 3SB-1 suggests that it is possible that there is an off-site TCE source (unrelated to the Site) on the north side of Clay Street.

Other VOCs were detected in soil vapor throughout the Site and vicinity at generally low levels consistent with typical urban settings with historic industrial uses. Some petroleum-related VOCs may be associated with the known petroleum spill located on the former NuHart facility just to the east of the Site and additional off-site petroleum vapor detections on the north side of Clay Street may be associated with an off-site source.

Discussion

Potential exposure pathways for soil vapor include inhalation within buildings in which soil vapor intrusion (SVI) is occurring and inhalation of soil vapor that may be released during intrusive activities into materials containing VOCs. SVI exposures at the Site under current conditions are likely to be insignificant as the building is not occupied. A CAMP would be implemented at the Site (and, as required, at off-site areas) during intrusive remedial activities to monitor air quality and minimize potential exposures to vapors for both construction workers and the public.

On-site remedial activities are anticipated to decrease the potential for SVI and redevelopment activities would, if necessary, include SVI mitigation measures to eliminate or significantly reduce the potential for SVI on-site. These mitigation measures are considered in this FS.

The off-site soil vapor sampling results suggest that SVI is a potential concern for off-site properties at 15 and 29 Clay Street. However, the potential for SVI at these properties cannot be confirmed unless access for SVI sampling is provided by the property owners. SVI may also present a concern at 48 Commercial Street if a building is constructed on this property in the future (the property presently does not include a building). Remedial activities to be conducted for the Site are likely to reduce the source of TCE and related CVOC vapors. Over time, source reduction is likely to reduce the potential for SVI in off-site buildings. Potential measures to control exposures to off-site soil vapor during construction activities and to address potential SVI into off-site buildings are addressed in this FS.

2.2 ADDITIONAL INVESTIGATIONS

FPM conducted additional investigations which were previously reported to the NYSDEC (FPM, February 23, 2015 and FPM, May 28, 2015) and are summarized in Sections 2.2.1 and 2.2.2 herein; copies of these supporting investigation reports are included in Appendix B. A plume consisting of phthalates and machine oil (Hecla oil) is present as an LNAPL floating on the groundwater surface. Investigations of the LNAPL have been performed to evaluate its properties and actual thickness in the formation. FPM’s investigations were performed to provide information for use in assessing potential remedial measures for the Site-related LNAPL.

An investigation of the locations and depths of utilities present in the off-site vicinity of the Site was conducted by FPM (appended to this report) for the purposes of providing information needed to evaluate potential remedial measures and for assessing potential migration pathways for Site-associated LNAPL. This survey also included measuring the elevations of the top of casing of the Site-related wells to assist with further evaluation of the groundwater flow directions in the Site vicinity. This survey is included in Appendix B and the results are discussed in Section 2.2.3 below.

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Existing water level measurements from the ongoing IRM activities were integrated with the newly-obtained well survey data by FPM to more fully evaluate the groundwater flow directions in the Site vicinity under seasonal conditions. This evaluation is presented in Section 2.2.4 and copies of the groundwater monitoring data used during this evaluation are included in Appendix B.

Existing boring logs from previous investigations of the Site and vicinity were presented by FPM and reviewed by GZA to evaluate the stratigraphic framework beneath the Site and assess potential relationships between the stratigraphy, the Site infrastructure, subsurface utilities, and the distribution of Site-related contaminants. This evaluation is presented in Section 2.2.5.

An evaluation of the nature of the wastes that may be produced during Site-related remedial activities was performed by FPM and reviewed by GZA. This evaluation is presented in Section 2.2.6. Additional testing of the LNAPL was also performed following identification of low-level polychlorinated biphenyls (PCB) contamination in waste LNAPL removed during the IRM; the results of this testing are also included in Section 2.2.6.

2.2.1 LNAPL Testing — Assessment of Well Conditions, Migration Rate, Viscosity

Several of the wells containing LNAPL were video-taped by FPM under pumping and recovery conditions to assess whether the PVC well screens and/or casings may be affected by contact with the LNAPL. None of the video testing results showed any apparent distortions of the well casings or screens, widening or obstruction of the screen slots, restriction of groundwater or LNAPL flow into the wells, encrustations or growths adhering to the casings or screens, or other conditions that may affect the integrity of the wells or well screens, or the flow of fluids into the wells. This information supports the continued use of Schedule 40 PVC well materials at this Site for monitoring or other purposes that do not typically require use of alternate well materials, and indicates that the data obtained from these wells is anticipated to be valid.

FPM observed the presence of sand at RW-8 and RW-10 which suggested that additional measures may be necessary to preclude sand intrusion into future wells if such wells are used for LNAPL recovery purposes. These measures may include reducing the screen slot and/or gravel pack size, more intensive well development, or some combination of these measures.

FPM evaluated the hydraulic conductivity (K) of the formation with respect to LNAPL using bail-down tests, with the recovery data used to evaluate the K of the formation relative to LNAPL. This analysis was performed using the Dagan solution (1978), which is a straight-line solution appropriate for partially-penetrating wells screened across the water table in an unconfined aquifer. The calculated K values for the LNAPL range from 1.099 x 10-6 to 8.991 x 10-6 feet/minute (ft/min). Sensitivity analyses were performed to assess the impact parameter selection on the calculated K values. In the case of these tests, the aquifer anisotropy ratio (ratio of vertical to horizontal hydraulic conductivity) was evaluated to have the most potential variability. The initial solutions utilized a typical aquifer anisotropy ratio of 0.1 (Todd, 1980). However, as the formation at the Site contains a significant amount of silt, a lower anisotropy ratio may be more appropriate. Additional solutions were calculated using an anisotropy ratio of 0.01 and demonstrated little change in the calculated K values.

Once the K values had been calculated, FPM integrated them with the groundwater gradient (1) values calculated from the water table contours previously presented in the RI Report to calculate the potential flow rate of the LNAPL under existing aquifer conditions. The calculated i values ranged from 0.002 to

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0.004. Using these i values and the range of K values, an LNAPL flow rate of between 2.2 x 10-9 and 3.6 x 10-7 ft/min was calculated. Converting these values to feet per year resulted in calculated LNAPL flow rates of between 0.0012 and 0.18 feet/year. At these low velocities, the LNAPL is essentially immobile. FPM noted that the calculated K values for the LNAPL include the effect of the water table recovery and, therefore, may be somewhat higher than actual K values for the LNAPL alone. This further supports the conclusion that the LNAPL is essentially immobile under existing conditions (low K and low i).

The calculated LNAPL flow rates were assessed relative to the presumed source(s) and known information concerning former Site operations and the extent of the LNAPL by FPM. The Site was used for plastic manufacturing from about 1950 until 2004 and the tanks, piping, and associated infrastructure were likely on-site since about 1950 as they were an integral part of the plastic manufacturing operations. The tanks, piping, and associated trench system were cleaned and closed in mid-2006. Based on this information, the releases that resulted in the presence of the LNAPL on the water table could have occurred during the 1950 to 2006 interval. Based on the apparent volume and extent of the LNAPL (including its extent in 2006) and its variable composition, FPM concluded that it was likely that the releases occurred from multiple sources and were ongoing for a number of years. Based on this data GZA believes that the high viscosity in low i values limits the off-site migration of the LNAPL.

The initial subsurface investigation of the Site, conducted in late 2006, included installation of many of the Site wells. At that time LNAPL was documented to be present beneath much of the western portion of the Site and extended downgradient to off-site wells MW-5 through MW-7, MW-15 and MW-16, but not to off-site wells MW-11 through MW-14 (none of the other off-site wells had been installed at this time). This information indicated that by late 2006, when the tanks and other potential sources of the releases were closed, the LNAPL was already present beneath much of the Site and had moved somewhat off-site, which suggests that the releases likely began early during the Site's history of plastic manufacturing and were likely ongoing for a number of years.

Additional wells have been added on several occasions and LNAPL monitoring and recovery have been ongoing since 2006. The monitoring data indicate that all wells that now contain LNAPL have contained LNAPL (or significant indications of LNAPL) since their installation. Wells that did not contain LNAPL (or exhibit significant indications of LNAPL) at the time of their installation still do not contain LNAPL. These observations suggest that there has been no apparent change in the configuration of the LNAPL plume since at least 2006.

FPM concluded that the extent of the on-site LNAPL and the variable nature of its composition (as discussed below) suggested that the LNAPL likely originated from several on-site releases. The majority of the tanks from which the releases may have occurred are located in the southwestern portion of the Site. This area is approximately 100 feet upgradient of the apparent location of the leading edge of the LNAPL at present. Using this information alone, a simple arithmetic calculation would suggest an LNAPL migration rate of between 1.7 and 3 feet a year. However, it should be recognized that initial LNAPL migration, particularly while a release is ongoing, is generally faster than later migration due to a number of factors, including driving forces during the release associated with continuous vertical columns of LNAPL extending from the release site to the water table surface, initial lateral expansion of the LNAPL mounds under gravitational forces, the likely lower viscosity of the released LNAPL before subsurface weathering processes further increased its viscosity. These factors typically result in an initial LNAPL migration rate that is higher than the migration rate that is observed later in the life of an LNAPL plume, after the release source is ended, the LNAPL has finished spreading out under gravitational forces, and the viscosity has increased due to weathering. Therefore, a sample arithmetic calculation of the LNAPL migration rate

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based on the locations of the apparent source(s) of the releases and the current downgradient edge of the LNAPL will not accurately represent the LNAPL's current migration rate under the forces that presently act on the LNAPL. In addition, factors such as organic content of the soils, adsorptive capacity of the soils and porosity all impact LNAPL migration rates.

FPM noted that LNAPL re-accumulated in the wells during both well screen integrity testing and bail-down testing. During both types of testing the fluid levels in the wells were drawn down to generally 2 to 5 feet below their static levels and recovery was very slow. This results in a very steep gradient (high i value) in proximity to the wellbore during much of each test. Based on the test information it was estimated by FPM that the induced i values in immediate proximity to the wells during testing may reasonably have ranged from 1 to 5. Using these induced i values, the calculated LNAPL velocity in immediate proximity to the wellbores during testing ranged from 0.6 to 236 feet per year. This information suggests that under high induced gradients (such as may result from significant groundwater pumping) the LNAPL may move more rapidly than under in-situ conditions where the actual gradient is very low. It should be noted that these velocities were mathematically calculated based on drawdown information from the immediate proximity of the wellbores during testing and, as such, may include wellbore effects that likely artificially increased the calculated velocities. It should also be noted that significant flow velocity increases would occur only if the induced gradient were significantly increased (by three orders of magnitude) over the normal very low gradient and if the induced gradient were to extend beyond the immediate area of the pumped wellbore, which is also unlikely. These conditions are highly unlikely to occur, and have not been observed at any time during LNAPL monitoring, even when dewatering was reportedly underway for nearby construction projects. We note that all the LNAPL observations over the past 10 years have shown the LNAPL plume to be static.

On February 23, 2015 FPM submitted a product testing report to the NYSDEC. The NYSDEC responded in a March 17, 2015 letter and disagreed with the report's conclusion that the LNAPL is stable. These issues are further discussed in Sections 3 and 4. In the product testing report, samples of LNAPL were obtained by FPM from several wells located throughout the LNAPL plume and were analyzed for kinematic viscosity over a range of temperatures, starting from the in-situ ground temperature (estimated at 55 degrees F) and proceeding in 10-degree F increments up to 125 degrees F. The resulting data indicated that the in-situ LNAPL kinematic viscosity under ambient conditions (about 55 degrees F) ranges from 28.25 mm2/s (or centiStokes) at on-site well MW-21 to 273.69 centiStokes at on-site well RW-8. At off-site well MW-5 the kinematic viscosity of the in-situ LNAPL was measured at 192.48 centiStokes. As the density of the LNAPL appears to be very close to 1, the calculated dynamic viscosity values for the in-situ conditions are similar, ranging from 27.12 to 262.74 mPas (or centiPoise). This data indicates that the in-situ LNAPL is viscous at 55 degrees F. For comparison, the in-situ LNAPL viscosity generally ranges between that of a light oil and a heavy oil. The viscous nature of this LNAPL is consistent with the calculated K values (discussed above) and with the calculated low flow rate of the LNAPL under in-situ conditions. FPM stated that although the LNAPL viscosity does decrease with increasing temperature, significant reductions in LNAPL viscosity were not achieved until higher temperatures (generally over 100 degrees F) are obtained and the LNAPL viscosity remained significantly above that of water throughout the entire range of temperatures tested. However, it is noted that the viscosity tests performed on the LNAPL in the range of 55F to 125F with 10-degree F increments to assess the effects of thermal conductive heating (TCH) on LNAPL viscosity. Heating was stopped by FPM at 125 degrees F as they believed this was a typical temperature range for in-situ thermal treatment. However, most TCH applications heat the groundwater and soils to 212-degree F (boiling point of water) or higher. The temperature range selected by FPM did not represent the temperature typical of TCH. Based on GZA’s review of the data, a significant drop in viscosity was observed from 180-200 mPas at 55F to 7 to 28 mPas at 125F (84% decrease of the viscosity).

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GZA’s review of the literature suggests that as the temperature is further increased beyond 125 degrees F, that viscosity will continue to decrease thereby increasing mobility of the LNAPL for extraction as described in the remedial alternatives presented below. FPM also reported literature viscosity values with temperature. Published information concerning the viscosity of phthalates (including the phthalate products reported to have been formerly used on-site) and Hecla oils (which are presently manufactured by ExxonMobil Oil Corporation), was obtained via a literature search. These data indicate that the viscosity of phthalate products is significantly higher than the viscosity of the groundwater on which the LNAPL is present and the viscosity of the Hecla oil is even higher than that of phthalates. Specifically, the published viscosity values for phthalate products at temperatures near the natural in-situ formation temperature (up to 77 degrees F) range from 55 to 80 centiPoise (or mPa s). Hecla oil viscosity is reported to range from 680 to 1,000 centiStokes (626 to 920 mPa s) at 104 degrees F (the lowest temperature for which data could be located). FPM further stated that, the in-situ viscosities for the LNAPL on the western side of the Site (RW-8 and RW-10) and off-site downgradient (MW-5) are higher than the published values for phthalates, but lower than the values for Hecla oil. These data suggest that the LNAPL in this area consists of a mixture of phthalates and Hecla oil, consistent with the locations of former underground storage tanks (USTs) that stored the products. The in-situ viscosity values may also be affected by weathering processes, which typically increase the viscosity of in-situ LNAPL relative to its original viscosity. It is noted that the viscosity of DOP in the literature was reported at 55 mPa s at 77F, which is comparable to the viscosities (16 - 85 mPa s) reported for the actual LNAPL mixtures from the Site at 75-80F. Moreover, the literature reported tests to 187 F and a viscosity drop down to 5 mPa s. A further temperature change would be expected after 125 F (51-degree C). TCH includes heating the groundwater and soils to up to 212F and therefore a further decrease in viscosity is expected in the range of less than 5 mPa sm. This would be in the range of a No 1 or 2 oil (or less).

2.2.2 LNAPL Depth and Thickness

Although LNAPL monitoring has been performed in Site wells for several years, the actual depth to LNAPL and thickness in the formation were not clearly understood due to processes that typically exaggerate the thickness of LNAPL observed in monitoring wells. Because of these processes, the thickness of LNAPL as measured in monitoring wells is typically noted as "apparent thickness".

FPM performed an additional investigation to obtain more information concerning the actual depth and thickness of the LNAPL in the formation at this Site. This included obtaining information concerning the depth to and visible thickness of the smear zone in the soil above and below the water table, the visible thickness of LNAPL on the water table surface, and subjective observations of LNAPL mobility, odor, and other features that may affect evaluation and implementation of remedial alternatives. This investigation included performing a test pit near the center of the LNAPL area and conducting a detailed examination of boring logs throughout the LNAPL area.

The following observations were noted by FPM from the test pit, which was performed in proximity to RW-12 near the southwest corner of the Site:

Although staining and odors typical of LNAPL were noted at two intervals in the test pit (top of clay at about 5.75 feet and about 12.5 feet below the top of the slab, just above the top of the LNAPL), no organic vapors were detected by the photoionization detector (PID). The odors were observed to be moderate in proximity to the removed stained materials, but were not perceived to extend beyond the immediate area of the test pit or the pile of excavated impacted soil placed adjacent to the test pit pile. Odor was not noticeable at a short distance from the stained materials. These observations

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suggest that odors from LNAPL-impacted materials that may be exposed during remedial activities may not present a significant concern.

Historic fill containing significant amounts of anthropogenic debris, ash, and cinders is present to a depth of about five feet below the top of the slab in the test pit area. Although this material did not exhibit any significant odors or staining, the visual appearance of the historic fill suggests that it is likely to contain constituents commensurate with its origin and the fill, if excavated, will likely require off-site disposal as regulated material.

Native soil, including silty fine sand and clay, is present beneath the historic fill to a depth of about 10.5 feet below the top of the slab in the test pit area. No visible indications of potential impacts were noted in this soil, with the exception of some minor staining and odor at the top of the clay; these impacts did not appear to extend significantly into the clay. This suggests that the soil beneath the Site slab and above the LNAPL smear zone is not likely to be impacted by the LNAPL except in areas where releases occurred and the LNAPL migrated downward from tanks, piping, trenches or other structures that formerly contained LNAPL.

Native material that appears to be glacial till (an apparently unsorted mixture of fine to coarse-grained materials ranging from silt up to cobbles) is present from about 10.5 feet to at least 14 feet below the top of the slab in the test pit area. This material is extremely loose and was noted to run into the test pit as each bucket of soil was removed. The behavior of this material suggests that shoring will be required for any excavations that penetrates this material.

A smear zone (stained soil with moderate odor but no LNAPL) was noted to extend from about 12.5 to 13.5 feet below the top of the slab in the test pit. LNAPL was encountered at 13.5 feet and extended to at least 14 feet below the top of the slab in the test pit. The LNAPL was noted to consist of dark brown oily fluid with an approximate consistency of used motor oil. The visible properties of the LNAPL observed in the test pit were consistent with the product testing results discussed above.

Depth to LNAPL and water measurements were obtained from the wells in the LNAPL area by FPM during the test pit procedure and were compared to the test pit observations. Boring logs throughout the LNAPL area were also reviewed to evaluate the depth and actual thickness observed in formation materials. The following were noted by FPM:

The actual depth to the LNAPL in the formation as noted in the test pit (13.5 feet below the top of the slab, approximate elevation of 0 feet relative to NAD 1988) is somewhat greater (about 1.5 to 2 feet) than indicated by the measurements in the closest nearby wells. Therefore, it appears that the depth to LNAPL as measured in the wells is somewhat inaccurate, as is typical of LNAPL measurements in wells. The actual depth to the LNAPL is likely to be greater than reported in the wells, perhaps by 1.5 to 2 feet. For planning purposes, it can be conservatively assumed that the actual depth to the LNAPL is about 1.5 feet greater than reported in the wells.

Boring logs throughout the LNAPL area indicate that LNAPL-impacted interval ranges from about 0.5 to 2 feet thick. The top of the LNAPL-impacted zone is generally found at about 13 to 15 feet below the top of the slab (except in immediate proximity to tanks), which when integrated with the varying slab elevations, results in the top of the LNAPL-impacted zone at about elevation 0 feet (consistent with the test pit). The bottom of the LNAPL-impacted zone was generally identified at about 14 to 17 feet below the top of the slab (generally between elevations -0.5 to -2 feet). The smear zone above

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the LNAPL can be assumed to be about one foot thick. The boring logs provide very consistent information, given the inherent nature of the boring process and the variability of subsurface materials beneath the Site.

Based on this information, we conclude that except in areas characterized by releases the interval impacted by LNAPL is likely to be present between an elevation of +1 and -2 feet in the LNAPL area. For purposes of remedial alternative evaluation, it will be assumed that the smear zone is approximately 1 foot-thick and the LNAPL interval is approximately 2 feet thick.

2.2.3 Underground Utility Survey

An underground utility survey and mark-out was performed by the Subsurface Utilities Division of BL Companies (BL), under contract to FPM, to obtain information for remedial measures assessment and planning. BL is a professional utility location and surveying firm with extensive experience in New York City. The survey was performed to delineate the locations, approximate depths, and construction of underground utilities present beneath the sidewalks and roads in proximity to and downgradient and crossgradient of the Site (the survey area). During the survey the locations of all identified utilities on the streets and sidewalks in the survey area were marked for future identification purposes and the topography of the survey area was recorded. In addition, the top of the casing of the accessible Site-related wells was surveyed so that a comprehensive set of well elevations was available for evaluation of groundwater and LNAPL level data. Sewer manholes were also accessed and the invert elevation of each associated sewer line was surveyed. The survey is shown on Figure 2.2.3.1 and a copy of the survey (BL Companies, October 26, 2015, updated March 18, 2016) is included in Appendix B.

FPM provided BL with an AutoCAD survey and utility location information previously obtained by others for use in developing the survey. A utility mark-out was conducted in the survey area, including identification of visible utility features, identification of known utilities in the Site building and the exterior surfaces of buildings in the survey area, surveying with an electromagnetic induction device, and surveying with a ground-penetrating radar device. Utility records were consulted during the markout, with the findings incorporated into the markout and survey. The markout/survey personnel were assisted with obtaining access to the Site building during this process. It should be noted that the markout did not include excavation to confirm utility depths or construction. This information was obtained, as feasible, via the utility records, field measurements, and markout procedures.

Following the markout, a utility and partial topographic survey was prepared by a NYC-licensed surveyor. This survey depicts the utility information obtained during the markout and utility records search, curbs, sidewalks, building faces, Site-related wells, and pipe inverts, sizes, and types, as feasible. It is noted that information concerning pipe inverts, sizes and types is limited due to the incomplete nature of the information provided in the utility company records, lack of access to fully-buried utilities, and the nature of the survey procedures. It should be noted that this survey was not performed for the purposes of establishing legal property lines or street lines.

The survey was reviewed together with previously-obtained survey information to evaluate the locations and depths of underground utilities present in the survey area, the estimated depths of utility backfill material (usually a granular material), and to compare this information with the elevation of the water table and the location and elevation of Site-related LNAPL. An assessment of the potential for utility backfill to provide a conduit for LNAPL migration or COVCs in groundwater was made. The following information was noted by FPM from these evaluations:

Page 2-12

Underground utilities present in the survey area include water supply (blue lines), natural gas (yellow lines), electric (red lines), sewer (combined sanitary and stormwater, green lines), fire protection (purple lines), and fiber optic (orange lines, limited to the southern part of Franklin Street).

Utilities are present beneath each of the streets in the survey area, with Franklin Street containing the greatest concentration of utilities. In some cases, multiple lines of the same type of utility are present beneath the streets. Utilities are also present beneath many of the sidewalks in the survey area, including gas and/or electric lines beneath the sidewalks on both sides of Franklin Street, gas, electric and/or sewer lines beneath the sidewalks adjoining the southwest and northwest corners of the Site, and electric and sewer lines beneath the sidewalks on either side of Commercial Street. In addition, utility service connections to properties are present in many locations beneath the streets and sidewalks. The locations of these utilities must be considered during evaluation of remedial measures that involve intrusive activities in the utility areas.

Utility elevation information obtained during this survey was limited to the electric manholes (top flange), sewer (top flange and inverts at manholes), fire protection manholes (top flange), and stormwater catch basins (top flange and invert). Of this information, only the sewer invert (bottom of pipe) information is necessary for assessing the potential for utility backfill to provide a conduit for LNAPL migration, as further discussed below. A limited amount of additional useful utility elevation information was obtained from a May 1946 contract drawing (City of New York Department of Public Works Bureau of Water Pollution Control, Contract No. 16, Sheet S-5), which depicts the depths of several utilities beneath Franklin and Dupont Streets to the southwest of the Site; a copy of this contract drawing is included in Appendix B. This contract drawing shows that the electric, gas, water, and fire protection lines located beneath the intersection of Franklin and Dupont Streets at that time were all located within approximately 5 feet of the ground surface, well above the depth of the water table and LNAPL. Although the water supply lines beneath Franklin Street and the eastern portion of Dupont Street have been replaced since this contract drawing was developed (NYCDEP Bureau of Water and Sewer Operations, Water Mapping, March 5, 2013, copy in Appendix B), it is most likely that the water lines would have been installed above the existing sewer line, as per typical construction practice. Because of the shallow depth of these utilities (above the groundwater surface), the backfill around these utilities is not a potential pathway for migration of contaminants associated with groundwater (including LNAPL). Construction activities that involve these utilities are also unlikely to involve potential contact with Site-related groundwater contamination or LNAPL.

The sewer invert elevations were reviewed and it was confirmed that the sewer lines slope downward to the north along Franklin Street and downward to the west along Dupont Street, with two lines intersecting just north of the of the Franklin Street/Dupont Street intersection. A sewer line also slopes downward to the west along Clay Street to intersect with the Franklin Street sewer. From the intersection of Clay, Commercial and Franklin Streets the sewer continues further to the northwest. Of note, there is no sewer mapped to the west of the Franklin Street/Dupont Street intersection and, therefore, no potential utility pathway for migration of groundwater contaminants or LNAPL was identified in this direction.

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2.2.3.1JB

ZS

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N

0 30 60 120

APPROXIMATE SCALE IN FEET

NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "EXISTING CONDITIONS SURVEY," ORIGINALSCALE 1" = 25'.

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The deepest sewer invert elevations near the Franklin/Dupont Street intersection are 3.8 and 3.5 feet (relative to the North American Vertical Datum of 1988, or NAVD88). Allowing for the New York City Department of Environmental Protection (NYCDEP)-required 0.5 feet of granular backfill material beneath the sewer pipe results in the bottom of the backfill material being at an estimated elevation of 3.0 to 3.3 feet in this area. Recent water level data from well MW-24, which is located closest to this intersection and the edge of the LNAPL, indicates that the water table in this well has fluctuated between elevations of 2.48 and 2.73 feet, which would not intersect with the sewer pipe backfill. Further to the east along Dupont Street the sewer invert is at 3.8 feet (bottom of backfill at 3.3 feet) and the water level in well MW-27, which is located near the edge of the LNAPL in this area, has varied between 2.52 and 2.79 feet, also below the sewer backfill. Groundwater elevation maps discussed in Section 2.2.4 below provide additional information concerning the depth to groundwater and further confirm that the water table is below the sewer backfill in these areas. This information indicates that LNAPL migration along the sewer alignment in Dupont Street or the sewers in the intersection of Dupont and Franklin Streets is not reasonably possible as the water table does not intersect the sewer line backfill in these areas.

Further north along Franklin Street, about halfway between Dupont and Clay Streets and near the northern limit of LNAPL beneath the street, the sewer invert is at 2.8 feet (bottom of backfill at 2.3 feet) and the water level in well MW-32, which is located near the edge of the LNAPL in this area, has varied between 2.37 and 2.67 feet. In this case, it is possible that the northern edge of the LNAPL could intersect the sewer backfill in this area. It is unlikely that any LNAPL migration could occur to the south as the sewer slopes upward in this direction, resulting in the backfill being above the water table. To the north, the sewer slopes downward into the water table, which may allow LNAPL migration in this direction if the sewer backfill is sufficiently permeable to provide a preferential migration pathway. It should be noted that LNAPL has never been observed in well MW-12, located near the north end of the sewer beneath Franklin Street, and LNAPL was not reported during recent construction activities involving the existing sewer connection at the intersection of Franklin and Commercial Streets. We conclude that any LNAPL migration to the north along the sewer alignment, if the LNAPL actually intersects the backfill, is likely to be limited and no indications of potential LNAPL have been noted along the sewer alignment.

The sewer invert under Clay Street in the area of the groundwater CVOC plume slopes downward to the west and ranges from elevation 3.2 feet above NAVD88 to the east of the CVOC plume to 2.0 feet above NAVD88 just to the west of the plume. Accounting for up to 0.5 feet of backfill below the sewer results in an elevation range of 2.7 to 1.5 feet above NAVD88 for the bottom of the sewer backfill. The elevation of the water table in this area has ranged between about 2.7 and 3.6 feet over the past year, based on data from wells MW-8 and MW-39, which are within the CVOC plume. Therefore, it is likely that groundwater containing CVOCs intersects the sewer backfill in this area. We note that CVOCs have not been detected in groundwater in excess of NYSDEC Standards at well MW-7, which is just west of the CVOC plume, nor does the configuration of the groundwater surface in this area suggest that any significant drawdown is occurring into the sewer backfill. In fact, the CVOC plume clearly crosses the sewer alignment, suggesting that groundwater flow is not at all influenced by the presence of the sewer.

2.2.4 Groundwater Flow Direction

Additional groundwater monitoring data obtained by FPM in 2015 during routine IRM activities and previously reported to the NYSDEC in the monthly monitoring reports were evaluated by FPM to obtain more

Page 2-15

comprehensive groundwater flow direction information. This evaluation was performed using well top of casing elevations surveyed by BL Companies during the course of the utility survey documented above and additional well casing survey information obtained following alteration of several wells in late October 2015. The survey information and water level data used during this evaluation are presented in Appendix B. Figures 2.2.4.1 and 2.2.4.2 present the groundwater flow direction information derived from the April and November 2015 water level measurements and represent the water table configuration during seasonal high groundwater conditions and seasonal low groundwater conditions, respectively.

It should be noted that FPM did not use data from wells containing LNAPL in this evaluation as the presence of LNAPL on the groundwater affects the depth of the groundwater surface. Although a correction can be applied to the groundwater level measurements based on the density and apparent thickness of the LNAPL, as discussed above the LNAPL apparent thickness measurements in the wells are generally greater (and sometimes significantly greater) than the actual LNAPL thicknesses in the formation due to capillary and other forces acting within the wells and the density of the LNAPL is likely to be somewhat variable, depending on the relative amounts of Hecla oil and phthalates. Because of the inaccuracy of the LNAPL apparent thickness measurements and density variability, use of the resulting data may lead to over-correction and/or inaccurate correction of the water level data. Therefore, to avoid these data evaluation issues only water level data from wells without LNAPL were used in this evaluation.

In addition, the water level data used in FPM’s analysis included data from wells with the same diameter to avoid potential variability that may be introduced by wells with different diameters. This resulted in the inclusion of water level data from all of the 2-inch diameter wells (without LNAPL) and the omission of water level data only from well RW-1, which is a 4-inch diameter well. Any potential effect on water level measurements due to capillary forces in the 2-inch wells is anticipated to be small.

The elevation of the water table in April 2015 (seasonal high water level) is shown on Figure 2.2.4.1 and indicates that groundwater flow beneath the Site and vicinity is generally to the southwest. The gradient (slope) is relatively low (about 0.004) on the northeastern portion of the Site and becomes nearly flat (about 0.001) on the southwestern portion of the Site and further to the southwest. This indicates that groundwater flow beneath the Site is very slow and likely decreases further to the southwest. Some variability was noted in the water levels, particularly to the southwest of the Site. This variability may be due to the nature of the materials in which the well screens are installed, as further discussed in Section 2.2.5 below. For the purpose of understanding the overall direction of groundwater flow in the Site vicinity, minor variations in water levels were ignored during development of Figures 2.2.4.1 and 2.2.4.2.

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WATER TABLE ELEVATIONSAPRIL 2015


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2.2.4.1JB

ZS

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JB

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0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "WATER TABLE ELEVATIONS - APRIL 2015,"DATED 1/12/16, ORIGINAL SCALE 1" = 60'.

LEGEND:

GROUNDWATER MONITORING WELL

WATER TABLE ELEVATION (FFET NAVD88)

PRODUCT RECOVERY WELL

IHWDS BOUNDARY

EXTENT OF LNAPL ON GROUNDWATER

WATER TABLE ELEVATION NOT CONTOUREDDUE TO WELL DIAMETER

WATER TABLE ELEVATION CONTOUR(DASHED WHERE INFERRED)

GROUNDWATER FLOW DIRECTION

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WATER TABLE ELEVATIONSNOVEMBER 2015


AUGUST 2016 12.0076485.00

FIGURE

2.2.4.2JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "WATER TABLE ELEVATIONS - NOVEMBER 2015,"DATED 1/12/16, ORIGINAL SCALE 1" = 60'.

LEGEND:


WATER TABLE ELEVATION (FFET NAVD88)


IHWDS BOUNDARY


WATER TABLE ELEVATION CONTOUR(DASHED WHERE INFERRED)

GROUNDWATER FLOW DIRECTION

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The elevation of the water table in November 2015 (seasonal low water level) is presented on Figure 2.2.4.2 and shows a similar west to southwest groundwater flow direction. The depth to groundwater was noted to be between 0.6 and 0.9 feet greater than in April 2015. The gradient on the northeastern portion of the Site (0.004) is about the same as during the seasonal high water level, is somewhat higher further to the east, and becomes nearly flat (slightly less than 0.001) to the southwest, also indicating very slow groundwater flow.

Synoptic groundwater and LNAPL (where applicable) elevation measurements are obtained monthly from nearly all of the Site wells during routine IRM activities and are available for use as needed to confirm the groundwater flow direction around the Site. Wells that are not part of the IRM program can be accessed as needed to obtain groundwater elevation readings. This information will be available for additional groundwater flow direction evaluation during remedial design.

2.2.5 Stratigraphic Cross-Sections

A general discussion of the Site stratigraphy was provided in the RI Report based on the borings performed during the RI and geotechnical borings performed in late 2014 in support of Site redevelopment. Additional analysis of the available stratigraphic data has been performed by FPM to more fully evaluate the stratigraphic framework beneath the Site and vicinity and assess potential relationships between the stratigraphy, the Site infrastructure, subsurface utilities, and the distribution of Site-related contaminants.

As noted in the RI Report, published information documents that the Site vicinity is generally underlain by unconsolidated fill that, in turn, overlies marsh and alluvial deposits, till, ground moraine, and other glacial deposits, and finally Paleozoic and Precambrian bedrock (USGS, 1999 and USGS, 1989), The shallow unconsolidated glacial deposits that cover much of western Long Island, including the Site vicinity, were deposited during the Wisconsian Glacial period and were associated with the southern¬most extent of the Laurentide Ice Sheet. The Site is located in an area dominated by a recessional moraine associated with the retreating Laurentide Ice Sheet. The resulting stratigraphy reflects depositional environments associated with the retreating glacier and includes:

Recessional moraine deposits caused by linear accumulation of till material formed during a hiatus in the retreat of a glacier. A published geologic map (Bennington, 2003) indicates that there are recessional moraines near the Site;

Silt and clay deposits associated with kettle ponds and glacial lakes; and

Fine to medium-grained sand deposits associated with deltas that form where lower-energy streams feed into kettle ponds or glacial lakes.

It is important to note that many depositional environments can occur within relatively short distances in proximity to receding glaciers. Therefore, it is typical for the resulting stratigraphy to be a complex mixture, both vertically and laterally, of various materials. This variability is evident in the stratigraphic framework underlying the Site and vicinity.

The available boring/monitoring well logs from the RI, the geotechnical investigation, and previous investigations performed by others (Advanced Site Restoration, LLC, March 2007) were reviewed together with

Page 2-19

the information obtained from the test pit (described above) to identify the significant stratigraphic layers present in the subsurface. These layers were then correlated to develop several stratigraphic cross-sections across the Site and into the surrounding vicinity. The cross-section locations are shown on Figure 2.2.5.1 and the cross-sections are depicted on Figures 2.2.5.2 through 2.2.5.6.

FPM noted that the quality and nature of the stratigraphic information shown on the boring/monitoring well logs is highly variable and, therefore, when interpreting stratigraphic relationships more emphasis was placed on information that appeared to be of higher quality (recent boring/well logs, geotechnical borings, test pit log) and less emphasis was placed on older information of apparent lower quality. In certain instances, discrepancies were noted between boring logs and other observations of the same materials; in these cases, the information sources were considered and the data were interpreted in a manner that placed more emphasis on consistent data and observations made at the time the work was performed. It should also be noted that the cross-sections do not depict each individual layer that may be identified on the more detailed boring logs, but were prepared to show that nature of more significant stratigraphic layers and their interpreted relationships.

Following cross-section development, the subsurface infrastructure beneath the Site (tanks), subsurface utility information from the utility survey, and the approximate configuration of the water table surface and LNAPL extent were added to the cross-sections by FPM so that potential relationships between these features and the stratigraphy could be discerned. ft should be noted that the depth of the water table surface and LNAPL are approximations as the depths of these fluids vary somewhat over time.

The significant stratigraphic layers identified by FPM include the following (from shallow to deep):

Fill — Found from beneath the overlying impervious material (building slabs, streets, sidewalks) to a maximum of about 8 feet below the on-site slab, the fill is a variable mixture of sand, silt, gravel, often containing anthropogenic debris. Fill (often termed "historic fill") is common in the New York City metro area, particularly in proximity to surface water bodies and other former low-lying areas, and appears to underlie the entire Site and vicinity with the possible exception of the Greenpoint Playground where anthropogenic debris was not evident.

Sand/Silt — An interval consisting of sand, silty sand and/or sandy silt underlies nearly all the Site and vicinity. This sand/silt interval appears to be missing beneath the southeastern portion of the Site and may also be missing to the southwest of the Site. Intervals of clay, silt, sand, and gravel were identified within the sand/silt, particularly in the lower portions of this interval, but do not appear to be continuous. This sand/silt interval may represent delta deposits associated with a glacial lake or larger kettle hole.

Clay (upper) — An interval of clay is found just below, and perhaps intercalated with, the sand/silt deposits on the southwest portion of the Site and extending off-site to the west and southwest. This clay interval may be associated with a former kettle hole.

Sand and Gravel — An interval of very loose sand and gravel with cobbles was observed in the test pit and is correlated with similar sand and gravel deposits identified in borings beneath primarily the eastern, southern and southwestern portions of the Site and extending off-site to the west and southwest. The approximate extent of the sand and gravel deposits is depicted on Figure 2.2.5.1. These deposits were noted to thicken to the west and southwest and were not fully penetrated by borings in these areas. This material appears to represent till deposits associated with a recessional moraine.

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2.2.5.1JB

ZS

ZS

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JB

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0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "CROSS-SECTION LOCATION MAP,"DATED 1/13/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY

TANK AREA

CROSS-SECTION

APPROXIMATE EXTENT OF SANDAND GRAVEL INTERVAL

SOIL BORING

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2.2.5.2JB

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JB

1" = 50'

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1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "W1-E1 CROSS-SECTION," DATED 1/13/16,ORIGINAL SCALE 1" = 50'.

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2.2.5.3JB

ZS

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MT

JB

1" = 50'

NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "W2-E2 CROSS-SECTION," DATED 1/13/16,ORIGINAL SCALE 1" = 50'.

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2.2.5.4JB

ZS

ZS

MT

JB

1" = 50'

NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "NE1-SW1 CROSS-SECTION," DATED 1/13/16,ORIGINAL SCALE 1" = 50'.

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2.2.5.5JB

ZS

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1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "NW-SE CROSS-SECTION," DATED 1/13/16,ORIGINAL SCALE 1" = 50'.

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2.2.5.6JB

ZS

ZS

MT

JB

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1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "SW2-NE2 CROSS-SECTION," DATED 1/13/16,ORIGINAL SCALE 1" = 50'.

Page 2-26

Clay (lower/ — A significant thickness of clay and silt is found below the sand and gravel interval (where present) throughout the Site and to the north and northwest. This clay was found to extend to bedrock (between about 48 and 62 feet bgs) in nearly all the geotechnical borings performed on the Site. The lower clay/silt interval may also be present to the west and southwest of the Site, but this was not confirmed as the borings in these areas did not fully penetrate the sand and gravel interval. Based on the extent and thickness of this clay and silt interval, it likely represents deposits associated with a glacial lake.

The estimated configurations of the USTs present beneath the Site building are shown on Figures 2.2.5.2 through 2.2.5.6. These configurations are based on the known locations of the USTs, their sizes, and their projected depths based on typical tank gauge charts. It appears that the USTs were installed through the fill and into the underlying native materials, including the sand/silt interval and the sand and gravel interval. None of the USTs appears to intercept the groundwater. There is a close association between the locations of the USTs that formerly contained phthalate or Hecla Oil and the current on-site location of LNAPL.

The groundwater surface, or water table, is found at a depth of approximately 10 to 15 feet beneath the Site. The generalized elevation of the water table is depicted on the stratigraphic cross-sections. Where the water table surface is within the sand and gravel interval it is noted to be relatively flat and where the water table is found within the sand/silt deposits or upper clay it appears to have a greater slope, consistent with the lower permeability of these materials. Although some finer-grained materials are present within the sand and gravel deposits, the likely higher permeability of these deposits, in comparison to the clay and sand/silt intervals, may facilitate groundwater migration in the areas where these deposits are present. The variable nature of the materials into which the well screens are installed likely affects the water levels in the wells, resulting in some variability in the measured elevation of the water table surface.

The LNAPL is found primarily within the sand and gravel deposits, although it is noted to extend laterally somewhat into the sand/silt deposits or upper clay. It was noted that the top of the sand and gravel interval is deeper to the west of the Site (beneath Greenpoint Playground and in the MW-24 area, Figures 2.2.5.3 and 2.2.5.4) and in these areas the water table surface extends into the upper clay that overlies the sand and gravel deposits. This upper clay, where it is present and intersects the water table, likely restricts groundwater and LNAPL movement. Further to the south (Figure 2.2.5.6) the bottom of the sand and gravel interval is found at a shallower depth and the interval is not laterally extensive. In this area, the water table is near the bottom of the sand and gravel and intersects the surrounding sand/silt interval. In this area groundwater and LNAPL movement are likely restricted by the lower-permeability sand/silt.

The locations and approximate depths of the surveyed utilities in the Site vicinity are depicted on the cross-sections shown in Figures 2.2.5.2 through 2.2.5.6 (a map view showing the utility locations was presented in Figure 2.2.3.1). It should be noted that these depictions include only the utility lines and do not reflect the backfilled utility trenches. The utilities in the Site vicinity (and their associated trench backfill) appear to be located above the water table in all cases, except for the sewer line beneath the northern portion of Franklin Street. At the location where the cross-section shown on Figure 2.2.5.3 intersects Franklin, Street, the sewer (including backfill) is estimated to be above the LNAPL. However, as discussed in Section 2.2.3, the sewer slopes downward to the north and it is possible that the northern edge of the LNAPL intersects the backfill beneath the sewer under the northern portion of Franklin Street.

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2.2.6 Waste Evaluations

FPM anticipated that contaminated Site media (LNAPL, groundwater, soil, and/or vapor) will be removed and disposed as waste during remedial activities. An assessment was performed of the nature (hazardous vs. non-hazardous) of those media that will generally require transport and disposal at permitted facilities (LNAPL, groundwater, soil). Additional testing of the LNAPL has also been performed by FPM to evaluate its PCB content.

For contaminated vapors, it is understood that these are generally treated (if necessary) at the point of generation (remedial system) and discharged to the atmosphere in compliance with NYSDEC Air Guide 1 criteria. In this case, the treatment media may require treatment and/or disposal. As this waste stream (treatment media) is anticipated to represent a relatively small portion of the overall waste streams that may result from Site-related remediation, its potential characterization is not further evaluated in this FS.

For the LNAPL, the NYSDEC has previously determined (Order on Consent R2-20110524-870) that the phthalate-containing LNAPL removed from the Site USTs during closure and the phthalate-containing LNAPL on the groundwater were considered to be hazardous waste as they were understood to contain the listed hazardous wastes diethylhexyl phthalate (U028) and/or di-n-octyl phthalate (U107). Based on this determination, for the purposes of this FS it is assumed that phthalate-containing LNAPL will be continued to be considered a listed hazardous waste; however, this determination is still being evaluated and will be further discussed in future design documents.

Under the NYSDEC's Technical Administrative Guidance Memorandum (TAGM) 3028 "Contained-In" Criteria for Environmental Media" environmental media (soil and groundwater) containing hazardous constituents from listed hazardous waste identified in 6 NYCRR Part 371 must be managed as hazardous wastes unless the media contain hazardous constituent concentrations that are at or below action level concentrations. This policy is applicable to soil and groundwater removed from their natural environmental pursuant to a NYSDEC-approved permit, order or work plan. The NYSDEC was contacted to confirm the necessary protocol and it is planned to obtain a "contained-in" determination from the NYSDEC following the procedures in TAGM 3028.

The "contained in" demonstration document will evaluate soil and groundwater data from the RI relative to the Groundwater Action Levels and Soil Action Levels in TAGM 3028 (8/26/97 version) for the listed hazardous wastes associated with the Site. This evaluation is anticipated to indicate that soil heavily contaminated by phthalates and generally found in the vicinity of the LNAPL plume would be classified as hazardous waste and that soil outside of this area would be determined to be non-hazardous waste, For the groundwater, although waste determinations are still being evaluated, for the purposes of this FS it is assumed that groundwater near the east side and beneath the LNAPL plume that contains phthalates may be classified as hazardous waste if it were removed and disposed as waste. It is anticipated that groundwater in other areas would be determined to be non-hazardous waste. The waste disposal evaluations included in Section 4 of this FS were developed using these assumptions; however, waste determinations are still being evaluated and will be further discussed in future design documents.

For the groundwater contaminated with CVOCs, it is noted that there is no record of chlorinated solvent storage, use, or disposal at the Site. Therefore, the CVOC-impacted groundwater is not associated with an identifiable listed hazardous waste. There is no basis for identifying this groundwater as a hazardous waste or for evaluating this groundwater under the "Contained-In" TAGM. This groundwater, if generated as a waste, would be tested for the criteria required by the potential disposal facility, with the results evaluated against

Page 2-28

the facility's disposal criteria. For the purposes of this FS, it is assumed that this groundwater is contaminated, may require treatment before disposal, and is classified as non-hazardous waste.

Contaminated groundwater recovered as part of the remedial system will be treated at the point of generation and discharged to the NYCDEP Sewer System in compliance with NYCDEP Waste Water Quality Control Application permits. In this case, the treatment media may require treatment and/or disposal. As this waste stream (treatment media) is anticipated to represent a relatively small portion of the overall waste streams that may result from Site-related remediation, its potential characterization is not further evaluated in this FS.

In August 2015, during routine screening of the waste LNAPL generated during IRM activities, PCBs were identified in the LNAPL. The levels of PCBs were low (LNAPL was classified as non-Toxic Substance Control Act (TSCA) regulated hazardous waste) and previously-obtained RI data did not indicate a potential PCB source at the Site. Additional LNAPL sampling was performed to evaluate the nature and extent of PCBs within the LNAPL.

LNAPL sampling was conducted on September 14, October 15, and November 12, 2015. The locations sampled in September included each of the three-intermediate bulk container (IBC) totes in which the removed LNAPL is contained on-site pending transport for disposal (one tote in use and two not in use) and wells MW-21, MW-22, MW-25 and RW-9. The locations sampled in October include wells MW-A, MW-5, MW-15, RW-2, RW-3, RW-10 and RW-12. Well RW-R was sampled in November. Sampling was conducted by FPM environmental professionals using standard techniques for LNAPL sampling from monitoring and recovery wells. The samples were containerized, labeled, and shipped via lab courier under chain of custody procedures to Alpha Analytical of Westborough, MA, which is a NYSDOH-Environmental Laboratory Accreditation Program (ELAP) certified lab. The laboratory reports from these sampling events are included in Appendix B and the results have been uploaded to the NYSDEC's Electronic Information Management System (EIMS).

The data from these three sampling events are presented on Table 2.2.6.1 and demonstrate the following:

PCBs were not detected in the residual LNAPL in the two IBC totes not in use at that time (C-1 and C-2), or in any of wells MW-A, MW-15, RW-10, MW-21, MW-22, MW-25, or RW-4;

The PCB Aroclor 1260 was detected at between 1.24 mg/kg (estimated) and 6.71 mg/kg in the LNAPL samples from the remaining sampled wells (note that PCBs in oil are reported on a per-weight basis; as the specific gravity of this LNAPL is very close to that of water, the mg/kg unit may reasonably be expressed as ppm); and

The PCB Aroclor 1260 was detected at 3.66 mg/kg in the LNAPL sample from the IBC tote that was in use to store LNAPL on-site (C-3) in September 2015.

Based on this information, it appears that PCBs may be present in a limited portion of the on-site LNAPL plume near the southwest side of the Site and in off-site LNAPL to the southwest along Franklin Street, as shown in Figure 2.2.6.1. Historic records indicate several spills of PCB-containing oils in Con Edison electric vaults and manholes on Dupont and Franklin Streets, which may have resulted in the PCB detections in the LNAPL. The detected concentrations of PCBs are low (no more than 6.71 ppm) and are well below the level (50 ppm or greater) that would trigger disposal as a TSCA-regulated waste. However, the affected LNAPL will require disposal as a waste with low-level PBC contamination. The testing provided sufficient information to allow for

Page 2-29

segregation of LNAPL containing PCBs from LNAPL that does not contain PCBs. LNAPL segregation was initiated during IRM activities in November 2015.

2.2.7 RCRA Closure

The Site has a hazardous waste generator EPA ID number (NYD001468354) and has been identified as a Large Quantity Generator. As such, it is subject to Resource Conservation and Recovery Act (RCRA) closure requirements under 6 NYCRR Part 371. RCRA closure is required for one room on the west of the Site situated within Block 2487, Lot 1 (shown on Figure 1.1.1) where recovered phthalate is handled and stored.

Page 2-30

TABLE 2.2.6.1 LNAPL PCB ANALYTICAL DATA

FORMER NUHART PLASTIC MANUFACTURING SITE, NYSDEC #224136 280 FRANKLIN STREET, BROOKLYN, NY

Sample No. MW-A MW-5 MW-15 MW-21 MW-22 MW-25 RW-2 RW-3 RW-4 RW-9 RW-10 RW-12 C-1 C-2 C-3

Sample Date 10/15/2015 9/14/2015 10/15/2015 11/12/2015 9/14/2015 10/15/2015 9/14/15

Polychlorinated Biphenyls in milligrams per kilogram

Aroclor 1260 ND 2.63 ND ND ND ND 2.46 6.71 ND 1.24 J ND 2.86 ND ND 3.66

Notes:

C = IBC totes

ND = Not detected

J = Estimated concentration above the Method Detection Limit (MDL) and below the Reporting Limit (RL).

This table was developed from previous investigations performed by FPM Group

SHEET NO.



www.gza.com


PROJ MGR:

DRAWN BY:


SCALE:


AERIAL EXTENT OF PCBs IN LNAPL


AUGUST 2016 12.0076485.00

FIGURE

2.2.6.1JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONIC FILEPROVIDED BY DUPONT STREET DEVELOPERS, LLC, ENTITLED"AREAL EXNTENT OF PCBs IN LNAPL," DATED 1/13/16,ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY


PCBs PRESENT

PCBs ABSENT

Page 3-1

3.0 REMEDIAL GOALS, REMEDIAL ACTION OBJECTIVES, GENERAL RESPONSE ACTIONS, REMEDIAL TECHNOLOGY SCREENING

3.1 REMEDIAL GOALS

Chemical-specific remediation goals are used to define the area and volume of impacted media to be addressed to meet the Remedial Action Objectives (RAOs) discussed in this section. These remediation goals are based on the evaluation of Standards, Criteria and Guidance (SCGs), which are standards and criteria that are generally applicable, consistently applied, and officially promulgated. SCGs incorporate both the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) concept of "applicable or relevant and appropriate requirements" (ARARs) and the EPA's "to be considered" category of non-enforceable criteria and guidance. These evaluations are used to determine contaminant levels that will not endanger human health or the environment.

The terms "Standards, Criteria, and Guidance" (SCGs) as defined by the NYSDEC encompass the terms "ARARs" and "criteria and guidelines". The term "ARARs" refers to a promulgated and legally enforceable rule or regulation. "Criteria and guidelines" refer to policy documents that are not promulgated and not legally enforceable. However, "criteria and guidelines" become enforceable if they are incorporated into an accepted Record of Decision (ROD) or other Decision Document. The NYSDEC term "SCGs" is used in this FS.

There are three types of SCGs that remedial actions may have to comply with:

Chemical-specific SCGs set concentrations for the chemicals of concern (e.g., SCOs established under 6NYCRR Subpart 375-6);

Location-specific SCGs may restrict remedial actions based on the characteristics of the site or its environs (remedial activities proposed for wetlands may be restricted by regulations protecting these areas); and

Action-specific SCGs may affect remediation activities based on the type of technology selected.

The following chemical-specific SCGs and guidelines have been identified for soil for this Site:

Federal Resource Conservation and Recovery Act (RCRA) regulations establish regulatory levels for various contaminants to be utilized in the evaluation of whether a solid waste is a hazardous waste;

6 NYCRR Part 371 — Identification and Listing of Hazardous Wastes provides guidance concerning the identification of hazardous waste;

TAGM 3028 — "Contained-In" Criteria for Environmental Media: Soil Action Levels provides guidance concerning the identification of hazardous waste; and

The NYSDEC Part 375 Environmental Remediation Program and the associated CP-51 Soil Cleanup Guidance Policy provide guidance (SCOs) concerning remediation levels for various contaminants present in sol.

Page 3-2

The following chemical-specific SCGs have been identified for groundwater at the Site:

NYSDEC Water Quality Regulations for Surface Waters and Groundwaters (6NYCRR Parts 700¬705, revised January 17, 2008), establish water quality standards for surface waters, groundwater, and effluent discharges.

The following chemical-specific guidelines have been identified for soil vapor/indoor air at the Site:

The NYSDOH Guidance Document for Evaluating Soil Vapor Intrusion in the State of New York (October 2006) provides guidance concerning remediation levels for various contaminants that may be present in indoor air and soil vapor; and

The NYSDEC's DAR-1 Guidelines for the Control of Toxic Ambient Air Contaminants establishes criteria used to evaluate air emissions that may be associated with remedial systems.

The following guidelines have been identified for LNAPL at the Site:

The NYSDEC Part 375 Environmental Remediation Program (6NYCRR 375-1.8(c)) provides guidance concerning source removal and control.

3.2 REMEDIAL ACTION OBJECTIVES

Remedial Action Objectives (RAOs) are media-specific goals for protecting human health and the environment. RAOs form the basis for this FS by providing overall remedial goals for addressing the Site-related contamination. The RAOs are considered during the identification of appropriate remedial technologies and formulation of alternatives. Documentation of the rationale employed in the selection of the RAOs is presented in the following sections.

The proposed remedial measures for this Site are intended to be consistent with, and an integral part of, the final remedy. The RAOs were selected from the NYSDEC's compilation of generic RAOs for public health protection and environmental protection based on the anticipated restricted residential and/or commercial use of the Site and on potential impacts to the surrounding community and environment as identified during the RI and discussed above. The selected RAOs are to mitigate, to the extent necessary and practical, the following:

Soil — Public Health Protection

Prevent ingestion/direct contact with soil contaminated with Site-related contaminants, including TCE and related chlorinated solvents in soil in the northeastern portion of the Site beneath the Site's existing building slab and in the immediate off-site area beneath the sidewalk, and LNAPL-related contaminants in the soil in and near areas where LNAPL is present; and

Prevent inhalation of or exposure from contaminants volatilizing from Site-related VOC contaminants in soil to the extent practicable.

Page 3-3

Soil — Environmental Protection

Prevent migration of contaminants from TCE-impacted soils in the northeastern portion of the Site that could result in groundwater and/or soil vapor contamination; and

Prevent migration of contaminants from LNAPL-impacted soils that could result in groundwater contamination to the extent practicable.

Groundwater Public Health Protection

Prevent ingestion of groundwater impacted by Site-related contaminants in excess of drinking water standards; and

Prevent contact with or inhalation of Site-related chlorinated VOCs from impacted groundwater. Groundwater — Environmental Protection

Restore groundwater to pre-release conditions to the extent practicable; and

Remove the source of groundwater contamination to the extent practicable.

Soil Vapor — Public Health Protection

Mitigate potential impacts to public health resulting from the potential for soil vapor intrusion from Site-related VOCs.

LNAPL

Remove the source of LNAPL contamination to the extent practicable.

RAOs were selected to address the protection of both human health and the environment, the anticipated performance of each remedial action will be evaluated relative to the RAOs to estimate the acceptability of public health and environmental impacts. Final remediation goals may differ from RAOs and will be established in the ROD for the Site.

For soils, the 6NYCRR Part 375 and CP-51 Soil Cleanup Objectives (SCOs) have been established as the RAOs. These SCOs are applicable to soil and were formulated to be protective of human health and the environment.

For groundwater, the NYSDEC Class GA Ambient Water Quality Standards established in the NYSDEC Water Quality Regulations for Surface Waters and Groundwaters (6NYCRR Parts 700-705, revised March 8, 1998) have been selected as the RAOs. It should be noted that these water quality standards were developed for fresh groundwater that has the potential to be utilized for water supply. As noted above, the sodium content of the groundwater in the Site vicinity is elevated due to natural conditions, precluding its use for water supply purposes without significant treatment (desalinization). Therefore, although the GA Standards are the selected RAOs, application of these RAOs is considered from a practical perspective in this FS.

Page 3-4

For sub-slab soil vapor, the guidance in the NYSDOH Guidance Document for Evaluating Soil Vapor Intrusion in the State of New York (October 2006) has been selected as the RAO. This guidance is used to establish no further action, monitoring, and mitigation levels for VOCs in indoor air and soil vapor.

For LNAPL, the NYSDEC Part 375 Environmental Remediation Program (6NYCRR 375-1.8(c)) for source removal and control has been selected as the hierarchy of source removal and control measures.

It should be recognized that although these RAOs have been identified, it may be technically and/or economically impractical to actively remediate the media of concern to the levels dictated by these RAOs. Because of the Site's location in a heavily-developed urban area, the location of the impacted materials beneath cover materials (building slab and/or pavement) and/or at depths where no human contact is reasonably anticipated with the use of appropriate controls, and the lack of use of the groundwater in proximity of the Site for water supply purposes, remediation to levels proscribed by the RAOs may not be practicable. Therefore, the implementation of engineering controls (ECs) and institutional controls (ICs) is anticipated for this Site to control potential exposures to residual impacts that are not remediated to the RAOs.

3.3 IDENTIFICATION OF GENERAL RESPONSE ACTIONS

Based on the information presented in Section 2, general response actions (GRAs) are identified to address the identified soil, groundwater, and soil vapor contamination associated with the Site for the protection of public health and the environment. GRAs describe classes of technologies that can be used to meet the remediation objectives for each medium of concern. GRAs are considered in this FS with the understanding that ECs and ICs are anticipated for this Site.

Soil impacted with SVOCs (phthalates) is present on-site and off-site at and near the groundwater interface in the area where LNAPL is present. Soil impacted by phthalates is also likely to be associated with some of the on-site USTs and piping systems formerly used to store and manage the phthalates and Hecla oil when the facility was operating. These soils are presently covered by the concrete building slab (on-site) and pavement (off-site) and do not present a current exposure hazard. There is the potential for exposure to these soils during sub-slab construction and/or remedial activities at the Site and during off-site intrusive activities that extend to the depth where these impacts are present. Accordingly, the GRAs to be considered for the SVOC- and LNAPL-impacted soil on-site and off-site are no action, in-situ treatment/containment, and excavation/disposal.

Soil impacted by several metals is present on-site and off-site. These metals detections are related to materials in the historic fill identified on-site and off-site and are characteristic of historic fill commonly found in the New York City metropolitan area. Neither the distribution of these detections nor the levels of the detections is indicative of a release of metals contaminants at the Site, and metals impacts do not contribute to groundwater or soil vapor impacts. Therefore, GRAs are not indicated for metals-impacted soil for remedial purposes. GRAs are indicated to control potential exposures to metals-impacted soil that may during ground-intrusive activities that disturb this soil. Therefore, the GRAs considered for remedial purposes that involve intrusive activities will include GRAs that address potential exposures to metals-impacted soil.

Page 3-5

Soil impacted by TCE and related chlorinated solvents is present in a limited solvent "hot spot" area in the northeastern portion of the Site. The impacts extend to off-site soil on the south side of Clay Street immediately to the north of the on-site area of TCE impact, but do not extend to north side of Clay Street, confirming that the area of chlorinated VOC-impacted off-site soil is limited. The impacted soil has been identified generally only at depth (10 feet bgs and deeper). These soils are presently covered by the concrete building slab (on-site) and pavement (off-site) and do not present a current exposure hazard. There is the potential for exposure to these soils during sub-slab construction and/or remedial activities at the Site and during off-site intrusive activities that extend to the depth where these impacts are present. As noted below, the VOC-impacted soil is the likely source for chlorinated solvent impacts to groundwater and soil vapor beneath the northeastern portion of the Site and extending off-site somewhat to the north-northwest. Accordingly, the GRAs to be considered for the VOC-impacted soil on-site and off-site are no action, in-situ treatment, and excavation/disposal.

LNAPL containing phthalates and Hecla oil is present floating on the groundwater surface beneath much of the western portion of the Site and extends off-site to the west and southwest, including beneath the east side of Franklin Street, the north side of Dupont Street, and across these streets somewhat to the northwest and southeast corners of the Franklin/Dupont intersection. LNAPL has also been found in one off-site well (MW-7) on the south side of Clay Street. LNAPL does not extend as far as the playground to the west of the Site, the vacant property to the southwest of the Site, or across Clay or Commercial Streets. The LNAPL is presently covered by the concrete building slab (on-site) and pavement (off-site) and does not present a current exposure hazard. LNAPL is not volatile or highly soluble and, therefore, does not contribute to soil vapor impacts and only minimally contributes to dissolved groundwater impacts. There is the potential for exposure to LNAPL during sub-slab construction and/or remedial activities at the Site and during off-site intrusive activities that extend to the depth where LNAPL is present. Although the available data indicate that the LNAPL is not mobile under current conditions, these conditions may change in the future due to activities such as dewatering or excavation conducted during on-site and/or off-site development and construction. Accordingly, the GRAs to be considered for the LNAPL on-site and off-site are no action, in-situ treatment, in-situ containment, excavation/disposal, and recovery/disposal.

Phthalates are present dissolved in groundwater generally located on the periphery of the area where LNAPL is present, including off-site wells to the east, south, and southwest of the Site. The phthalate DEHP was also detected in three wells located off-site to the northeast, in proximity to the off-site portion of the former NuHart facility. The groundwater is not used for drinking water (or any other purpose) in the Site vicinity and, therefore, the groundwater does not present a current or future concern for exposure except during intrusive activities that extend to the depth of the groundwater. The GRAs to be considered for the phthalate-impacted groundwater associated with the Site include no action, monitoring, and in-situ and ex-situ treatments.

TCE and related chlorinated VOCs associated with the Site are present dissolved in groundwater beneath the northeastern portion of the Site and extend a short distance off-site to the north-northwest. The groundwater is not used for drinking water (or any other purpose) in the Site vicinity and, therefore, the groundwater does not present a current or future concern for exposure except during intrusive activities that extend to the depth of the groundwater. VOC-impacted groundwater

Page 3-6

can contribute to soil vapor impacts. The GRAs to be considered for the VOC-impacted groundwater associated with the Site include no action, monitoring, and in-situ and ex-situ treatments.

Soil vapor impacted by TCE and related CVOCs is present beneath the northeastern portion of the Site building, with the greatest impacts coinciding with CVOC-impacted groundwater in this area. The impacts do not extend to the western or southern portions of the Site. CVOCs are present in off-site soil vapor in a limited area to the east and north of the Site. Site-related CVOC soil vapor impacts extend to the north, across Clay Street, but do not extend as far northward as the north side of Commercial Street. Direct contact and/or inhalation of soil vapor released from the subsurface during intrusive activities presents a potential exposure concern. Exposure to vapors in indoor air resulting from soil vapor intrusion also presents an exposure concern. The GRAs to be considered for sub-slab soil vapor at the Site and affected off-site areas include no action, monitoring, and mitigation.

In addition to technology-related GRAs, non-technology GRAs are identified for this Site, including ICs such as controls of on Site usage, groundwater usage, and off-site subsurface access, and ECs, including cover systems. These GRAs are included in the evaluation of remedial action alternatives, as described in the following sections.

3.4 IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES

Potential remedial technologies to address the Site-related impacts are identified in this section and are initially screened with respect to effectiveness and implementability. Recommendations are developed regarding retaining technologies for further consideration or rejecting technologies due to significant concerns. Remedial technologies that are retained for further evaluation are combined to form comprehensive remedial action alternatives, which are discussed in Section 4.

It should be noted that the screening of remedial technologies includes an assessment of implementability relative to existing and anticipated conditions at the Site and surrounding vicinity. These conditions include the following factors:

The Site is currently divided into multiple lots that are connected by one network of adjoining buildings throughout the Site. Based on the anticipated development, for this report, the lots will be referenced as three separate Sites which will be an agglomeration of existing lots identified by the New York City Department of Buildings as defined below. The below is currently an anticipated Site plan, and not considered final.

o The Lot 57 portion of the building was previously used as a warehouse and currently in the NYC Office of Environmental Remediation (OER) Voluntary Cleanup Program (NYC VCP). A remedial investigation (RI) and Remedial Action Work Plan (RAWP) were prepared by GZA. Both of documents are under the public review period.

o Lot 17 Site: A series of investigations on the Lots (17, 18, 20, and 21) of the NuHart factory building have identified environmental impacts that are currently being managed under NYS DEC authority within the Petroleum Spills program. Lot 17 is located in between Lot 57 and the Registry Site. It is anticipated that this Site will apply for the NYSDEC Brownfield Cleanup Program. A development plan has not been proposed for this Site.

Page 3-7

o The Registry Site is a planned future development consisting of Lots 1, 10, 12, 72, and 78. A

development plan has not been proposed for this Site.

The Registry Site (the Site) is anticipated to be redeveloped, but the redevelopment plan and schedule is not known. At present and for the near term, the Site building is not occupied or in use for any purpose. Future redevelopment is anticipated to include removal of the existing Site slab and the underlying soil to about 5 feet below the surrounding grade and construction of a crawlspace to grade. The first floor of the new building is anticipated to be used, at least in part, for parking. Following future redevelopment, it is anticipated that the Site will be used for restricted residential and/or commercial purposes;

The Site is in a highly-urbanized area with significant below-grade utility infrastructure in the public streets and sidewalks that adjoin the north, west and south sides of the Site. Subsurface access in the streets and sidewalks is controlled via a permit process;

The ground surface at the Site and surrounding area is fully covered by pavement or building slabs. The only significant unpaved surface near the Site is in the Greenpoint Playground, located to the west of the Site, across Franklin Street;

One property located to the southwest of the Site, across the Franklin Street/Dupont Street intersection, is anticipated to be redeveloped with a school building. The proposed configuration of this redevelopment is not known;

The NYSDEC has issued correspondence (March 17, 2015) indicating that an impermeable barrier to prevent migration onto downgradient properties not already impacted by LNAPL will be a required element of the final remedy to address the contamination at this Site. As noted in Section 2.2.1 above, testing results have demonstrated that the LNAPL is essentially immobile under current conditions and repeated observations from multiple wells over several years have not shown any migration of the LNAPL. However, the testing results have been interpreted differently by the NYSDEC. In addition, development activities may be conducted in the future near the LNAPL. To the extent that these activities alter current subsurface conditions near the LNAPL, they may trigger LNAPL migration. These activities could include dewatering that alters the water table surface in the vicinity of the LNAPL, removal of fine-grained soils that may block LNAPL migration, or other activities that alter the subsurface in a manner that increases the potential for LNAPL migration; and

The Site area is served by the public water supply and no private water supply wells are reported to exist in the vicinity of the Site. As noted above, the sodium content of the groundwater, which appears to be a natural condition related to the Site's location in proximity to surface water bodies, precludes use of the groundwater for potable water purposes unless desalinization is performed. We note that the proposed RAOs for groundwater for this Site are to restore groundwater to pre-release conditions to the extent practicable and to remove the source of groundwater contamination. Furthermore, Part 375-1.8(d)(iii) states that all remedies shall, to the extent feasible, prevent the further migration of groundwater plumes. Evaluation of groundwater remediation technologies takes into consideration the RAOs, feasible prevention of further plume migration, and the natural quality of the groundwater.

Page 3-8

Potential remedial technologies that may be used to address impacted soil, groundwater and soil vapor for LNAPL associated with the Site are identified in Tables 3.4.1 through 3.4.4, respectively, at the end of this section. Each technology was evaluated in terms of two threshold criteria: a) overall protectiveness of public health and the environment and b) conformance with SCGs.

The criteria "overall protectiveness of public health and the environment" includes an evaluation of how each alternative would eliminate, reduce or control through removal, treatment, containment, engineering controls (ECs) or institutional controls (ICs) any existing or potential human exposures or environmental impacts identified by the RI. It also evaluates the ability of each alternative to achieve each of the RAOs and draws on the assessments of the other evaluation criteria, especially long-term effectiveness and permanence, short-term effectiveness, and compliance with SCGs.

Conformance with SCGs was evaluated by assessing whether application of the remedial technology is likely to result in achieving the SCGs identified in Section 3.1. The SCGs are identified and the ability of the remedy to achieve the SCGs is assessed. This assessment considers whether the remedial technology may be part of a complete remedial program, whether conformity to the SCGs may result in greater risk to public health or the environment, whether conformity to the SCGs may be technically impractical from a scientific or engineering perspective, and whether the program will attain a level of performance that is equivalent to the SCGs using another method or approach.

After the preliminary screening, the retained technologies were combined to form remedial action alternatives, which are discussed in Section 4 and screened against the following balancing criteria: long-term effectiveness and permanence, reduction of toxicity, mobility or volume of contamination, short-term impact and effectiveness, implementability, cost-effectiveness, and land use. The remedial action alternatives also include consideration of ICs and ECs.

Community acceptance is also evaluated during the remedial selection process after public review of the potential remedies and as part of the selection and approval of a remedy for the Site. Community acceptance will be evaluated during the public comment period.

Page 3-9

TABLE 3.4.1 SCREENING OF SOIL REMEDIAL TECHNOLOGIES

FORMER NUHART PLASTIC MANUFACTURING SITE #224136 BROOKLYN, NEW YORK

Technology Overall Protectiveness of

Public Health and the Environment

Conformance with SCGs Recommended Action

SCGs for Soil:

•Federal Resource Conservation and Recovery Act (RCRA regulations establish regulatory levels for hazardous waste •6 NYCRR Part 371 provides guidance concerning identification of hazardous waste . TAGM 3028 ("Contained-In" Criteria for Environmental Media) provides guidance concerning identification of hazardous waste •NYSDEC's Part 375 Environmental Remediation Program and CP-51 Soil Cleanup Guidance Policy provide guidance (SCOs) concerning remediation levels for soil contaminants

No Action Not protective as there is no active reduction in contaminant concentrations and no ECs or ICs to prevent exposures.

Does not result in conformance with SCGs.

Reject due to non-compliance with threshold criteria.

In-situ Treatment of VOCs (TCE) by Soil

Vapor Extraction (SVE)

Protective as it will directly reduce VOC concentrations in soil in the treatment area, and remove source of soil vapor and groundwater impacts.

Can result in achievement of SCGs, although it may be difficult to achieve SCGs in tight soils.

Retain for further consideration due to protectiveness and ability to achieve SCGs. Design must consider soil types.

In-situ Treatment of VOCs (TCE) by

Chemical Oxidation

Somewhat protective as it can directly reduce VOC concentrations in soil in contact areas, thus reducing the source of soil vapor and groundwater impacts. Protectiveness is limited by soil contact issues and application quantities. Highly oxidizing treatment chemicals may cause elevated subsurface temperatures and pose a public health risk.

Can result in limited achievement of SCGs in soil in contact areas. Difficult to apply effectively in unsaturated zone and/or tight soils.

Reject due to limited compliance with threshold criteria, and application difficulties, effectiveness limitations, and safety risk.

In-situ Thermal Treatment (TCE)

- Electrical

Resistivity Heating (ERH)

Protective for VOCs in soil as it directly reduces VOC concentrations in soil, thereby removing source of soil vapor and groundwater impacts. However, will cause high soil vapor VOC concentrations, resulting in additional impacts to soil vapor.

Can achieve SCGs in soil, although with a potential risk to public health and the environment. Difficult to apply ERH safely in occupied and/or populated spaces due to potential electrical exposure issues. ERH causes elevated subsurface temperatures, resulting in additional safety concerns and potential damage to subsurface utilities. Application of ERH precludes other remedial activities while ERH is ongoing.

Retain for further consideration if Thermal Conductive Heating is not viable.

This table was developed from previous submissions performed by FPM Group

Page 3-10

TABLE 3.4.1 (CONTINUED) SCREENING OF SOIL REMEDIAL TECHNOLOGIES




Conformance with SCGs

Recommended Action

In-Situ Thermal Treatment (TCE)

- Thermal Conduction Treatment

Protective for VOCs in soil as it indirectly reduces VOC concentrations in soil (including tight soils), thereby removing source of soil vapor and groundwater impacts. However, will cause high soil vapor VOC concentrations, resulting in additional soil vapor impacts.

Can achieve SCGs in soil, including tight soils, if properly designed with closely-spaced wells. Somewhat elevated subsurface temperatures result - subsurface utilities may require monitoring.

Retain due to protectiveness and ability to achieve SCGs in tight soils. Design must consider soil types, removal of resulting soil vapors, and subsurface temperatures.

Excavation with Off-site

Disposal (TCE and phthalates)

Protective for VOCs and phthalates in soil as it directly reduces phthalate and VOC concentrations in soil, thereby reducing sources of soil vapor and groundwater impacts.

Full conformance with SCGs via excavation is technically impractical as much of the impacted soil is found at depth and some is off-site beneath roadways, sidewalks, and/or utilities. However, conformance with SCGs can be achieved in excavation areas.

Retain due to protectiveness and ability to achieve SCG conformance in excavation areas.


Page 3-11

TABLE 3.4.2 SCREENING OF GROUNDWATER REMEDIAL TECHNOLOGIES FORMER NUHART PLASTIC MANUFACTURING SITE #224136

BROOKLYN, NEW YORK

Technology Overall Protectiveness of Public Health and the Environment Conformance with SCGs Recommended

Action SCGs for

Groundwater: •NYSDEC Water Quality Regulations 6NYCRR Parts 700-705 establish water quality

standards for surface waters, groundwater, and effluent discharges.

No Action Not protective as there is no active reduction in contaminant concentrations and no ECs or ICs to prevent exposures.



Groundwater Monitoring (TCE and

phthalates)

Not protective as there is no active reduction in contaminant concentrations. However, monitoring data will be needed to assess changes in contaminant concentrations due to other remedial measures and to evaluate the nature and extent of groundwater impacts.

Does not result in conformance with SCGs, but does provide the data to assess whether conformance with SCGs has been achieved by other remedial measures.

Retain for inclusion as an aspect of other remedial measures.

In-Situ Chemical Treatment

(TCE)

Can be protective in that VOC concentrations can be reduced in groundwater, but may not fully remediate groundwater impacts, depending on aquifer conditions and ability to fully contact affected aquifer.

Can result in conformance with SCGs within the treatment area, but additional investigation needed for remedial design. Performs best as a "polishing" treatment. Safety concerns with application of some chemical treatment materials.

Retain for further consideration. Design must include detailed assessment of VOC distribution in groundwater and safety concerns.

In-Situ Treatment - Air Sparging (TCE)

Protective in that elevated VOC concentrations can be reduced in groundwater in the treatment area. Will cause high soil vapor VOC concentrations, resulting in additional soil vapor impacts. Must be used with SVE to remove soil vapors.

Can result in conformance with SCGs in the treatment area, but can exacerbate VOCs in soil vapor unless used with SVE.

Retain for further consideration. Design must include SVE in the treatment area.

In-Situ Control - Physical Barrier

System (TCE and phthalates)

Provides limited protection in that further migration of dissolved contaminants may be controlled but there would be no reduction of contaminant concentrations.

Does not provide for conformance with SCGs except for outside of the barrier system but may assist with containing LNAPL for recovery with thermal treatment.


Ex-Situ Treatment -

Groundwater Pump-and-

Treat (TCE and phthalates)

Provides some protection in that further migration of dissolved contaminants may be controlled and elevated VOC and SVOC concentrations may be reduced.

Does not provide for conformance with SCGs as it is less effective for low VOC/SVOC concentrations.

Reject due to non- conformance with threshold criteria.


Page 3-12

TABLE 3.4.3

SCREENING OF SOIL VAPOR REMEDIAL TECHNOLOGIES FORMER NUHART PLASTIC MANUFACTURING SITE #224136

BROOKLYN, NEW YORK




SCGs for Soil Vapor:

•The NYSDOH Guidance Document for Evaluating Soil Vapor Intrusion in the State of New York provides guidance concerning remediation levels for VOCs in indoor air and soil vapor •The NYSDEC's DAR-1 Guidelines for the Control of Toxic Ambient Air Contaminants establishes criteria for air emissions from remedial systems.

No Action Not protective as there is

no active reduction in VOCs in soil vapor and no ECs or ICs to prevent exposures.


Reject due to non-compliance with threshold criteria,

Monitoring

Not protective as there is no active reduction in VOC concentrations. However, monitoring data will be needed to assess changes in VOCs in soil vapor due to other remedial measures and to evaluate the potential for SVI.

Does not result in conformance with SCGs, but does provide the data to assess whether conformance with SCGs in soil vapor has been achieved due to other remedial measures and whether remedial system air emissions are in conformance with SCGs.


Soil Vapor Extraction

Protective - SVE will reduce elevated soil vapor VOC concentrations in the treatment area, reduce the potential for SVI, and reduce the vapor source in soil.

Can achieve conformance with SCGs in soil vapor and VOC- impacted source soil. Monitoring is required to document SVE emissions conformance with SCGs.

Retain for further consideration. Design must include monitoring.

Mitigation — Vapor Barrier

Protective of public health in that it will reduce the potential for SVI. Not ' protective of the environment as soil vapor VOCs will not be reduced.

Provides for conformance with SCGs for indoor air. Does not provide for conformance with SCGs in soil vapor,

Retain for further consideration due to protection from SVI and ability to achieve SCGs for indoor air.

Mitigation - Sub- Slab

Depressurization (SSDS)

Protective of public health and the environment in that it will reduce the potential for SVI and reduce soil vapor VOCs.

Provides for conformance with SCGs for indoor air and may provide for conformance with SCGs in soil vapor if vapor sources are controlled or eliminated. Monitoring required to document SSDS emissions conformance with SCGs.

Retain for further consideration.


Page 3-13

TABLE 3.4.4 SCREENING OF LNAPL REMEDIAL TECHNOLOGIES


Technology Overall Protectiveness of Public Health and the Environment Conformance with SCGs Recommended

Action

SCGs for LNAPL:

•The NYSDEC Part 375 Environmental Remediation Program (6NYCRR 375-1.8(c)) provides guidance concerning source removal and control

No Action Not protective as there is no control or removal of source material and no ECs or ICs to prevent exposures.



Monitoring Not protective as there is no control or removal of LNAPL. However, monitoring data will be needed to assess changes in LNAPL due to other remedial measures.

Does not result in conformance with SCGs, but does provide the data to assess whether conformance with SCGs has been achieved due to other remedial measures.


Barrier - Physical

Provides some protection in that potential migration of LNAPL may be controlled but there would be no removal of LNAPL. Protection is permanent.

Results in partial conformance with SCGs in that potential LNAPL migration would be permanently controlled, but the source would not be removed.

Retain for further consideration, particularly in combination with LNAPL removal measures.

Barrier — Hydraulic

Provides some protection in that some LNAPL removal is likely and potential further migration of LNAPL may be controlled. However, this method will induce some LNAPL migration as a result of significant drawdown from groundwater pumping and no control or removal is provided if the active equipment fails.

Results in partial conformance with SCGs in that potential LNAPL migration would be controlled and some of the source would be removed while the equipment operates. Will not provide conformance with SCGs if equipment fails.

Reject due to partial compliance with threshold criteria and potential risks.

In-situ Thermal Treatment

- Electrical Resistivity

Heating (ERH)

Protective of public health and the environment in that LNAPL is removed from the subsurface in a dual phase extraction. Removal is limited by access issues and depth and can result in significant surface disruptions.

Provides for significant conformance with SCGs in the areas where LNAPL is accessible to removal via vapor and liquid extraction. Will remove source material from areas where heaters can be installed.

Retain for further consideration, particularly in combination with other measures and due to ability to achieve significant conformance in accessible areas.


Page 3-14

TABLE 3.4.4 (CONTINUED) SCREENING OF LNAPL REMEDIAL TECHNOLOGIES





In-situ Thermal

Treatment

- Thermal Conduction Treatment

Protective of public health and the environment in that LNAPL is removed from the subsurface in a dual phase extraction. Removal is limited by access issues and depth and can result in significant surface disruptions.

Provides for significant conformance with SCGs in the areas where LNAPL is accessible to removal via vapor and liquid extraction. Will remove source material from areas where heaters can be installed.

Retain for further consideration, particularly in combination with other measures and due to ability to achieve significant conformance in accessible areas.

In-situ Chemical Treatment

- Surfactant or

other Injection

May provide limited protection in that source control and removal may be improved if LNAPL viscosity is lowered. Bench Testing and pilot testing required to demonstrate protectiveness.

May provide limited conformance with SCGs if LNAPL recovery is enhanced. Typically used as a "polishing" method in combination with other remedial measures.

Retain for further consideration, particularly in combination with other measures. Bench and pilot testing are required to demonstrate effectiveness.

In-situ Stabilization

May provide limited environmental protection (source control) by reducing soil porosity/permeability. Does not provide any protection via a source removal mechanism. Bench testing would be required to evaluate feasibility and to assess treated material properties. Pilot testing required to assess field performance issues.

May provide limited conformance with SCGs via source control, but does not result in source removal. Requires closely-spaced application points, difficult to control injections in variable stratigraphy, and presents concerns for subsurface utilities. Subsurface obstructions may complicate implementation and reduce effectiveness.

Retain for further consideration particularly in combination with other measures. Bench and pilot testing are required to demonstrate effectiveness.

Extraction and Disposal

Protective of public health and the environment in that LNAPL is removed from the subsurface. Removal and transport of LNAPL in off-site areas presents potential safety concerns and must be properly managed.

Provides for significant conformance with SCGs in that source materials are controlled and removed. Removal may be enhanced by application of complementary technologies if supported by testing results. Monitoring is required to assess SCG conformance. Removal amounts are significantly affected by LNAPL properties and remedial design

Retain for further consideration due to conformance with threshold criteria.

Excavation with Off-site

Disposal

Protective of public health and the environment in that LNAPL is removed from the subsurface. Removal is limited by access issues and depth and can result in significant surface disruptions.

Provides for significant conformance with SCGs in the areas where LNAPL is accessible to removal via excavation. Does not provide for source control and does not result in source removal in inaccessible areas.

Retain for further consideration due to ability to achieve significant conformance in accessible areas.


Page 4-1

4.0 REMEDIAL ACTION ALTERNATIVES

4.1 EVALUATION OF REMEDIAL ACTION ALTERNATIVES

Remedial action alternatives appropriate to address impacts for the affected media at the Site were formulated by combining the retained technologies screened in Section 3.4 with ICs and/or ECs, as appropriate, to develop comprehensive remedial actions. In general, the retained remedial technologies for soil include in-situ soil vapor extraction or SVE (for VOCs), thermal conductive heating for (VOCs) and excavation with off-site disposal (for VOCs and phthalates). The retained remedial technologies for groundwater include groundwater monitoring (in support of other remedial technologies for VOCs and phthalates), in-situ chemical treatment (for VOCs), and in-situ treatment by air sparging or AS (for VOCs). The retained remedial technologies for sub-slab soil vapor include monitoring (in support of other remedial measures), remediation by SVE, mitigation by vapor barrier installation, and mitigation using sub-slab depressurization. The retained remedial technologies for LNAPL include LNAPL recovery (off site)), TCH to enhance the recovery of LNAPL on-site, monitoring (in support of other remedial measures), cutoff wall and physical barrier, extraction and disposal, excavation with off-site disposal, in-situ stabilization (subject to verification testing), and chemical treatment (in combination with other measures). In general, the ICs considered include restrictions on Site usage, restriction of groundwater usage, implementation of a Site Management Plan (SMP) to provide for management of ongoing remedial activities and residual impacts, implementation of an environmental easement for the Site, and implementation of an off-site access control. The ECs considered include maintenance of a cover system over residual impacted materials, and implementation and operation of remedial systems.

The retained remedial technologies for each of the media have been combined into comprehensive remedial alternatives that address all media. The comprehensive alternatives include alternatives that address the identified impacts for the Site and provide protection for potential exposures, and an alternative that is intended to achieve a full cleanup of the Site to pre-release conditions to the extent practicable.

Each of the comprehensive remedial actions considered is evaluated against nine criteria, including:

Threshold Criteria

1. Overall protection of public health and the environment;

2. Compliance with SCGs;

Primary Balancing Criteria

3. Long-term effectiveness and permanence;

Page 4-2

4. Reduction of toxicity, mobility, or volume;

5. Short-term impacts and effectiveness;

6. Implementability;

7. Cost-effectiveness; and

8. Land use.

Modifying Criteria

9. Community impact

Due to the location of the Site, the extent of the contamination, the nature of the remedial approaches and the community participation, a ninth criterion has been added into the evaluation criteria with consideration of each remedial action impact to the community during on-site remedial construction. Community impact was broken down into categories including traffic, noise, air quality and aesthetics. It should be noted that this is a generalized list based on knowledge and experience in the New York City Metropolitan area. The off-site remedy will have impacts to all the categories listed above, each alternative consists of the same off-site remedial approach, there will be no difference between the evaluation criteria for each remedy, therefore it has not been included. Community acceptance will also be evaluated during the remedial selection process after public review of the potential remedies and as part of the selection and approval of a remedy for the Site. Community acceptance will be evaluated during the public comment period.

4.1.1 Alternative 1 - No Action Alternative

In accordance with the standard regulatory criteria, a No Action remedial alternative was screened against the threshold criteria, as described in Section 3.4 and was rejected as it would not be protective of public health and the environment or result in conformance with SCGs. This alternative was not further evaluated against the balancing criteria and is not considered further herein.

4.1.2 Alternative 2 - Air Sparging/Soil Vapor Extraction, Off-site Physical Barrier, LNAPL Extraction/Disposal, Groundwater/ LNAPL Monitoring, Soil Vapor/SVI Monitoring, Limited On-site Removals, and ECs/ICs

This comprehensive remedial alternative presented and evaluated by FPM would address identified impacts in each of the Site media, provide for monitoring of changes in contaminant levels, and implement protective measures to control potential exposures. This alternative assumes that the current Site condition (vacant building) continues during the beginning of remedy implementation and that redevelopment includes removal of the existing Site slab and the underlying soil to about 5 feet

Page 4-3

below the surrounding grade and construction of a crawlspace to grade, with parking above the crawlspace.

Although it is assumed that the top 5 feet of Site soil will be removed for redevelopment purposes under all the Alternatives, for the purposes of this FS, soil removal for construction (other than the targeted removal of soil contaminated with LNAPL or VOCs) is not considered to be a remedial activity. It is assumed that all soil removal for remedial or construction purposes will be conducted under the Site Management Plan (SMP) that would be an IC for this Site, as discussed below. Soil removal under the SMP would include screening by an environmental professional and appropriate management, including removal and disposal. Although this soil will include historic fill that would likely be disposed as non-hazardous waste, for this purposes of this FS the costs associated with soil removal for construction purposes are not included in this FS.

Air Sparging/Soil Vapor Extraction

Air sparging (AS) and soil vapor extraction (SVE) would directly address groundwater VOC impacts identified on the northeastern portion of the Site and in the downgradient vicinity of the Site. This alternative would actively reduce VOC concentrations in the affected areas by enhancing volatilization of VOCs from the groundwater. An SVE system would be used in the AS areas to remove the volatilized VOCs from the subsurface and directly reduce soil vapor impacts. Groundwater and soil vapor monitoring would be required to document the progress of remediation. It is anticipated that this remedial method would be implemented prior to construction.

This alternative would actively reduce VOC concentrations in the affected soils by enhancing volatilization of VOCs, which would be captured by the SVE system, removed from the subsurface, and discharged to the atmosphere. Effluent monitoring would be performed to evaluate the reduction in VOC concentrations over time and to confirm that emissions from the SVE system meet regulatory requirements. The NYSDEC DAR-1 guidance document would be used to determine if effluent treatment is necessary. SVE will reduce the amount of VOCs in Site soil that have the potential to migrate to groundwater or soil vapor and would also directly remove soil vapors in the system's radius of influence (ROI), thus providing soil vapor intrusion (SVI) mitigation in the system area.

A site plan showing the potential layout of an AS/SVE system is presented in Figure 4.1.2.1. The AS portion of the system would be designed to treat areas where significant groundwater VOC contamination has been observed on-site and in close downgradient and cross gradient proximity to the on-site VOC source area. The AS system would likely include four AS wells located on-site near the source area, two of which would be positioned to treat groundwater beneath the sidewalk immediately north of this area. The AS screens would be set at a depth of approximately 18 to 20 feet to treat groundwater situated in the more permeable stratigraphic intervals above the extensive clay/silt that underlies the area. Based on previous experience with other AS systems in the NYC metro area, it is anticipated that an airflow of between 10 and 16 standard cubic feet per minute (SCFM) per well at a pressure of 20 to 40 pounds per square inch would be needed to result in an ROI of about 30 feet at each AS well. A compressor capable of a total flow of 60 to 80 SCFM at the targeted pressure is indicated.

SVE wells would be required to capture vapors resulting from sparging. The SVE wells would also treat VOC-impacted soil that may be present in the unsaturated zone in the presumed source area and remove soil vapors associated with the VOC-impacted area. SVE system design would take stratigraphic variations into consideration to maximize effectiveness. The SVE system would likely include three wells;

Page 4-4

TABLE 4.1.2.1 ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2

AIR SPARGING/SOIL VAPOR EXTRACTION

Description Cost (30 Years) Cost (4 Years)

Capital Costs

AS/SVE System Installation $108,000 $108,000

Engineering Design Costs (15%) $16,200 $16,200

Contingency (15%) $16,200 $16,200

Oversight and Management (25%) $27,000 $27,000

Reporting (15%) $16,200 $16,200

Capital Cost Subtotal $183,600 $183,600

Annual Operation, Monitoring, and Maintenance Costs $58,400 $58,400

OM&M Net Present Worth $1,179,400 $223,700

AS/SVE System Removal $10,100 $21,800

TOTAL COST (Capital and OM&M Net Present Worth) $1,373,100 $429,100


Notes: Assumed interest rate is 5% and assumed inflation rate is 2%. All costs rounded to the nearest $100

SHEET NO.



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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 2 AS/SVE SYSTEM LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.2.1JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 2 AS/SVE SYSTEM LAYOUT,"DATED 3/17/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY

TCE >100 ug/L IN GROUNDWATER

PROPOSED AIR SPARGE WELLWITH RADIUS OF INFLUENCE

PROPOSED SOIL VAPOR EXTRACTION WELLWITH RADIUS OF INFLUENCE

Page 4-6

potential SVE well locations are shown on Figure 4.1.2.1 and are based on previous experience with SVE system layouts in the NYC metro area. It is anticipated that an SVE ROI of about 50 feet may be achieved with a flow rate of about 100 SCFM under a vacuum of between 10 and 150 inches of water. The blower would be appropriately sized for the anticipated total flow rate and vacuum of the SVE system. Sub-slab monitoring points would also be installed to just below the slab to allow for confirmation of the SVE ROl and to allow for sub-slab vapor sampling, as needed.

Costs for an AS/SVE system to treat the VOC source area have been estimated as shown on Table 4.1.2.1. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for both a 30-year remedial period and a four-year remedial period. Based on previous experience with AS/SVE systems, the AS/SVE system is anticipated to reach the limits of its effectiveness within about four years of operation.

Off-site Physical Barrier

An off-site physical barrier, such as a sheet-pile wall is considered as part of Remedial Alternative 2 to prevent potential LNAPL migration onto the downgradient property that is planned to be developed with a school. Although LNAPL has not been identified in any of the monitoring locations adjoining this property, it is possible that LNAPL migration could be triggered by future construction activities such as dewatering that alter subsurface conditions. Therefore, to prevent potential future exposure and reduce the potential impact to the environment, a physical barrier is considered. Monitoring will be necessary to assess the potential presence of LNAPL near the physical barrier and is discussed in a subsequent section of this report. If LNAPL does migrate to the vicinity of the physical barrier, then LNAPL extraction and disposal.

would be required to remove the LNAPL in proximity to the barrier. LNAPL extraction and disposal are discussed in the following section.

The location of the contemplated physical barrier (just to the southwest of the Franklin Street/Dupont Street intersection) is shown on Figure 4.1.2,2; potential LNAPL extraction locations in proximity to the barrier are also shown on this figure, should LNAPL recovery become necessary.

Subsurface physical barriers may be constructed by various means, including installation of interlocking steel sheets (sheet piles), excavation of a trench that is backfilled with a low-permeability material (such as bentonite) to form a barrier wall, and injection/mixing of low-permeability materials in overlapping boreholes (deep soil mixing/grouting) to form a grout curtain. Of these methods, barrier walls and grout curtains have generally presented more installation concerns and are less reliable in preventing migration, particularly in situations with significant infrastructure and/or stratigraphic variability, such as the Site vicinity. Interlocking sheet piles are generally more reliable in preventing migration and are in very common use in urban settings. Therefore, a sheetpile physical barrier is considered in this remedial alternative.

Interlocking sheet piles would be installed along the physical barrier alignment to an estimated depth of approximately 20 feet, which would place the bottom of the physical barrier between approximately 9 and 10 feet below the water table surface. For the purposes of this FS it is assumed that the barrier would be constructed within the sidewalk area outside of the potential school property, although the barrier alignment details would be determined during remedial design, considering the proximity of utilities and other infrastructure to the alignment. It will be necessary to remove portions of the sidewalk

SHEET NO.



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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 2 OFFSITE PHYSICAL BARRIERAND LNAPL EXTRACTION LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.2.2JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 2 OFFSITE PHYSICAL BARRIERAND LNAPL EXTRACTION LAYOUT," DATED 3/17/16,ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY


PROPOSED PRODUCT RECOVERY WELL

POTENTIAL PRODUCT RECOVERY WELL

PROPOSED PHYSICAL BARRIER

Page 4-8

TABLE 4.1.2.2

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 OFF-SITE LNAPL PHYSICAL BARRIER

Description Cost

Capital Costs:

Off-site Physical Barrier — School Site $256,800

Engineering Design Costs (15%) $38,500

Contingency (15%) $38,500

Oversight and Management (25%) $64,200

Reporting (15%) $38,500

TOTAL COST: $436,500


Note: All costs rounded to the nearest $100.

Page 4-9

and underlying soil along the alignment to allow for sheet pile placement and the sidewalk would be restored following construction. Monitoring wells removed during construction would also be replaced.

The costs for physical barrier construction have been estimated as shown on Table 4.1.2.2. Backup for these costs is provided in Appendix C.

LNAPL Extraction/Disposal

LNAPL extraction of the phthalates and disposal is considered as part of Remedial Alternative 2 to reduce the amount of LNAPL in the environment over time. Monitoring will be necessary to document the anticipated reduction in LNAPL and confirm changes in the LNAPL extent and apparent thickness over time; monitoring is discussed in the following section.

LNAPL extraction may be accomplished using recovery wells and/or recovery trenches. Recovery trenches would be excavated through the LNAPL and into the underlying groundwater and backfilled with a highly permeable material, such as gravel, to allow for LNAPL flow into and through the trench. LNAPL recovery sumps are placed at appropriate locations in the trench and each sump is equipped with LNAPL recovery equipment. Trenches can provide good LNAPL recovery but can be difficult to install properly in areas with significant subsurface infrastructure. Recovery wells consist of wells installed through the LNAPL area and into the underlying groundwater to a depth sufficient to allow for variations in the depth of the LNAPL over time and to provide sufficient room for the recovery equipment. Each well must be spaced appropriately and properly sized for the recovery equipment, with the well screen and gravel pack properly sized for the surrounding soils. Recovery wells generally must be closely spaced to provide for good LNAPL recovery, but are generally more easily installed than trenches in areas with subsurface infrastructure. Recovery equipment in either trenches or wells may consist of manually operated equipment (if LNAPL recovery is slow) or installed powered equipment (if LNAPL recovery is more rapid).

The selection of recovery trenches or wells for each remedial area should be made following a full assessment of the implementation considerations at each location. For the purposes of evaluating this remedial alternative, it is assumed that closely-spaced recovery wells are used for LNAPL recovery. Similarly, recovery equipment selection should be based on the characteristics and behavior of the LNAPL at each recovery location. For the purposes of evaluating this remedial alternative it is assumed that the recovery equipment may include belt skimmers or other high viscosity liquid pumps due to the viscosity of the LNAPL to be recovered.

LNAPL extraction is considered for several general areas, as shown on previously-presented Figure 4.1.2.2. An on-site extraction area is considered for most of the western and southern borders of the Site in the area where LNAPL is present adjoining these Site boundaries. Extraction of LNAPL along these Site borders will limit the potential for further migration of LNAPL from the Site and remove some LNAPL from beneath the off-site areas immediately adjoining the Site.

LNAPL extraction is also considered for the off-site area adjoining the western and southern borders of the Site where LNAPL is present, as shown on Figure 4.1.2.2. Extraction and disposal of LNAPL from this area is considered to remove LNAPL from beneath the sidewalk and at least a portion of the adjoining streets.

Page 4-10

An extraction area is also considered for an off-site location just to the southwest of the Franklin Street/Dupont Street intersection as a conservative measure. Although LNAPL has not been detected in any of the three existing monitoring wells located to the southwest of this intersection, the southwestern edge of the LNAPL plume (shown on Figure 4.1.2.2) is near this area and a physical barrier would be installed under this alternative as a protective measure. Potential LNAPL extraction wells would be installed and observed under the monitoring program (see below); LNAPL extraction would be implemented if LNAPL is detected in any of these wells in the future.

LNAPL has been identified beneath the southeastern and northwestern corners of the Franklin Street/Dupont Street intersection. Extraction and disposal of LNAPL from these locations is considered to remove LNAPL from beneath the sidewalk, at least portions of the adjoining streets, and in proximity to the off-site properties in this area. Proposed LNAPL recovery well locations are shown on Figure 4.1.2.2.

Costs for LNAPL recovery wells have been estimated as shown on Table 4.1.2.3. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for a 30-year remedial period and a 10-year remedial period. Based on previous experience with LNAPL recovery systems with the highly viscous nature of the LNAPL at this Site, LNAPL recovery rates will decline over time and it is anticipated that the system designed for current conditions may reach the limits of its effectiveness within 10 years of operation. Thereafter, LNAPL recovery methods may require modification for continued effectiveness and/or further LNAPL recovery may become impractical.

Groundwater/LNAPL Monitoring

Groundwater and LNAPL monitoring is considered as part of Remedial Alternative 2 to indirectly address the identified groundwater impacts and to confirm that the impacts continue to be limited to the proximity of the Site. LNAPL would also be monitored to document the anticipated reduction in LNAPL extent and apparent thickness over time. This alternative would not actively reduce groundwater contaminant concentrations or LNAPL, but would provide for assessment of the anticipated reduction in groundwater impacts and LNAPL extent and apparent thickness over time due to other factors, such as remediation of other affected media and ongoing natural processes.

Groundwater and LNAPL monitoring would be conducted at select wells downgradient, cross gradient, and upgradient of the Site. Figure 4.1.2.3 shows the proposed locations of groundwater monitoring wells (blue circles) and LNAPL monitoring wells (green circles) to be included in the monitoring networks. For reference, the locations of the LNAPL plume, the area of TCE-impacted groundwater, and proposed LNAPL recovery wells are also depicted on Figure 4.1.2.3. All the monitoring wells presently exist except for one well that would be needed on-site near the east end of the line of proposed on-site LNAPL recovery wells. Groundwater monitoring for most of the wells would be conducted semiannually (twice per year) for VOCs and SVOCs and groundwater monitoring around the AS/SVE system (MW-3, MW-8, MW-10, MW-13, MW-18, MW-34, MW-35, MW-39 and MW-40) would be conducted quarterly for VOCs to assess the progress of remediation. LNAPL monitoring would be conducted monthly. The monitoring frequencies would remain unchanged until the NYSDEC approves a change in monitoring frequency. Costs for groundwater/LNAPL monitoring have been estimated as shown on Table 4.1.2.4 and are presented on a projected net present worth basis over 30 years and over variable durations coordinated with the

Page 4-11

TABLE 4.1.2.3

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 2 LNAPL EXTRACTION/DISPOSAL


Capital Costs:

On-site Extraction Wells $99,900 $99,900


Contingency (15%) $15,000 $15,000


Reporting (15%) $15,000 $15,000

Capital Cost Subtotal (on-site): $169,900 $169,900

Off-site Extraction Wells $597,600 $597,600


Contingency (15%) $89,600 $89,600


Reporting (15%) $89,600 $89,600

Capital Cost Subtotal (off-site): $1,016,000 $1,016,000

Total Capital Costs: $1,185,900 $1,185,900

Annual Operation, Monitoring and Maintenance Costs: $139,200 $139,200

OM&M Net Present Worth $2,809,200 $1,222,600

Extraction Systems Removal $150,000 $271,000

TOTAL COST (Capital and OM&M Net Present Worth): $4,145,100 $2,679,500


Note:

All costs rounded to the nearest $100.

SHEET NO.



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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 2 GROUNDWATER/LNAPLMONITORING NETWORK LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.2.3JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 2 GROUNDWATER/LNAPLMONITORING NETWORK LAYOUT," DATED 3/21/16,ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY




PROPOSED GROUNDWATER MONITORING WELL NETWORK


PROPOSED LNAPL MONITORING WELL NETWORK

Page 4-13


GROUNDWATER/LNAPL MONITORING

Description Cost (30 Years) Cost (6 and 12 Years)

Capital Costs:

Monitoring Network Installation $6,300 $6,300

Contingency (15%) $900 $900


Reporting (15%) $900 $900

Total Capital Cost: $9,700 $9,700

Annual GW Monitoring and Reporting Costs: $81,300 $81,300

Annual LNAPL Monitoring and Reporting Costs: $77,600 $77,600


Monitoring Network Abandonment $19,500 $33.200




Page 4-14

potential duration of remedial systems operations. Backup for the estimated costs for this alternative are included in Appendix C.

Soil Vapor/SVI Monitoring

Monitoring for soil vapors and potential SVI is considered as part of Remedial Alternative 2 to assess soil vapor conditions over time and confirm that soil vapor impacts present beneath the concrete slab of the Site and pavement/sidewalks of nearby off-site areas do not affect indoor air quality at occupied structures. Soil vapor monitoring results would also be used to assess the progress of soil vapor remediation associated with SVE operation. This alternative would not actively reduce VOC concentrations in the soil vapor, but would be used to evaluate potential exposure issues, to assess reductions in VOC concentrations in soil vapor that may result from remedial measures, and to serve as a trigger for implementing SVI mitigation measures should the need arise.

Soil vapor monitoring would include installation of vapor implants through the Site building slab and through nearby sidewalks at several key locations to allow for monitoring of soil vapors over time. Monitoring locations would be selected to provide monitoring data at the same locations as previously to allow for data comparisons over time and to include additional locations to the south and west of the vapor source area. SVI monitoring would also include installation of vapor implants through the slabs of key off-site buildings (15 and 19 Clay Street) to allow for monitoring of sub-slab soil vapors and indoor air to be conducted periodically.

SVI monitoring would require that building access for implant installation and sampling be obtained from the property owners and that access for indoor air sampling be obtained from building occupants. For the purposes of this FS it is assumed that access to off-site properties is obtained. Figure 4.1.2.4 shows the proposed locations of soil vapor monitoring points. SVI monitoring points would be selected in consultation with off-site property owners.

Soil vapor and SVI monitoring are anticipated to be conducted at a frequency of twice per year (once during the heating season and once during the cooling season). During each monitoring event, co-located sub-slab soil vapor and indoor air samples, and an ambient air sample would be collected for laboratory analysis. All procedures and data evaluation would be in accordance with NYSDOH guidance. Monitoring would continue until the NYSDEC approves monitoring termination.

Costs for soil vapor and SVI monitoring have been estimated as shown on Table 4.1.2.5 and are presented on a projected net present worth basis over 30 years and over a six-year period as soil vapor conditions are anticipated to improve after the source soil is remediated. A monitoring frequency of twice per year is assumed. Backup for the estimated costs are included in Appendix C.

Limited On-site Soil and Tank Removal

Limited removal of on-site source infrastructure and associated soil would directly address some of the soil impacts associated with the presumed LNAPL source areas on the Site and indirectly address the LNAPL plume and dissolved SVOC groundwater impacts found on-site and in proximity to the Site by removing the infrastructure associated with the sources of these impacts. The removals under this alternative consist of the USTs and piping trench systems formerly used to store and convey phthalates

SHEET NO.



www.gza.com


PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 2 SOIL VAPOR/SVEMONITORING LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.2.4JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 2 SOIL VAPOR/SVE MONITORINGLAYOUT," DATED 3/17/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY

TCE IN SOIL VAPOR (ug/M³)

PROPOSED SOIL VAPOR MONITORING POINT


Page 4-16


SOIL VAPOR/SVI MONITORING


Capital Costs:


Contingency (15%) $4,100 $4,100

Design (15%) $4,100 $4,100


Reporting (15%) $4,100 $4,100


Annual Monitoring and Reporting Costs: $45,700 $45,700

OM&M Net Present Worth $921,704 $254,800

Monitoring Network Abandonment $15,871 $32,300

TOTAL COST (Capital and OM&M Net Present Worth): $983,675 $333,200



Page 4-17

and Hecla oil during the former plastic manufacturing process and the impacted soils that directly overlie or underlie these structures. The removals would be limited in that soil removal would be conducted to one foot below the depth of the construction excavation. This depth will allow for placement of clean backfill above the remaining impacted soil to allow for construction. This remedial method would be implemented during Site redevelopment, which is anticipated to include partial excavation of the Site subsurface.

This alternative would actively reduce soil contaminant concentrations by removing the source infrastructure and some source soil from the Site subsurface. Confirmatory (end-point) sampling would be conducted to document the condition of the remaining soil and assess if residual soil (exceeding applicable SCOs) remains present.

The locations of the limited removals are partially shown on Figure 4.1.2.5 and encompass the closed-in-place USTs and the piping trench systems (not shown on the figure) formerly used to store and convey phthalates and Hecla oil. Impacted soils overlying and underlying these features would also be removed down to one foot below the depth of the construction excavation.

Soil removal would include screening by an environmental professional to identify the impacted soil to be addressed under this remedial alternative. For the purpose of this FS it is estimated that volume of targeted impacted soil to be removed is about 1,000 cubic yards (not including the volume of the closed USTs). As the targeted soil consists primarily of LNAPL-saturated soil, it is assumed that it would require disposal as hazardous waste.

Although odors did not present a concern during the test pit activities described in Section 2.2.2 of this FS, the removal work may be conducted once the on-site building had been removed. Based on this, t is possible that odor control may be necessary during removal of the source infrastructure and associated soils, particularly if these activities are undertaken during warm weather and/or large excavations can remain open. A decision on whether to remove the buildings prior to remediation has not been made yet. Measures to monitor and, if necessary, control odors will be implemented during excavation activities. The control measures will include limiting the size of open excavations (particularly those excavations that include LNAPL-impacted soil), use of odor-control foam on odorous excavation surfaces and excavated materials as needed, covering stockpiles and loaded trucks with tight-fitting covers, limiting stockpile sizes, and promptly loading and transporting removed materials.

Confirmatory sampling for SVOCs would be conducted in the floor of each UST and piping trench excavation to evaluate the nature of impacts that may remain present after the limited removals. Any UST removals extending below the depth of construction would require backfilling and compaction below the level of the redevelopment excavation.

Costs for the limited removal alternative have been estimated as shown on Table 4.1.2.6. Backup for these costs are provided in Appendix C. Please note that these costs include capital costs for the limited removals only. Costs for additional measures (ECs and ICs) that may be needed to address residual soil contamination are addressed below.

SHEET NO.



www.gza.com


PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 2 LIMITED ONSITE REMOVALS


AUGUST 2016 12.0076485.00

FIGURE

4.1.2.5JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 2 LIMITED ONSITE REMOVALS,"DATED 3/23/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY


REMOVAL AREAS

Page 4-19


LIMITED ON-SITE SOIL AND TANKS REMOVAL

Description Cost

Capital Costs:

Remove/Dispose/Confirmatory Sampling $567,000


Engineering Design (15%) $85,100


Reporting (15%) $85,100




Page 4-20

Implementation of ECs and ICs

Implementation of ECs and ICs would be used to control potential exposures to impacts for all media under Remedial Alternative 2. Specifically, soil impacts will remain present on-site and LNAPL will remain present on-site and off-site. Soil vapor and groundwater impacts will also remain present, but are anticipated to diminish over time. ECs and ICs considered include a cover system EC (existing and future concrete slabs for the Site and existing sidewalks and road pavement for off-site areas) to provide protection from impacted soil and LNAPL, and ICs (Site and groundwater usage restrictions, and an SMP) to control Site use and potential on-site exposures to soil, soil vapor, LNAPL, and/or groundwater.

Access to the off-site subsurface is presently controlled by an IC consisting of a street-opening permit process that is required for penetration of the existing EC (sidewalks/pavement). An additional IC will be necessary to control potential exposures during off-site subsurface activities that are conducted to depths where Site-related LNAPL and associated impacted soil are present. The IC considered under this alternative is posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present.

Implementation and control of on-site ECs and ICs would be governed by an environmental easement for the Site. Implementation and control of off-site ECs and ICs would be governed by the existing street-opening permit process and an environmental notice.

Costs for the ICs and ECs, including implementation of an environmental easement, SMP, annual inspections and cover system repairs, certification, and reporting, have been estimated as shown on Table 4.1.2.7 on a net present worth basis over an assumed 30-year monitoring period. Backup for the estimated costs for this alternative are included in Appendix C.

Comprehensive Remedial Alternative 2 was evaluated relative to thenine criteria as follows:

Threshold Criteria

Overall protection of public health and the environment: This alternative actively addresses groundwater, soil, and soil vapor VOC impacts within the AS/SVE system ROI, and is anticipated to indirectly reduce soil vapor impacts outside of the SVE ROI and groundwater VOC impacts outside and downgradient of the AS ROI. Therefore, this alternative is considered protective of public health and the environment in that contaminants in groundwater, soil, and soil vapor will be reduced. This alternative is also protective of public health and the environment in that LNAPL (source material) will be controlled and reduced, which will also reduce the source of phthalate impacts to soil and groundwater. This alternative also provides a means of assessing the anticipated reduction of contaminant concentrations in soil, groundwater, and soil vapor, evaluating the extent and apparent thickness of LNAPL over time, and assessing potential exposures to soil vapor via SVI. This alternative does not actively reduce contaminant concentrations in soil vapor outside of the SVE ROI; however, it provides a means of evaluating and preventing potential human exposures and triggering SVI mitigation measures if necessary and, therefore, is protective of public health. Potential public exposures to residual impacted materials would be controlled and monitored via ECs and ICs. This alternative is more protective

Page 4-21


IMPLEMENT ECS AND ICS

Description Cost (30 Years)

Capital Costs:

Implement ECs and ICs $40,000


Total Capital Cost: $46,000

Annual Monitoring and Certification Costs: $12,700

Monitoring and Certification Net Present Worth $255,400

TOTAL COST (Capital and Mon./Cert. Net Present Worth): $301,400



http://cert.net/

Page 4-22

than Alternative 1 (No Action), but less protective than Alternatives 3, 4 or, 5, as described below;

Compliance with SCGs: This alternative provides for compliance with SCGs for VOCs in soil, groundwater and soil vapor in the VOC treatment area as VOC concentrations are anticipated to be reduced to near or below the SCGs in and downgradient of the AS/SVE treatment area. This alternative provides for partial compliance with SCGs relative to the LNAPL as LNAPL removal will occur, potential LNAPL migration onto an off-site property will be prevented, and the extent and apparent thickness are anticipated to be reduced over time. This alternative does not directly provide for compliance with groundwater or soil SCGs for other constituents (SVOCs), but it does reduce the SVOC source and provide a means for evaluating achievement of SCGs in groundwater due to remediation by other measures and ongoing attenuation processes. This alternative does not directly provide for compliance with SCGs in soil vapor except within the SVE ROI, but it does provide a means for assessing achievement of SCGs in soil vapor that may result from soil and groundwater remediation by AS/SVE, and for evaluating compliance with the SCGs for indoor air in occupied buildings. This alternative includes ECs and ICs to monitor and control potential exposures for those media where SCGs are not obtained, thereby assuring that the SCGs are not exceeded at potential exposure points;

Balancing Criteria

Long-term effectiveness and permanence: The VOC contaminants in the groundwater, soil, and soil vapor within the AS/SVE ROls would be actively and permanently reduced by this alternative, resulting in an effective and permanent long-term remedy for VOCs in this area. This alternative includes removal and off-site disposal of LNAPL from both on-site and off-site areas over time, thus permanently reducing the amount of LNAPL in the subsurface. The infrastructure from which the LNAPL was sourced will also be permanently removed under this alternative. Potential migration of LNAPL onto the off-site property to the southwest of the Site will also be permanently prevented. Groundwater/LNAPL monitoring does not provide a long-term effective or permanent remedy for groundwater impacts or LNAPL, but it provides a means to document changes in groundwater quality and LNAPL extent and apparent thickness due to other remedial measures and attenuation processes. Soil vapor and SVI monitoring do not actively remedy soil vapor impacts and, therefore, do not result in a long-term effective or permanent remedy for soil vapor. However, soil vapor and SVI monitoring do provide a means for documenting changes in soil vapor conditions and the potential for SVI due to other remedial measures and are a long-term effective means for assessing soil vapor conditions and the potential for SVI. Implementation of ECs and ICs will result in an effective long-term remedy from the standpoint of public health as the residual materials would be isolated from public contact by a cover, prohibition of groundwater usage, controls on Site usage, controls on off-site subsurface access, and an SMP to govern management of residual materials. Periodic inspection and certification would be required, resulting in an effective and permanent long-term remedy;

Reduction of toxicity, mobility, or volume: This alternative provides for a reduction of toxicity, mobility and volume of VOC contaminants in the groundwater, soil, and soil vapor within the

Page 4-23

AS/SVE ROls. This alternative also provides for some reduction of toxicity, mobility and volume of LNAPL. It does not directly provide for a reduction of the toxicity, mobility, or volume of other groundwater contaminants, but it does reduce the source of groundwater SVOC contaminants via LNAPL removal, and it provides a means for evaluating reductions in other groundwater contaminants due to other remedial measures or attenuation processes. This alternative does not directly reduce the toxicity, mobility, or volume of soil vapor contaminants except within the SVE ROl, but it does provide a means to evaluate reductions in soil vapor contaminants due to other remedial measures. The mobility of soil vapor contaminants would be reduced via maintaining a cover EC using ICs;

Short-term impacts and effectiveness: The short-term adverse environmental impacts or human exposures would be minimal to moderate during activities associated with implementing the AS/SVE remedial system, installing the off-site physical barrier and LNAPL recovery systems, groundwater/LNAPL monitoring, soil vapor and SVI monitoring, removals, and ECs/ICs. Some of the intrusive activities would be conducted after the existing Site building has been removed, which may result in some short-term impacts for which mitigation would be implemented. Some intrusive activities would also take place in the off-site sidewalk areas. An approved Health and Safety Plan (HASP) and Community Air Monitoring Plan (CAMP) would be required for the remedial construction and monitoring work and personal protective equipment (PPE) would be utilized by remedial workers to control exposures. CAMP monitoring results would be used to verify that short-term impacts are minimized and to trigger implementation of additional controls if needed. The surrounding community and remedial workers would generally be at little risk since there would be no contact with the affected media during the remedial and monitoring processes and road/sidewalk closures and Site security fencing would be used to restrict public access to the work areas. It should be noted that the LNAPL remedial and monitoring processes will include both on-site and off-site operations, including vehicle and remedial worker activities and LNAPL transfer and transport activities through the surrounding community during the period of LNAPL removal. These activities will be conducted under a HASP and CAMP designed to address potential safety and community concerns with these activities, but there will be an increase in vehicle traffic and LNAPL handling in the public street area. Potential exposures to VOC emissions will be monitored via SVE system effluent sampling and emissions controls will be used if necessary to ensure that emissions meet Air Guide 1 requirements. Short-term adverse environmental impacts or human exposures are not anticipated in association with implementing ECs and ICs. Following completion of remedial construction and associated cover repairs, there are not anticipated to be any human exposures as the affected media will be covered and the cover would be monitored;

Implementability: There are no significant technical limitations to implementing this alternative since readily-available AS/SVE remedial and monitoring technologies would be utilized, sheet pile installation is commonly performed, a majority of the proposed monitoring network is already present, there is no groundwater usage, the Site building is vacant and redevelopment is planned but not imminent, and groundwater, LNAPL, and soil vapor/SVI monitoring procedures have already been conducted under the NYSDEC-approved work plans. Design of the AS and SVE systems will need to take stratigraphic variations into account and phys ical barrier design will take into consideration the locations of utilities and other subsurface

Page 4-24

infrastructure. Design and construction of the LNAPL recovery systems will likely include some technical limitations due to the urban nature of the Site and vicinity and the presence of a significant amount of subsurface utilities. However, the selection of wells for the LNAPL recovery system is anticipated to reduce potential technical limitations. Implementation of the limited removals may be complicated by odor control or infrastructure issues. An SMP and an environmental easement would be required, both of which may be readily implemented. The existing street-opening permit process is anticipated to facilitate implementation of the off-site IC, which is anticipated to be posting of an environmental notice for street-opening permits in the Site vicinity. This alternative can be implemented within a reasonable time period, anticipated to be several months to a year;

Cost-effectiveness: This alternative provides long-term and short-term effectiveness and results in significant reductions in toxicity, mobility, and volume for VOCs in groundwater, soil and soil vapor within the AS/SVE system's ROls. This system is also likely to indirectly reduce groundwater and soil vapor impacts outside of the ROI, although it does not directly result in significant reductions in toxicity, mobility, and volume for groundwater or soil vapor contaminants outside of the ROI. This alternative also provides moderate long-term and short-term effectiveness for LNAPL control and reduction, including reductions in toxicity, mobility, and volume. Remedial system design, installation, operation, and monitoring costs are anticipated to be moderate, and the groundwater, LNAPL, soil vapor, and SVI monitoring design and implementation costs are low. Therefore, the costs for this comprehensive alternative are low to moderate, proportionally, relative to its overall effectiveness. The cost-effectiveness for the AS/SVE, LNAPL control and recovery, and monitoring components are increased when used in conjunction with the ECs/ICs that control potential exposures;

Land use: This alternative is somewhat protective of the current and reasonably-anticipated land use of the Site, which is presently vacant and anticipated to be redeveloped with a restricted residential and/or commercial use, as soil, groundwater and soil vapor impacted by VOCs within the AS/SVE system ROI would be remediated, mitigation of potential on-site SVI concerns would occur but may not be complete at the time the Site is redeveloped, LNAPL will be reduced, groundwater use is not occurring or contemplated, a cover will remain present or be reinstalled over impacted materials, and monitoring data would be available to assess LNAPL changes, groundwater quality, and potential SVI concerns on-site. This alternative is also protective of the current and reasonably-anticipated land use in the Site vicinity, as the AS/SVE system is anticipated to significantly reduce off-site soil, groundwater and soil vapor impacts, thereby mitigating potential SVI concerns, LNAPL will be reduced, potential LNAPL migration onto the off-site property to be developed with a school will be prevented, groundwater use is not occurring, a cover will remain present over impacted materials, and monitoring data would be available to assess changes in the condition of subsurface media over time. Under this alternative, materials exceeding applicable SCGs would be isolated from the public via cover, controls on land use, and controls on groundwater use. These controls would be implemented on-site via an environmental easement and an SMP and off-site via the existing street-opening permit process and posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present;

Page 4-25

Modifying Criteria

Community Impact: The on-site remedy consists of installation of a LNAPL Recovery System, AS/SVE System and limited Site removals. This remedy will not require the demolition of the existing building covering the Registry Site for remedial construction.

Traffic: This alternative is not anticipated to significantly impact traffic during this timeframe. Most of the traffic increases will stem from material deliveries and employees travelling to and from the Site. During the limited on-site removals, there will be an increase in truck traffic as waste truckers will be utilized to remove soil from the Site. The anticipated waste stream for this material would be a combination of urban fill and hazardous waste which will be transported by a combination of triaxles and long haul trailers, respectively. The trucking during this portion is set for localized excavation areas and is not anticipated to have a long-term impact on traffic patterns.

Noise: This alternative will utilize heavy construction vehicles to install the LNAPL extraction wells, AS/SVE wells and limited on-site removals. Remedial construction elements will provide a short-term impact on noise levels during installation and operation. The elements of this remedy can be installed, operated and/or performed within the existing building footprint which would greatly reduce noise impacts. It is assumed that Site development would be planned around the system whereas eventually the equipment would be installed within the building structure.

Air Quality/Odors: This alternative is not anticipated to significantly impact air quality. It is noted that during the remedy, community air monitoring will be performed during al l intrusive activities. All extracted vapors from the AS/SVE system will be treated to adhere to NYSDEC standards prior to discharge. Due to the short time frame of the installation of the remedial components, exhaust from the heavy machinery is not anticipated to be significant.

Aesthetics: This remedy allows for the on-site element of the remedy to be performed with or without the current building in place. No significant changes to aesthetics are anticipated on-site.

The total estimated costs for Remedial Alternative 2 are shown on Table 4.1.2.8.

Page 4-26

TABLE 4.1.2.8 ESTIMATED COSTS FOR

REMEDIAL ALTERNATIVE 2

Description Cost Estimate

30 Years Variable Durations Initial Capital Costs AS/SVE (TCE-impacted area) $183,600 $183,600

LNAPL Physical Barrier (off-site) $436,500 $436,500

LNAPL Extraction/Disposal (on-site and off-site) $1,185,900 $1,185,900

Groundwater/LNAPL Monitoring Network $9,700 $9,700

Soil Vapor/SVI Monitoring Network $45,000 $45,000

Limited On-site Removals $964,100 $964,100 Implement ECs and ICs (environmental

easement, SMP) $46,000 $46,000

Initial Capital Cost Subtotal: $2,870,800 $2,870,800 O&M Net Present Worth over Anticipated O&M Periods AS/SVE O&M (4 years) $1,179,400 $223,700 LNAPL Extraction (on-site and off-site, 10

years) $2,809,200 $1,222,600

Groundwater/LNAPL Monitoring (6 and 12 years) $3,208,200 $1,249,400

Soil Vapor/SVI monitoring (6 years) $889,200 $245,800

Certification and Reporting (30 years) $255,400 $255,400 O&M, Certification and Reporting Net

Present Worth Subtotal: $8,341,400 $3,196,900

Post-Remedial Capital Costs AS/SVE System Removal (4 years) $10,100 $21,800

LNAPL Extraction System Removal (10 years) $150,000 $271,000 Groundwater and LNAPL Monitoring Network

Abandonment (12 years) $19,500 $33,200

Soil Vapor/SVI Monitoring Network Abandonment (6 years) $15,600 $31,700

Post-Remedial Capital Cost Subtotal: $195,200 $357,700 TOTAL COST (initial and Post-Remediation

Capital, O&M/Certification/Reporting) $11,407,400 $6,425,400

This table was developed from previous submissions performed by FPM Group Note: Assumed interest rate is 5% and assumed inflation rate is 2%. All subtotal and total costs are rounded to the nearest $100.

Page 4-27

4.1.3 Alternative 3: Physical Barrier with LNAPL Extraction/Disposal, Option for On-site In-situ Stabilization of LNAPL, Targeted Soil Excavation and Disposal with In-Situ Chemical Treatment, Air Sparging/Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization and Vapor Barrier Soil Vapor/SVI Monitoring, and ECs/ICs

This comprehensive remedial alternative prepared and evaluated by FPM would address identified impacts in each of the Site media with the objective of removing more impacts than Alternative 2, including removal of the apparent sources of LNAPL, providing off-site containment of LNAPL, providing an option for on-site stabilization of LNAPL, and providing protection from potential exposures for all media. This alternative involves more intrusive remedial activity on-site and off-site, with associated impacts as noted in the evaluation criteria below. ECs and ICs will continue to be necessary to implement this remedy, control potential exposures during remedial activities, and control potential exposures over the long term.

In evaluating this remedial alternative, it is assumed that the current Site condition (vacant building) continues for a period of time following initial implementation of the remedy and that redevelopment includes partial excavation of the Site subsurface, facilitating certain aspects of the remedy, as described in subsequent sections. It is also assumed that the adjoining former NuHart property to the east is redeveloped.

Physical Barrier with LNAPL Extraction/Disposal

An off-site physical barrier for LNAPL and LNAPL extraction and disposal are considered as part of Remedial Alternative 3 to prevent potential LNAPL migration and to remove LNAPL from on-site and off-site areas. A sheet pile physical barrier is considered in this remedial alternative. The location of the contemplated physical barrier (off-site just to the southwest of the Franklin Street/Dupont Street intersection) is shown on Figure 4.1.3.1; proposed and potential LNAPL extraction locations are also shown on this figure. Monitoring will be necessary to confirm that LNAPL migration is not occurring and to document the removal of LNAPL over time; monitoring is discussed in a later section.

Extraction and disposal of LNAPL from the Site and off-site areas adjoining the Site is contemplated to remove LNAPL from beneath the Site, the adjoining sidewalk areas, and portions of the adjoining streets, thereby reducing the amount of LNAPL present in the environment over time and controlling potential LNAPL migration from the apparent source area.

An off-site physical barrier is also considered as part of Remedial Alternative 3 to prevent potential LNAPL migration onto the downgradient property that is planned to be developed with a school. Although LNAPL has not been identified in any of the monitoring locations adjoining this property, it is possible that LNAPL migration could be triggered by future construction activities such as dewatering that alter subsurface conditions. Therefore, to prevent potential future exposure and reduce the potential impact to the environment, a physical barrier is considered for this location. Monitoring will be necessary to assess the potential presence of LNAPL near the physical barrier. If LNAPL does migrate to the vicinity of the physical barrier, then LNAPL extraction and disposa l would be required to remove the LNAPL in proximity to the barrier. LNAPL extraction would not be implemented as part of the remedy unless LNAPL is detected in any of these wells in the future.

SHEET NO.



www.gza.com


PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 3 PHYSICAL BARRIER/LNAPLEXTRACTION LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.3.1JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONIC FILEPROVIDED BY DUPONT STREET DEVELOPERS, LLC, ENTITLED"ALTERNATIVE 3 PHYSICAL BARRIER/LNAPL EXTRACTIONLAYOUT," DATED 3/24/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY





Page 4-29

Potential LNAPL recovery well locations are shown on Figure 4.1.3.1, should LNAPL recovery become necessary.

Extraction and disposal of LNAPL from the sidewalk area adjoining portions of the east and south sides of the Greenpoint Playground in and near the area where LNAPL is present (MW-25) is also contemplated. Extraction would remove the LNAPL that is present beneath the sidewalk near well MW-25 and reduce the amount of LNAPL present beneath the west side of Franklin Street and the Franklin/Dupont Street intersection over time.

LNAPL has been identified beneath the southeastern corner of the Franklin Street/Dupont Street intersection. Extraction and disposal of LNAPL from this location is considered to remove LNAPL from beneath the sidewalk, the adjoining street, and the off-site properties in this area. A physical barrier is not contemplated for this location as it may reduce the effectiveness of LNAPL recovery.

LNAPL extraction may be accomplished using recovery wells and/or recovery trenches. As discussed in Section 4.1.2, the selection of recovery trenches or wells for each remedial area should be made following a full assessment of the implementation considerations at each location. For the purpose of this remedial alternative, it is assumed that closely-spaced recovery wells are used for off-site LNAPL recovery and more widely-spaced wells, some of which will be in soil removal areas, will be used for on-site recovery. Similarly, it is assumed that the recovery equipment includes belt skimmers installed in the extraction wells due to the high viscosity of the LNAPL to be recovered. The removed LNAPL would be temporarily contained at each off-site recovery location in a tank to be located in a subgrade vault. It is anticipated that the LNAPL recovered on-site would be stored in a centrally-located tank on-site. The LNAPL would be periodically removed from the tanks using a vacuum truck and transported for off-site disposal at an approved facility.

It may be feasible to enhance LNAPL recovery via in-situ chemical treatments, such as surfactant injection that could enhance the mobility of the LNAPL, thereby improving its recovery rate. Typically, this type of treatment is conducted after recovery has been initiated and is often used as a "polishing" method. Bench testing would be required to initially evaluate whether the Site LNAPL is amenable to chemical treatment. If bench testing is successful, then in-situ pilot testing would be required to demonstrate this method in the field and obtain information necessary for design. Pilot testing will be considered following an assessment of the performance of the on-site recovery system. For this FS, an allowance has been made for bench testing.

Costs for physical barriers and LNAPL recovery wells under this Alternative have been estimated as shown on Table 4.1.3.1. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for 30-year, 8-year and 10-year remedial periods. Based on previous experience with LNAPL recovery systems and the highly viscous nature of the LNAPL at this Site, it is anticipated that the system that will be designed for current conditions may reach the limits of its effectiveness within a few years of operation but (under this Alternative) will continue to be operated for up to 8 years to maximize LNAPL recovery. This remedial period also considers the enhanced removal of on-site source material (targeted soil removal) contemplated under this alternative. In response to a NYSDEC request, the cost for a 10-year remedial period is also provided for cost comparison between Alternatives.

Page 4-30

TABLE 4.1.3.1

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 LNAPL PHYSICAL BARRIER AND EXTRACTION/DISPOSAL


Capital Costs:

On-site Extraction Wells $623,000 $623,000


Contingency (15%) $93,400 $93,400


Reporting (15%) $93,400 $93,400

Capital Cost Subtotal (on-site): $1,058,900 $1,058,900

Off-site Barrier and Extraction Wells $683,400 $683,400


Contingency (15%) $102,500 $102,500


Reporting (15%) $102,500 $102,500

Capital Cost Subtotal (off-site): $1,161,700 $1,161,700

Total Capital Costs: $2,220,600 $2,220,600 Annual Operation, Monitoring and

Maintenance Costs: $165,100 $165,100


Extraction Systems Removal $177,100 $319,900 TOTAL COST (Capital and OM&M

Net Present Worth): $5,730,700 $3,991,500

This table was developed from previous submissions performed by FPM Group Note: All costs rounded to the nearest $100.

Page 4-31

On-site In-Situ Stabilization of LNAPL (Option)

In-situ stabilization (ISS) may be considered as an option to remediate the on-site LNAPL in lieu of on-site LNAPL recovery. ISS generally consists of mixing reagents such as cement, fly ash, blast furnace slag, Fullers Earth, soda ash, clay, and other similar materials into the subsurface and mixing them with the materials to be treated (in this case, the LNAPL and associated LNAPL-impacted soil near the water table) to create a stabilized material with a lower potential to migrate and/or dissolve into the groundwater.

ISS treatment is performed using specially-designed drill rigs that bore into the zone to be treated, inject the reagents, and mix the reagents with the soil and LNAPL. If this option is used, then the LNAPL would remain on-site and it would be treated to reduce the potential for migration and impact to groundwater. The location of the potential ISS treatment area and other LNAPL remedial measures that would be implemented under this option (off-site LNAPL barrier and extraction locations) are shown on Figure 4.1.3.1A. Monitoring will continue to be necessary to confirm that LNAPL migration is not occurring in the off-site area and to document the removal of off-site LNAPL over time; monitoring is discussed in a later section.

Implementation of ISS is performed using multiple pieces of heavy equipment and requires that subsurface obstructions be removed in the treatment area. Therefore, ISS implementation at this site would be performed following removal of the on-site building and all associated subsurface infrastructure (foundation elements, tanks, etc.) in the treatment area. If it is determined that the building overlying the treatment area is pile-supported, then ISS treatment is not likely to be feasible, since the closed spaced piles would interfere with complete mixing.

ISS treatment results in a soil volume increase in the treatment area due to the addition of significant volumes of reagent materials. To accommodate this volume increase, the area overlying the treatment zone is typically excavated to provide space for the treated material to expand into. The removal of overburden material also has the beneficial effect of reducing the power needed to operate the ISS treatment equipment. However, in the case of this site where exposed LNAPL presents a potential odor concern, it would be prudent to maintain a layer of overburden material above the LNAPL-impacted treatment zone to reduce the potential for odor issues. For the purposes of assessing this option, it is assumed that the Site surface is excavated to 9 feet below grade prior to ISS, which would result in an approximate 4-foot layer of overburden above the LNAPL and sufficient room for material expansion during ISS treatment. It is also assumed that the ISS treatment augers are equipped with shrouds to control odors and dust and that the shrouds, together with use of odor-controlling foam, are sufficient to control nuisance odors.

Although one of the goals of ISS is to reduce the mobility of LNAPL by lowering the permeability of the soil in which the LNAPL is contained, the ISS process displaces fluid in the soil pores during the injection process and can result in LNAPL migration from the treatment area during and shortly following treatment. LNAPL migration during ISS treatment may be controlled by using temporary sheeting on the outside of the treatment area, particularly if the ISS treatment cannot be initiated outside of the LNAPL-impacted area. ISS treatment typically starts at the outer edges of the treatment area and progresses inward, thereby containing LNAPL migration within the treatment area once the outer edges are completed. LNAPL recovery may be performed within and surrounding the treatment area to capture

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ALTERNATIVE 3 ISS OF LNAPL LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.3.1AJB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:


LEGEND:



IHWDS BOUNDARY





EXTENT OF THE IN-SITU STABILIZATION

Page 4-33

LNAPL that may be mobilized during ISS. For the purposes of assessing this option it is assumed that temporary sheet piles are placed near the southern, western, and northern edges of the treatment area during the initial stages of ISS treatment, that ISS treatment is started near the perimeter of the on-site LNAPL area and progresses inward, that the off-site recovery equipment is installed and operational during ISS treatment, and that LNAPL recovery is also performed from temporary recovery pits within the treatment area during the treatment process.

Prior to selection of ISS as a remedial method for the on-site LNAPL, which consists of a phthalate Hecla oil mixture, bench testing would be required to determine whether ISS is feasible for this type of LNAPL. Bench testing typically consists of a treatability study performed in a laboratory by an ISS remedial specialist. Typically, a test pit is performed on-site to obtain samples of the Site’s LNAPL and associated impacted soil. These samples are then blended with multiple reagents at varying proportions to determine the reagent blend and dosage rate needed to stabilize the material. The treated material is then tested to determine the properties of interest, which typically include unconfined compressive strength, permeability, leachability, and other relevant properties. The results of the bench testing are then evaluated to determine if ISS is an effective remedial method for the LNAPL.

If the bench testing results indicate that ISS has the potential to achieve the remedial objectives, then pilot testing is typically performed in the field to evaluate field performance issues and logistics and prepare for full-scale ISS. Pilot testing is typically performed prior to full mobilization for ISS and may include excavation of overburden, removal of subsurface obstructions, field testing of reagent mixes, injection rates, and mixing methods, assessment of odor, dust and noise concerns, evaluation of overhead and lateral clearances, assessment of injection equipment sizing and other factors needed to confirm that ISS can be successfully implemented at a site. The ISS is a process that involves chemical reactions that reduce the leachability of a waste. Stabilization chemically immobilizes hazardous materials or reduces their solubility through a chemical reaction. The physical nature of the waste may or may not be changed by this process. Therefore, the rationale of this remedy is to be stabilize the contaminants and reduce its potential for migration and further groundwater impacts, but not to remove the on-site source material. In addition, ISS would require bench and pilot testing to evaluate if it could be implemented for the LNAPL. Subsurface obstructions (foundations, utilities, and pile supports) present significant concerns. This remedy further takes a relatively immobile plume and makes it slightly less immobile. The ISS option does not remove source material and once completed, would render the phthalates unrecoverable. Application of this remedy will also restrict the future development plans for the Site. For example, the ISS option would require that foundation excavation for the new development be above the stabilized material (5 ft bgs).

Costs for ISS and associated LNAPL remedial measures under this Option (off-site LNAPL barrier and extraction locations) are estimated as shown on Table 4.1.3.1A. Backup for these costs is provided in Appendix C. It is assumed that the ISS treatment interval extends from 10 to 18 feet below grade in the treatment area. Please note that the costs have been estimated on a net present worth basis for 30-year, 8-year, and 10-year remedial periods. Based on previous experience with LNAPL recovery systems and the highly viscous nature of the LNAPL at this Site, it is anticipated that the off-site recovery systems designed for current conditions may reach the limits of their effectiveness within a few years of operation but (under this Alternative) will continue to be operated for up to 8 years to maximize LNAPL recovery. This remedial period also considers the stabilization of on-site source material contemplated under this

Page 4-34

TABLE 4.1.3.1A ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3

IN SITU SOLIDIFICATION /STABILIZATION, LNAPL PHYSICAL BARRIER AND EXTRACTION/DISPOSAL


Capital Costs:

OnSite Exterior Wells $433,800 $433,800 Engineering Design Costs (15%) $65,100 $65,100 Contingency (15%) $65,100 $65,100 Oversight and Management (25%) $108,400 $108,400 Reporting (15%) $65,100 $65,100 Capital Cost Subtotal (onsite): $737,500 $737,500 In Situ Solidification/Stabilization (ISS) $5,627,400 $5,627,400 Engineering Design Costs (15%) $844,100 $844,100 Contingency (15%) $844,100 $844,100 Oversight and Management (25%) $1,406,800 $1,406,800 Reporting (15%) $844,100 $844,100 Capital Cost Subtotal (ISS) $9,566,500 $9,566,500 Sheetpile Wall Install (Adjoining School Site) $256,800 $256,800 Offsite well installation Playground and Dupont $426,600 $426,600 Subtotal Offsite: $683,400 $683,400 Engineering Design Costs (15%) $102,500 $102,500 Contingency (15%) $102,500 $102,500 Oversight and Management (25%) $170,800 $170,800 Reporting (15%) $102,500 $102,500 Capital Cost Subtotal (offsite): $1,161,700 $1,161,700 Total Capital Costs: $11,465,700 $11,465,700 Annual Operation, Monitoring and Maintenance Costs: $143,700 $143,700

OM&M Net Present Worth $2,902,600 $1,263,200 Extraction Systems Removal $148,200 $268,800 TOTAL COST (Capital and OM&M Net Present Worth): $14,516,500 $12,997,700

This table was developed from previous submissions performed by FPM Group Note: All costs rounded to the nearest $100.

option. In response to a NYSDEC request, the cost for a 10-year remedial period is also provided for cost comparison between Alternatives.

Page 4-35

Targeted Soil Excavation and Disposal with In-Situ Chemical Treatment

Targeted soil excavation and disposal would directly address soil impacts associated with the presumed LNAPL and VOC source areas on the Site and would also indirectly address the LNAPL plume and dissolved SVOC and VOC groundwater impacts found on-site and in proximity to the Site by removing the sources of these impacts. The targeted soils under this alternative consist of LNAPL -saturated soils that may be present in proximity to the USTs and piping trench systems formerly used to store and convey phthalates and Hecla oil during the former plastic manufacturing process and the VOC-impacted soils (above the water table) in the northeastern corner of the Site. This remedial method would be implemented during Site redevelopment, which is anticipated to include partial excavation of the Site subsurface.

It should be noted that this remedial method is applicable as described below if the on-site LNAPL is to be remediated by extraction and disposal. However, if the ISS remedial option is selected for the on-site LNAPL, then excavation and disposal of the targeted source soil would be limited to the VOC source area. This possibility is addressed in the cost analysis for this remedial method.

Although this Alternative includes treatment of groundwater VOC impacts by AS/SVE (which would likely be implemented prior to redevelopment, as described below), the targeted excavation of VOC source soil to about 10 feet below grade (near or at the water table) will facilitate enhanced groundwater treatment by in-situ application of appropriate chemical treatment materials to the exposed soil/groundwater surface in the open excavation prior to backfilling. Selection and design of the in-situ chemical treatment would be made during the remedial design process. For this FS, an allowance for this enhancement of groundwater treatment has been made in the cost estimate for targeted soil excavation and disposal. This alternative would actively reduce soil contaminant concentrations by removing the targeted affected soils from the Site subsurface and replacing the impacted soils below the depth of the redevelopment excavation with clean backfill. Confirmatory (end-point) sampling would be conducted to document the condition of the remaining soil and assess if residual soil (exceeding applicable SCOs) remains present,

The estimated areas of excavation to remove the targeted impacted soil beneath the Site are shown on Figure 4.1.3.2 and encompass the areas associated with the closed-in-place USTs, the piping trench systems (not shown on the figure) formerly used to store and convey phthalates and Hecla oil, and the area where VOC-impacted soils are present above the water table. The closed USTs and piping trench systems would be removed during redevelopment and the targeted soil will be removed during UST and trench removal and consist of removal of LANPL saturated soils associated with releases from tanks, pipes and trenches within approximately one foot of the appurtances. The vertical limit of soil removal in the targeted removal areas is estimated to be about 10 feet below grade This limit was estimated based on the estimated depths of the USTs and underlying groundwater and may be changed during remedial activities based on visual observations. Excavation below the water table would not be conducted during targeted soil removal.

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ALTERNATIVE 3 TARGETED SOILEXCAVATION AREAS


AUGUST 2016 12.0076485.00

FIGURE

4.1.3.2JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 3 TARGETED SOIL EXCAVATIONAREAS," DATED 3/24/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY


EXTENT OF SOIL REMOVAL

SOIL REMOVAL AND IN-SITU CHEMICAL TREATMENT

Page 4-37

The estimated area of excavation of the VOC-impacted source soil is shown on Figure 4.1.3.2, should the ISS remedial option be used to remediate the on-site LNAPL.

For this FS, it is estimated that targeted impacted soil removal would be conducted in limited areas totaling approximately 5,400 square feet to an average depth of approximately 10 feet. The estimated volume of targeted impacted soil to be removed is about 1,600 cubic yards (not including the volume of the closed USTs). The estimated volume of targeted impacted soil would be approximately 260 cubic yards if only the VOC-impacted soil is targeted for removal (i.e. ISS option is used for LNAPL). As the targeted soil consists primarily of LNAPL-saturated soil, it is assumed that an estimated 80% of the removed soil would require disposal as hazardous waste. The remaining soil to be disposed is assumed to be non-hazardous.

Although it is assumed that additional Site soil will be removed for redevelopment purposes under this Alternative, for the purposes of this FS this additional soil removal is not considered to be a remedial activity. It is assumed that the redevelopment soil removal would be conducted under the Site Management Plan (SMP) that would be an IC for this Site (see discussion below). Soil removal under the SMP would include screening by an environmental professional and appropriate management, including removal and disposal. Although this soil will likely include historic fill, for this purposes of this FS it is assumed that this soil is not removed for remedial purposes and, therefore, the associated costs are not included in this FS.

Although odors did not present a concern during the test pit activities described in Section 2.2.2 of this FS, if the removal work is conducted once the on-site building had been removed, it is possible that odor control may be necessary during removal of the USTs, piping systems, and associated soils, particularly if these activities are undertaken during warm weather and/or large excavations are allowed to remain open. Measures to monitor and, if necessary, control odors will be implemented during excavation activities. The control measures will include limiting the size of open excavations (particularly those excavations that include LNAPL-impacted soil), performing the excavations sequentially to limit the areas of exposed soil, use of odor-control foam on odorous excavation surfaces and excavated materials as needed, covering stockpiles and loaded trucks with tight -fitting covers, limiting stockpile sizes, and promptly loading and transporting removed materials.

Confirmatory sampling for SVOCs would be conducted in the floor and sidewalls of each UST and piping trench excavation and confirmatory sampling for VOCs would be conducted in the floor and sidewalls of the VOC-impacted area to evaluate the nature of impacts that may remain present after targeted soil removal. The in-situ chemical treatment would be applied to the bottom of the excavation in the VOC-impacted area to treat residual groundwater impacts, if present. The completed excavations would require backfilling and compaction below the level of the redevelopment excavation.

Costs for the targeted soil excavation and disposal with in-situ chemical treatment alternative have been estimated as shown on Table 4.1.3.2; costs for removal of VOC-impacted soil are provided separately if the ISS remedial option is implemented. Backup for these costs are provided in Appendix C. Please note that these costs include capital costs for targeted soil removal and an allowance for in -

Page 4-38


TARGETED SOIL EXCAVATION/DISPOSAL WITH IN-SITU TREATMENT

Description Cost

Capital Costs:

Excavate/Dispose/Confirmatory Sampling/Treatment $845,300




Reporting (15%) $126,800

TOTAL COST: $1,437,000


Note: Ali costs rounded to the nearest $100.

Page 4-39

situ chemical treatment only. Costs for additional measures (ECs and ICs) that may be needed to address residual soil contamination that is not removed by excavation and in-situ treatment are addressed below.

Air Sparqinq/Soil Vapor Extraction

Under Alternative 3, AS and SVE would be used to directly address soil and groundwater VOC impacts identified on the northeastern portion of the Site and in the downgradient vicinity of the Site, like the AS/SVE system contemplated under Alternative 2. This alternative would actively reduce VOC concentrations in the affected areas by enhancing volatilization of VOCs from the groundwater. An SVE system would be used in the AS areas to remove the volatilized VOCs from the subsurface and directly reduce soil vapor impacts. Groundwater and soil vapor monitoring would be required to document the progress of remediation. Under this Alternative it is anticipated that AS/SVE would be implemented prior to redevelopment of the Site such that VOC impacts on-site and off-site may be reduced or eliminated early in the remedial process. Residual impacts that may remain present at the time of redevelopment would be further reduced or eliminated through targeted removal of source soil and/or chemical treatment, as described above.

This alternative would actively reduce VOC concentrations in the affected soil and groundwater by enhancing volatilization of VOCs, which would be captured by the SVE system, removed from the subsurface, and discharged to the atmosphere. SVE would also directly reduce VOC concentrations in unsaturated zone soils and soil vapor in the on-site and off-site areas within its ROI. Effluent monitoring would be performed to evaluate the reduction in VOC concentrations over time and to confirm that emissions from the SVE system meet regulatory requirements. The NYSDEC DAR -1 guidance document would be used to determine if effluent treatment is necessary. SVE will reduce the amount of VOCs in Site soil that have the potential to migrate to groundwater or soil vapor and would also directly remove soil vapors in the SVE treatment area, thus providing SVI mitigation within the SVE ROI.

A site plan showing the potential layout of an AS/SVE system is presented in Figure 4.1.3.3; this layout is the same as for Remedial Alternative 2. The AS portion of the system would be designed to treat areas where significant groundwater VOC contamination has been observed on-site and in close downgradient and cross gradient proximity to the on-site VOC source area. The AS system would likely include four AS wells located on-site near the source area; two of the AS wells would be positioned to treat groundwater beneath the sidewalk immediately north of this area. The AS screens would be set at a depth of approximately 18 to 20 feet to treat groundwater situated in the more permeable stratigraphic intervals above the extensive clay/silt that underlies the area. Based on previous experience with other AS systems in the NYC metro area, it is anticipated that an airflow of between 10 and 16 SCFM per well at a pressure of 20 to 40 pounds per square inch would be needed to result in an ROI of about 30 feet at each AS well. A compressor capable of a total flow of 60 to 80 SCFM at the targeted pressure is indicated.

SVE wells would be required to capture vapors resulting from sparging and would likely include three wells centered on the AS area. SVE system design would take stratigraphic variations into consideration to maximize effectiveness. It is anticipated that an SVE ROI of about 50 feet may be

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AUGUST 2016 12.0076485.00

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4.1.3.3JB

ZS

ZS

MT

JB

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N

0 30 60 120


NOTES:


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IHWDS BOUNDARY

PROPOSED AIR SPARGE WELL WITHRADIUS OF INFLUENCE



Page 4-41

achieved with a flow rate of about 100 SCFM under a vacuum of between 10 and 150 inches of water. The blower(s) would be appropriately sized for the anticipated total flow rate and vacuum of the SVE system. Sub-slab monitoring points would also be installed to just below the slab to allow for confirmation of the SVE ROl and to allow for sub-slab vapor sampling, as needed.

Costs for an AS/SVE system to treat the VOC source area have been estimated as shown on Table 4.1.3.3. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for both a 30-year remedial period and a four-year remedial period. Based on previous experience with AS/SVE systems, the AS/SVE system is anticipated to reach the limits of its effectiveness within about four years of operation.


Groundwater and LNAPL monitoring is considered as part of Remedial Alternative 3 to provide the data needed to confirm that the identified groundwater impacts are being reduced by the active remedial methods. LNAPL would also be monitored to confirm that migration is not occurring and to document the anticipated reduction in LNAPL extent and apparent thickness in the on-site and off-site areas over time. This alternative would not actively reduce groundwater contaminant concentrations or LNAPL, but would provide for assessment of the anticipated reduction in groundwater impacts and LNAPL extent and apparent thickness over time due to other factors, such as remediation of other affected media and ongoing natural processes.

Groundwater and LNAPL monitoring would be conducted at select wells downgradient, cross gradient, and upgradient of the Site. Figure 4.1.3.4 shows the proposed locations of groundwater monitoring wells (blue circles) and LNAPL monitoring wells (green circles) to be included in the monitoring networks and assumes that the ISS remedial option is not implemented. For reference, the locations of the off-site LNAPL plume, the area of TCE-impacted groundwater, and proposed physical barrier and LNAPL extraction wells are also depicted on Figure 4.1.3.4. All the wells presently exist except for two wells that would be needed near the edges of the existing on-site LNAPL plume. It is anticipated that some wells of the wells may require replacement following excavations for redevelopment and/or ISS treatment; costs for well replacement are included in this alternative. Groundwater monitoring for most of the wells would be conducted semiannually (twice per year) and groundwater monitoring around the AS/SVE system (MW-3, MW-8, MW-13, MW-18, MW-34, MW-35, MW-39 and MW-40) would be conducted quarterly to assess the progress of remediation. LNAPL monitoring would be conducted monthly. The monitoring frequencies would remain unchanged until the NYSDEC approves a change in monitoring frequency.

Costs for groundwater/LNAPL monitoring have been estimated as shown on Table 4.1,3.4 and are presented on a projected net present worth basis over 30 years and over variable durations coordinated with the potential duration of remedial systems operations. Backup for the estimated costs for this alternative are included in Appendix C.

Page 4-42


AIR SPARGING/SOIL VAPOR EXTRACTION


Capital Costs



Contingency (15%) $16,200 $16,200


Reporting (15%) $16,200 $16,200




ASISVE System Removal $6,900 $14,800



Notes:

Assumed interest rate is 5% and assumed inflation rate is 2%.

All costs rounded to the nearest $100

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AUGUST 2016 12.0076485.00

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4.1.3.4JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:


LEGEND:



IHWDS BOUNDARY








Page 4-44

TABLE 4.1.3.4

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 GROUNDWATER/LNAPL MONITORING


Capital Costs:


Engineering Design (15%) $3,200 $3,200

Contingency (15%) $3,200 $3,200


Reporting (15%) $3,200 $3,200









Page 4-45

Sub-Slab Depressurization and Vapor Barrier

Sub-slab depressurization systems (SSDS) and, as feasible; vapor barriers would be used to prevent potential impacts to indoor air quality that may occur due to SVI. Under Alternative 3 an SSDS with a vapor barrier is contemplated for the portion of the off-site property (adjoining NuHart facility building to the east) beneath which ICE-impacted soil vapors have been identified and the potential for SVI has been documented. The SSDS and vapor barrier would not significantly reduce VOC concentrations in the sub-slab soil vapor, but would significantly reduce the potential for migration of soil vapors into indoor air. SVI monitoring would be used in conjunction with the SSDS and vapor barrier to confirm that SVI is not occurring. Additional monitoring points would be necessary to optimize the operation of the SSDS.

As noted above, this Alternative assumes that some remedial activities (such as implementation of AS/SVE) will be conducted prior to Site redevelopment and that redevelopment will include targeted soil excavations for remediation and additional limited soil excavation for construction purposes. Although the use of the sub-grade portion of the new Site building is not established, it is likely that this crawlspace area would be used for remedial equipment and the overlying first floor would be used primarily for parking, with no occupancy. Under this Alternative it is assumed that the remedial activities conducted prior to redevelopment will significantly reduce VOCs in on-site and off-site soil vapors and that the on-site subgrade area will include a concrete floor and be ventilated in accordance with New York City criteria for subgrade parking garages. Therefore, an SSDS is not planned for the Site. A vapor barrier would be installed on-site as needed for typical construction in an urban area.

SSDS construction would require installation of lateral piping beneath the off-site building. The existing soil vapor data from the RI Report indicate that soil vapor impacts are present beneath the westernmost portion of the adjoining off-site property to the east, but are not present beneath the eastern-most portion of this property. These data are supported by sub-slab soil vapor data obtained during the recent RI of Lot 57 of the NuHart property, which was conducted under the oversight of the New York City Office of Environmental Remediation (OER). This investigation documented that there were no detections of TCE or its breakdown LNAPLs in any of the sub-slab soil vapor samples from beneath Lot 57. Additional soil vapor will be obtained for the off-site NuHart property (the lots closest to the Site are e-designated) and assessed to determine the extent to which mitigation is required. However, for the purposes of this FS the existing data were used to develop a conceptual layout for the off-site SSDS.

For the purposes of evaluating Alternative 3, it is assumed that lateral piping (and an associated vapor barrier) is installed beneath a new building on the adjoining NuHart facility to the east. As the amount of piping to be installed is significant, pilot testing would be required to confirm the anticipated ROI of the SSDS laterals prior to design of the individual SSDS components and to assess the interaction between the SSDSs and the SVE remedial system that would be instal led under this alternative. A potential layout of the SSDS laterals is shown on Figure 4.1.3.5 and considers the potential SVE layout and the documented extent of soil vapors extending beneath the off-site property. The actual design of the SSDS would be developed during the remedial design phase and would incorporate any additional soil vapor data obtained from the NuHart property.

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ALTERNATIVE 3 SSDS LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.3.5JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 3 SSDS LAYOUT," DATED 3/24/16,ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY



PROPOSED SSDS LATERALS


POTENTIAL SUCTION POINT

Page 4-47

Installation of SSDS laterals and a vapor barrier would be conducted during construction of a new building on the adjoining former NuHart facility to the east. The vapor barrier would be placed above the SSDS laterals and beneath the slab and would extend under the entire area of the e-designated lots on the NuHart property. The lateral piping would be connected to one or more blowers which would then discharge via a stack to the atmosphere; for the purposes of evaluating Alternative 3 it is assumed that one blower is used. The potential flow rates for the horizontally -piped SSDS would be approximately 100 standard cubic feet per minute at a vacuum of up to 20 inches of water per leg of the system. SSDS equipment would be housed in an enclosure within the building; the enclosure would be insulated to reduce noise, ventilated to control temperature, and equipped with typical automated monitoring equipment and alarm systems.

Under this Alternative, SSDSs will be implemented to mitigate SVI for the off-site buildings on the north side of Clay Street (15 and 19 Clay Street) in proximity to the area where TCE-impacted soil vapor has been identified if SVI is confirmed (via monitoring) to be occurring. For this option, it is assumed that access is provided for monitoring and for SSDS suction point installation. Potential SSDS suction point locations on the north side of Clay Street are shown on Figure 4.1.3.5.

Costs for SSDS design, construction, and monitoring, including contingency costs for SVI mitigation on the north side of Clay Street, have been estimated as shown on Table 4.1.3.5 and are presented on a projected net present worth basis over 30 years. It is possible that other remedial measures, such as the AS/SVE system and targeted soil removal, will reduce the soil vapor levels sufficiently such that SSDS operation is no longer necessary. Therefore, we have also projected SSDS costs over six years (two years beyond the anticipated completion of AS/SVE remediation, as discussed above). Backup for the estimated costs for this alternative are included in Appendix C.


Monitoring for soil vapors and potential SVI is considered as part of Remedial Alternative 3 to assess the anticipated improvement in soil vapor conditions over time due to remedial activities and confirm that soil vapor impacts present beneath the pavement/sidewalks of nearby off-site areas do not affect indoor air quality at occupied structures. The monitoring activities would not actively reduce VOC concentrations in the soil vapor, but would be used to evaluate potential exposure issues, to assess reductions in VOC concentrations in soil vapor that are anticipated result from other remedial measures, and to assess whether the SVI mitigation measures (described below) are effective.

Soil vapor/SVI monitoring would include installation of vapor implants through the existi ng Site building slab (including locations to the south and west of the vapor source area), through nearby sidewalks at several key locations, and through the slab of the targeted off-site building (adjacent NuHart facility) in the area where TCE vapors have been identified to monitor soil vapors over time. SVI monitoring would also include installation of vapor implants through the slabs of key off-site buildings (15 and 19 Clay Street) to allow for monitoring of sub-slab soil vapor and indoor air to be conducted periodically. SVI monitoring would require that building access for implant installation

Page 4-48

TABLE 4.1.3.5

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER

Description Cost

(30 Years)

Cost

(6 Years)

Capital Costs

SSDS and Vapor Barrier Installation $214,300 $214,300


Contingency (15%) $32,100 $32,100


Reporting (15%) $32,100 $32,100




SSDS Removal $13,000 $26,400



Notes:

Assumed interest rate is 5% and assumed inflation rate is 2%.

All costs rounded to the nearest $100

Page 4-49

and sampling be obtained from the off-site property owners and that access for indoor air sampling be obtained from building occupants. For the purposes of this FS it is assumed that access to off-site properties is obtained. Figure 4.1.3.5 (previously presented) shows the proposed locations of the soil vapor monitoring points and SVI monitoring points at the adjacent NuHart facility. SVl monitoring point locations for the other off-site properties would be selected in consultation with off-site property owners.

Soil vapor and SVI monitoring is anticipated to be conducted at an initial frequency of twice per year (once during the heating season and once during the cooling season). During each monitoring event co-located sub-slab soil vapor and indoor air samples, an ambient air sample, and soil vapor samples (from the non-SVI locations) would be collected for laboratory analysis. All procedures and data evaluation would be in accordance with NYSDOH guidance. Monitoring would be continued until the NYSDEC approves termination of monitoring.

Costs for soil vapor and SVI monitoring have been estimated as shown on Table 4.1.3.6 and are presented on a projected net present worth basis over 30 years and over a six-year period as soil vapor conditions are anticipated to improve after the source soil is remediated via AS/SVE and targeted soil removal. A monitoring frequency of twice per year is assumed. Backup for the estimated costs for this alternative are included in Appendix C.


Implementation of ECs and ICs would be used to control potential exposures to impacts for all media under Remedial Alternative 3. Specifically, soil impacts and LNAPL (or stabilized LNAPL) will remain present on-site and LNAPL will remain present off-site in areas, although these will decrease over time. Soil vapor and groundwater impacts may also remain present, but are anticipated to diminish over time. ECs and ICs considered include a cover system EC (building slab for the Site and existing sidewalks and road pavement for off-site areas) to provide protection from impacted soil and LNAPL, and ICs (Site and groundwater usage restrictions, and an SMP) to control Site use and potential on-site exposures to soil, soil vapor, LNAPL, and/or groundwater. Access to the off-site subsurface is presently controlled by an IC consisting of a street-opening permit process that is required for penetration of the existing EC (sidewalks/pavement). An additional IC will be needed to control potential exposures during off-site subsurface activities that are conducted to depths where Site-related LNAPL and associated impacted soil are present. The IC considered under this alternative is posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present.


Costs for the ICs and ECs, including implementation of an environmental easement, SMP, annual inspections and cover system repairs, certification and reporting, have been estimated as shown on

Page 4-50




Cost (6 Years)

Capital Costs:


Contingency (15%) $3,500 $3,500

Design (15%) $3,500 $3,500


Reporting (15%) $3,500 $3,500








Page 4-51

Table 4.1.3.7 on a net present worth basis over an assumed 30-year monitoring period. Backup for the estimated costs for this alternative are included in Appendix C.

Comprehensive Remedial Alternative 3 was evaluated relative to the nine criteria as follows:

Threshold Criteria

Overall protection of public health and the environment: This alternative actively addresses groundwater, soil, and soil vapor VOC impacts within the AS/SVE system ROls, provides active protection from SVI (via the SSDS) for the off-site area where the potential for SVI is documented, and provides for additional protection from SVI (vapor barrier) for the potential new building t o be constructed on the adjoining property to the east. This alternative is also anticipated to indirectly reduce groundwater VOC impacts outside and downgradient of the AS ROI. Therefore, this alternative is considered protective of public health and the environment in that contaminants in groundwater, soil, and soil vapor will be reduced or eliminated. This alternative also actively reduces the amount of LNAPL on-site and off-site and controls potential LNAPL migration and is, therefore, protective of public health and the environment in that LNAPL will be considerably reduced and potential off-site migration controlled. This alternative also provides a means of assessing the anticipated reduction of contaminant concentrations in soil, groundwater, and soil vapor, evaluating the extent and apparent thickness of LNAPL over time, and assessing potential exposures to soil vapor via SVI. Potential public exposures to residual impacted materials would be controlled and monitored via ECs and ICs. This alternative , once fully completed, is more protective than Alternative 1 (No Action) and Alternative 2, but not as protective as Alternative 4;

Compliance with SCGs: This alternative provides for compliance with SCGs for VOCs in soil,

groundwater and soil vapor in the VOC treatment area, which encompasses much of the VOC-impacted area, as VOC concentrations are anticipated to be reduced to near or below the SCGs within and downgradient of this remedial area. This alternative provides for partial compliance with SCGs relative to LNAPL in the on-site and off-site areas as LNAPL in the source area will be removed via excavation (or stabilized via ISS) near the former sources and removed over time via extraction, potential off-site migration will be controlled, and the extent and apparent thickness of off-site LNAPL are anticipated to be reduced over time. This alternative does not directly provide for compliance with groundwater SCGs for other constituents (SVOCs), but does provide a means for evaluating achievement of SCGs in groundwater due to remediation by other measures and ongoing attenuation processes. This alternative does not directly provide for compliance with SCGs in soil vapor outside of the VOC treatment area, but it does provide for mitigation of SVI concerns via implementation of an SSDS in the off-site area(s) where soil vapors are documented and a vapor barrier for new construction in the off-site NuHart property. This alternative also provides a means for assessing achievement of SCGs in soil vapor that may result from VOC remediation, and for evaluating compliance with the SCGs for indoor air in occupied buildings. This alternative includes ECs and ICs to monitor and control potential exposures for those media where SCGs are not obtained, thereby assuring that the SCGs are not exceeded at potential exposure points;

Page 4-52

TABLE 4.1.3.7

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 IMPLEMENT ECS AND ICS


Capital Costs:









http://cert.net/

Page 4-53

Balancing Criteria

Long-term effectiveness and permanence: The VOC contaminants in the groundwater, soil, and soil vapor within the AS/SVE ROls would be actively and permanently reduced by this alternative, resulting in an effective and permanent long-term remedy for VOCs in this area. This alternative includes removal (or stabilization) of LNAPL from the vicinity of the former on-site source(s), removal and off-site disposal of LNAPL over time, and controlling potential off-site migration, thus permanently controlling and reducing the amount of LNAPL in the subsurface. Groundwater and LNAPL monitoring does not provide a long-term effective or permanent remedy for groundwater impacts or LNAPL, but it provides a means to document changes in groundwater quality and LNAPL extent and apparent thickness due to other remedial measures and attenuation processes. The SSDS(s) does not significantly remedy soil vapor impacts; however, SSDS operation will gradually reduce soil vapor impacts within its ROI over time and provide long-term effective protection from SVI. Soil vapor and SVI monitoring do not actively remedy soil vapor impacts. However, soil vapor and SVI monitoring do provide a means for documenting changes in soil vapor conditions and the potential for SVI due to other remedial measures and are a long-term effective means for assessing soil vapor conditions and the potential for SVI. Implementation of ECs and ICs will result in an effective long-term remedy from the standpoint of public health as the residual materials remaining after remediation is complete would be isolated from public contact by a cover, prohibition of groundwater usage, controls on Site usage, controls on off-site subsurface access, and an SMP to govern management of residual materials. Periodic inspection and certification would be required, resulting in an effective and permanent long-term remedy;

Reduction of toxicity, mobility, or volume: This alternative provides for a reduction of toxicity, mobility and volume of VOC contaminants in the groundwater, soil, and soil vapor within the AS/SVE ROls. This alternative also provides for a moderate reduction of toxicity, mobility and volume of LNAPL. It does not directly provide for a reduction of the toxicity, mobility, or volume of other groundwater contaminants, but does provide a means for evaluating reductions in other groundwater contaminants due to other remedial measures or attenuation processes. This alternative does not directly reduce the toxicity, mobility, or volume of soil vapor contaminants except within the SVE ROI, but it does provide a means to evaluate reductions in soil vapor contaminants due to other remedial measures. The mobility of soil vapor contaminants would be reduced via operation of the SSDS(s), implementation of a vapor barrier for new construction, and maintaining the cover EC using ICs;

Short-term impacts and effectiveness: The short-term adverse environmental impacts or human exposures would be variable during the activities associated with implementing the Alternative 3 remedial measures. Short-term adverse environmental impacts or human exposures are anticipated to be minimal to moderate for the on-site targeted removals, LNAPL recovery, and ISS aspects of Alternative 3. Although the targeted removals (and ISS, if feasible) are anticipated to be conducted after the existing Site building is removed, measures will be taken to control potential odors, construction-related noise, and impacts from vehicle activity. We will evaluate whether the targeted removals can occur while the building remains to further reduce short term impacts. As additional intrusive activity will occur relative to Alternative 2,

Page 4-54

there is the potential for more short-term impacts than for Alternative 2. The short-term adverse environmental impacts or human exposures are anticipated to be minimal for the AS/SVE remedial system, groundwater/LNAPL monitoring, soil vapor and SVI monitoring, and SSDS(s). The intrusive activities for SSDS construction and off-site vapor monitoring point construction would, of necessity, take place inside the off-site buildings. For all remedial activities, an approved HASP and CAMP would be required for the remedial construction and monitoring work and PPE would be utilized by remedial workers to control exposures. CAMP monitoring results would be used to verify that short-term impacts are minimized and to trigger implementation of additional controls if needed. Potential exposures to VOC emissions will be monitored via SVE and SSDS effluent sampling and emissions controls will be used if necessary to ensure that emissions meet Air Guide 1 requirements. Short-term adverse environmental impacts or human exposures are not anticipated in association with implementing ECs and ICs. Following completion of remedial construction and associated cover repairs, there are not anticipated to be any human exposures as the remaining affected media will be covered and the cover would be monitored;

Implementability: There are anticipated to be some technical limitations to implementing certain aspects of this alternative. For the targeted removals, as the associated excavations will be somewhat deeper than those for Alternative 2, it is anticipated that there will be an increased risk of encountering subsurface issues (utilities, old foundations, cobble zones, etc.) that may affect excavations. ISS would require bench and pilot testing to evaluate if it could be implemented for the LNAPL, and subsurface obstructions (foundations, utilities, and pile supports) present significant concerns. Since readily-available AS/SVE and SSDS remedial and monitoring technologies would be utilized, most the proposed monitoring network is already present, there is no groundwater usage, and groundwater, LNAPL, and soil vapor/SVI monitoring procedures have already been conducted under the NYSDEC-approved work plans, there do not appear to be significant technical limitations to these aspects of Alternative 3. Design of the AS and SVE systems will need to take stratigraphic variations into account. Access issues may limit off-site SVI monitoring and SSDS suction point installation. An SMP and an environmental easement would be required, both of which may be readily implemented. The existing street-opening permit process is anticipated to facilitate implementation of the off-site IC, which is anticipated to be posting of an environmental notice for street-opening permits in the Site vicinity. It is anticipated that this alternative would be implemented in stages, each of which may last at least several months; the overall construction period for this alternative is anticipated to be one to two years and will be affected by the redevelopment schedule;

Cost-effectiveness: This alternative provides long-term and short-term effectiveness and results in reductions in toxicity, mobility, and volume for VOCs in groundwater, soil and soil vapor within the AS/SVE system's ROls. This system is also likely to indirectly reduce groundwater and soil vapor impacts outside of the ROI. The SSDS will also provide long-term and short-term effectiveness, but will not result in significant reductions in toxicity or volume of soil vapor VOCs (although mobility will be significantly reduced). This alternative also provides long-term and short-term effectiveness for control of potential LNAPL migration off-site via the physical barrier, ISS (if implemented), and on-site and off-site recovery systems and results in reductions in toxicity, mobility, and volume for LNAPL in the areas where removal occurs via excavation or

Page 4-55

extraction. Design, construction and operating costs for the off-site LNAPL removal system will be moderate to high. AS/SVE remedial system and SSDS design, installation, operation, and monitoring costs are anticipated to be moderate, and the groundwater, LNAPL, soil vapor, and SVI monitoring design and implementation costs are relatively low. Overall, the costs for this comprehensive alternative are moderate, proportionally, relative to its overall effectiveness. The cost-effectiveness for the remedial and monitoring components are increased somewhat when used in conjunction with the ECs/ICs that control potential exposures;

Land use: This alternative is protective of the current and reasonably-anticipated land use of the Site, which is presently vacant and anticipated to be redeveloped with a restricted residential and/or commercial use, as the soil, groundwater and soil vapor impacted by VOCs within the AS/SVE system ROI would be remediated, mitigation of potential on-site SVI concerns would occur, LNAPL will be removed from the source area (or stabilized) and off-site areas, potential off-site migration of LNAPL would be controlled, groundwater use is not occurring or contemplated, a cover will remain present over impacted materials, and monitoring data would be available to assess LNAPL changes, groundwater quality, and potential SVI concerns on-site. This alternative is also protective of the current and reasonably-anticipated land use in the Site vicinity, as the AS/SVE system is anticipated to reduce or eliminate off-site soil, groundwater and soil vapor impacts thereby mitigating potential SVI concerns, additional SVI mitigation would be provided by the SSDS(s), LNAPL will be removed, groundwater use is not occurring, a cover will remain present or be re-installed over impacted materials, and monitoring data would be available to assess changes in the condition of subsurface media over time. Under Alternative 3 materials exceeding applicable SCGs would be isolated from the public via cover, controls on land use, and controls on groundwater use. These controls would be implemented on-site via an environmental easement and an SMP and off-site via the existing street-opening permit process and posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present;

Modifying Critetia

Community Impact: The on-site remedy consists of installation of LNAPL recovery system, AS/SVE, target excavation, and ISCO. This remedy will not require the demolition of the existing building covering the Registry Site for remedial construction.

Traffic: This alternative is not anticipated to significantly impact traffic during this timeframe. Most of the traffic increases will stem from material deliveries and employees travelling to and from the Site. During the limited on-site removals, there will be an increase in truck traffic as waste haulers will be utilized to remove soil from the Site. The anticipated waste stream for this material would be a combination of urban fill and hazardous waste which will be transported by a combination of triaxles and long haul trailers, respectively. The trucking during this portion is set for localized excavation areas and is not anticipated to have a long-term impact on traffic patterns.

Noise: This alternative will utilize heavy construction vehicles to install the LNAPL extraction wells, AS/SVE wells and limited on-site removals. Remedial construction elements will provide

Page 4-56

a short-term impact on noise levels during installation and operation. The elements of this remedy can be installed, operated and/or performed within the existing building footprint which would greatly reduce noise impacts. It is assumed that Site development would be planned around the system and eventually the equipment would be installed within the building structure.

Air Quality: This alternative is not anticipated to significantly impact air quality. It is noted that during the remedy, community air monitoring will be performed during all intrusive activities. All extracted vapors from the AS/SVE system will be treated adhere to NYSDEC standards prior to discharge. Due to the short time frame of the installation of the remedial components, exhaust from the heavy machinery is not anticipated to be significant.


The ISS portion was not considering in the above categories but would significantly impact all the categories. ISS would require demolition of the existing building and construction of an environmental enclosure during the stabilization remedy. The environmental enclosure system would significantly impact traffic during the mobilization and erection. Due to the nature of the environmental enclosure and the location of the Site with respect to adjacent buildings, the enclosure would encompass as much of the Registry Site footprint as possible. Due to the size of the Registry Site, it may be necessary to move the tent into two locations. During delivery, several double sized tractor trailers would be mobilized to the Site with loads of skins (tarping), purlins, gables and girts and structural steel to begin the erection process. In addition, a crane will be necessary to install portions of the structural frame. During mobilization and erection, it is likely that the Remedial Contractor will apply for permits to shut down Dupont Street in its entirety and one lane of Franklin street to facilitate the installation. Once the frame is installed, the skins of the environmental enclosure are required to be stretched out to slide them up the tracks in the structure. To accommodate this, the Remedial Contractor may elect to apply for permits to shut down Franklin Street for this operation. After erection, counterweights and anchors will need to be installed at the perimeter of the tent to secure it to the ground. Once the enclosure is up, multiple air handling units will be necessary to transfer air to the enclosure and collect and treat outgoing air. Air handlers typically are fueled by diesel gasoline. The air handling units are the approximately the size of a triaxle truck. During operation, it is anticipated the Remedial Contractor will request a sidewalk and lane closure on Franklin Street, Sidewalk and No Parking Restrictions on Clay Street and Sidewalk and No Parking Restrictions on Dupont Street.

The total estimated costs for Remedial Alternative 3, excluding ISS, are shown on Table 4.1.3.8. ISS of the on-site LNAPL is not recommended as part of this Alternative due to its limited compliance with SCGs, questionable implementability, and excessive cost.

Page 4-57



Description Cost

30 Years Variable Durations

Initial Capital Costs LNAPL Physical Barrier and Extraction/Disposal $2,220,600 $2,220,600 Targeted Soil Excavation/Disposal w/In-situ Treatment $1,437,000 $1,437,000 AS/SVE (TCE-impacted area) $183,600 $183,600 Groundwater/LNAPL Monitoring Network $36,600 $36,600 SSDS and Vapor Barrier $364,200 $364,200 Soil Vapor/SVI Monitoring Network $39,600 $39,600 Implement ECs and ICs (environmental easement, SMP) $46,000 $46,000 Initial Capital Cost Subtotal: $4,327,600 $4,327,600 O&M Net Present Worth over Anticipated O&M Periods LNAPL Extraction (on-site and off-site, 10 years) $3,333,000 $1,451,000 AS/SVE (4 years) $1,179,400 $223,700 Groundwater/LNAPL Monitoring (6 and 10 years) $3,187,300 $1,126,500 SSDS (6 years) $1,578,700 $436,300 Soil Vapor/SVI monitoring (6 years) $972,800 $268,900 Certification and Reporting (30 years) $255,400 $255,400 O&M, Certification and Reporting Net Present Worth

Subtotal: $10,506,600 $3,761,800

Post-Remedial Capital Costs LNAPL Extraction System Removal (10 years) $177,100 $319,900 AS/SVE System Removal $6,900 $14,800 Groundwater and LNAPL Monitoring Network

Abandonment (10 years) $19,500 $35,200

SSDS Removal (6 years) $13,000 $26,400 Soil Vapor/SVI Monitoring Network Abandonment (6

years) $16,000 $32,600

Post-Remedial Capital Cost Subtotal: $232,500 $428,900 TOTAL COST (Initial and Post-Remediation Capital,

O&M/Certification/Reporting) $15,066,700 $8,518,300

Total Cost with ISS $24,261,500 $17,713,100 This table was developed from previous submissions performed by FPM Group Note: Assumed interest rate is 5% and assumed inflation rate is 2%. All subtotal and total costs are rounded to the nearest $100.

Page 4-58

4.1.4 Alternative 4: Soil and LNAPL Excavation and Disposal, LNAPL Physical Barriers and Extraction/Disposal, Groundwater Air Sparging /Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization, Soil Vapor/SVI Monitoring, and ECs/ICs

This comprehensive remedial alternative prepared and evaluated by FPM would address identified impacts in each of the Site media with the objective of returning the Site and vicini ty to pre-release conditions to the extent practicable for all media. Although the goal of this alternative would be to maximize remediation, ECs and ICs will continue to be necessary to implement this remedy, control potential exposures during remedial activities, and in the likely event that pre-release conditions are not obtained, control potential exposures over the long term.

In evaluating this remedial alternative, it is assumed that following excavation and disposal of the on-site soil and LNAPL the Site is restored to a condition that supports redevelopment with a new building as contemplated (below-grade crawlspace and first floor parking). It is also assumed that the upper floors of this building are intended to be occupied; the remedial measures were developed accordingly.

Soil and LNAPL Excavation and Disposal

Soil and LNAPL excavation and disposal would directly address soil impacts associated with the presumed LNAPL source areas on the Site, soil impacts in proximity to the LNAPL plume, VOC -impacted soils in the northeastern portion of the Site, and remove as much of the on-site LNAPL plume as feasible. This remedial method would also indirectly address the dissolved SVOC groundwater impacts found on-site and in proximity to the Site by removing the sources of these impacts. The targeted soils under this alternative consist of LNAPL-saturated soils that may be present in proximity to the USTs and piping trench systems formerly used to store and convey phthalates and Hecla oil during the former plastic manufacturing process, on-site LNAPL-saturated soils in proximity to (above, within, and below) the LNAPL plume, and VOC-impacted soils in the northeastern portion of the Site. This alternative would actively reduce soil contaminant concentrations by removing the targeted affected soils from the Site subsurface and replacing the impacted soils with clean backfill. The LNAPL source would also actively be removed. Confirmatory (end-point) sampling would be conducted to document the condition of the remaining soil and assess if residual soil (exceeding applicable SCOs) remains present.

The area of excavation to remove the impacted soil beneath the Site (approximately 210 feet by 190 feet) is shown on Figure 4.1.4.1 and encompasses the closed-in-place USTs, the on-site LNAPL plume area, and the area where VOC-impacted soil is present in the northeastern portion of the Site. The closed USTs, associated piping, and piping trenches would also be removed during this remedial process. The vertical limit of soil removal in the area of LNAPL impact is based on the test pit results described in Section 2.2.2 of this document; excavation to an approximate elevation of -2 feet relative to NAD 1988 (approximately 16 feet below the Site building floor) is estimated to remove the LNAPL-impacted soil in this area. Soil removal to 16 feet below the Site building floor in the area of VOC impact is anticipated to remove nearly all the VOC-impacted soil. Some soil below 16 feet exhibits VOC impacts; this soil will be remediated using an alternate method, as described below.

SHEET NO.



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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 4 SOIL AND LNAPL EXCAVATION AREA


AUGUST 2016 12.0076485.00

FIGURE

4.1.4.1JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONIC FILEPROVIDED BY DUPONT STREET DEVELOPERS, LLC, ENTITLED"ALTERNATIVE 4 SOIL AND LNAPL EXCAVATION AREA,"DATED 3/29/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY


EXTENT OF SOIL/LNAPL REMOVAL

Page 4-60

The estimated volume of all soil to be excavated and disposed under this remedial alternative is 22,500 cubic yards. This volume does not include the estimated volume of the Site building slab or closed USTs. The estimated volume of LNAPL-saturated soil to be removed (including soil in potential release areas) is 5,220 cubic yards, of which an estimated 900 cubic yards may contain low-level PCBs. Both types of soil will require disposal as hazardous waste. The estimated volume of VOC-impacted soil is 1,380 cubic yards. The remaining soil (estimated as 15,900 cubic yards) is anticipated to include non-hazardous historic fill and unimpacted native soil. Although it may be feasible to segregate some of the unimpacted native soil and demonstrate through testing that it meets 6 NYCRR Part 375 and DER-10 criteria for on-site reuse, for the purposes of this FS it is assumed that segregation of significant quantities of unimpacted native soil will not be feasible and that this soil will require off-site disposal as non-hazardous waste.

For this FS it is assumed that the excavation and removal process would be conducted in a phased approach and proceed sequentially across the Site, such that the actual excavation area at any time would be smaller than the total area to be excavated. This approach, while potentially extending the total time that excavation work would be conducted, would allow for better management of equipment and truck traffic, reduce potential odor impacts, reduce dewatering needs, and facilitate improvements in excavation procedures and materials management throughout the process.

Shoring would be required for the entire perimeter of the excavation area to an estimated depth of approximately 30 feet due to the proximity of public sidewalks, streets, utilities, and other infrastructure to the excavation area. Shoring would be placed following demolition of the above -grade portions of the Site building and the actual shoring depth would be determined during remedial design. Shoring is anticipated to be placed just inside of the existing building footings, some of which may remain in place following building demolition. Shoring to the north, west and south would remain in place following the completion of excavation to limit LNAPL that may remain outside of the excavation from re-entering the remediated area. The shoring, which is anticipated to consist of a physical barrier may mitigateoff-site LNAPL that remains on-site following remediation, as discussed in the next section.

Although odors did not present a concern during the test pit activities described in Section 2.2.2 of this FS, it is possible that odor control may be necessary during excavation into LNAPL -impacted materials, particularly if these activities are undertaken during warm weather and/or large excavations remain open. Measures to monitor and, if necessary, control odors will be implemented during excavation activities. The control measures will include limiting the size of open excavations (particularly those excavations that extend to the depth of the LNAPL), use of odor-control foam on odorous excavation surfaces and excavated materials as needed, covering stockpiles and loaded trucks with tight-fitting covers, limiting stockpile sizes, and promptly loading and transporting removed materials.

If necessary to control odors that cannot be controlled by other means, the excavation and waste -management areas will be shrouded with a tent to completely contain the odorous materials. The tent will be ventilated with a high-capacity ventilation system to maintain a negative pressure inside of the tent (relative to the ambient atmosphere), with the exhaust treated as needed to reduce odor

Page 4-61

and discharged via a stack that extends sufficiently above the building to disperse any remaining odor. Pilot testing will be performed during the remedial design process to assess the potential need for a tent enclosure and ventilation system for odor control. For the purposes of this FS the costs of pilot testing are included in the estimated design costs and the costs for a tent enclosure and ventilation system are provided as an alternate cost.

Excavation to 16 feet bgs will also require dewatering in the deeper interval of the excavation. Dewatering will include removal of the LNAPL within the excavation area. Dewatering efforts would require close coordination to ensure that the LNAPL is effectively removed prior to significant lowering of the groundwater so as not to result in further soil contamination. Once the excavation reaches a depth sufficient to allow for LNAPL removal, the LNAPL would be skimmed from the bottom of the excavation and disposed off-site as hazardous waste. Once LNAPL was significantly removed, then further excavation would be conducted with dewatering as needed. LNAPL would be removed from the dewatering fluids and transported for off-site disposal as hazardous waste. Discharge of groundwater from dewatering is anticipated to be to the sewer system under a dewatering permit. Groundwater treatment (LNAPL removal, entrained particulate removal, and PCB and VOC treatment, as needed) will be required to confirm that the discharge meets permit limits.

Confirmatory soil sampling for SVOCs and VOCs (depending on the location) would be conducted in the floor of the excavation to evaluate the nature of impacts that may remain present after soil removal. The completed excavations would require backfilling and compaction to address safety concerns and prepare the Site surface for redevelopment.

Costs for the soil and LNAPL excavation and disposal alternative have been estimated as shown on Table 4.1.4.1. Backup for these costs are provided in Appendix C. Please note that these costs include capital costs for soil and LNAPL removal in the targeted area only. Costs for additional measures, including ECs and ICs, needed to address soil and LNAPL contamination that is not removed by excavation are addressed below.

LNAPL Physical Barriers and Extraction/Disposal

Physical barriers and LNAPL extraction and disposal are considered as part of Remedial Alternative 4 to prevent potential LNAPL migration onto an off-site property that may be developed with a school and between on-site and off-site areas, and to remove LNAPL from off-site areas. Monitoring will be necessary to confirm that LNAPL migration is not occurring and to document the removal of LNAPL over time; monitoring is discussed in the following section.

Shoring, which is anticipated to consist of a physical barrier, will be placed around the entire perimeter of the on-site excavation area to an estimated depth of approximately 30 feet, as discussed above and shown in Figure 4.1.4.2.

Page 4-62

TABLE 4.1.4.1

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 SOIL AND LNAPL EXCAVATION AND DISPOSAL

Description Cost

Capital Costs:

Sheet piling/Excavate/Dispose/Confirmatory Sampling $9,275,600

Contingency (15%) $1,391,300

Engineering Design (15%) $1,391,300

Oversight and Management (25%) $2,318,900

Reporting (15%) $1,391,300

TOTAL COST: $15,768,400

Alternate Costs for Tent & Ventilation System

Capital Costs:

Tent Ventilation/Treatment System $500,000


Design (15%) $75,000


Reporting (15%) $75,000

Total Capital Costs: $850,000

Operation, Monitoring &Maintenance Costs (assume 90 days) $630,000



Additional Reporting (15%) $94,500

Total OM&M Cost: $976,500

TENT AND VENTILATION ALTERNATE TOTAL COST: $1,826,500


Note:


SHEET NO.



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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 4 PHYSICAL BARRIERS/LNAPLEXTRACTION LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.4.2JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONIC FILEPROVIDED BY DUPONT STREET DEVELOPERS, LLC, ENTITLED"ALTERNATIVE 4 PHYSICAL BARRIERS/LNAPL EXTRACTIONLAYOUT," DATED 3/29/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY






Page 4-64

Shoring may remain in place following the completion of excavation at locations adjacent to LNAPL impacts to mitigate the LNAPL that may remain outside of the excavation from reentering the remediated area and the potential off-site migration of LNAPL that remains on-site following remediation. The shoring system will be designed in consideration of which type wi ll adequately support the adjoining infrastructure the satisfaction of the NYCDOB, and may not provide a fully watertight barrier after remedy if it is left in place

Extraction and disposal of LNAPL remaining outside of the shoring would be conducted using a series of recovery wells located beneath the sidewalks adjoining the west and south sides of the Site. These wells would remove LNAPL from beneath the sidewalks and from portions of the adjoining Franklin and Dupont Streets. Proposed LNAPL recovery well locations are shown on Figure 4.1.4.2.

LNAPL extraction is also considered for three off-site areas, as shown on Figure 4.1.4.2. Extraction wells would be installed in the sidewalk area adjoining portions of the east and south sides of the Greenpoint Playground in and near the area where LNAPL is present (MW-25). Extraction would remove the LNAPL that is present near well MW-25 and reduce the amount of LNAPL present beneath Franklin Street and the Franklin/Dupont Street intersection over time.

An off-site physical barrier is also considered as part of this remedial alternative to prevent potential LNAPL migration onto the off-site property that is planned to be developed with a school. Monitoring will be necessary to assess the potential presence of LNAPL near the physical barrier. If LNAPL does migrate to the vicinity of the physical barrier, then LNAPL extraction and disposal would be required to remove the LNAPL in proximity to the barrier. Potential LNAPL recovery well locations are shown on Figure 4.1.4.2, should LNAPL recovery become necessary. As LNAPL has not been observed in any of the three existing monitoring wells located to the southwest of the Franklin Street/Dupont Street intersection, LNAPL extraction would not be implemented unless LNAPL is detected in any of these wells in the future.

LNAPL has been identified beneath the southeastern corner of the Franklin Street/Dupont Street intersection. Extraction and disposal of LNAPL from this location is considered to remove LNAPL from beneath the sidewalk and in proximity to the off-site properties in this area. LNAPL extraction wells for this area are shown on Figure 4.1.4.2.

LNAPL extraction may be accomplished using recovery wells and/or recovery trenches. As discussed in Section 4.1.2, the selection of recovery trenches or wells for each remedial area should be made following a full assessment of the implementation considerations at each location. For the purposes of this remedial alternative, it is assumed that closely-spaced recovery wells are used for LNAPL recovery. Similarly, it is assumed that the recovery equipment includes belt skimmers installed in the extraction wells due to the high viscosity of the LNAPL to be recovered. The removed LNAPL would be temporarily contained at each recovery location in a tank to be located in a subgrade vault. The LNAPL would be periodically removed from the tanks using a vacuum truck and transported for off-site disposal at an approved facility.

Page 4-65

It may be feasible to enhance LNAPL recovery via in-situ chemical treatments, such as surfactant injection that could enhance the mobility of the LNAPL, thereby improving its recovery rate. Typically, this type of treatment is conducted after recovery has been initiated and is often used as a "polishing" method. Bench testing would be required to initially evaluate whether the Site LNAPL is amenable to chemical treatment. If bench testing is successful, then in-situ pilot testing would be required to demonstrate this method in the field and obtain information necessary for design. Pilot testing will be considered following an assessment of the performance of the on-site recovery system. For this FS, an allowance has been made for bench testing. Costs for the LNAPL recovery wells under this Alternative have been estimated as shown on Table 4.1.4.2. Backup for these costs is provided in Appendix C. As the physical barrier costs have been included in the costs associated with the soil and LNAPL excavation and disposal, they are not included in Table 4.1.4.2. Please note that the costs have been estimated on a net present worth basis for 30-year, 15-year, and 10-year remedial periods. Based on previous experience with LNAPL recovery systems and the highly viscous nature of the LNAPL at this Site, it is anticipated that the system that will be designed for current conditions may reach the limits of its effectiveness within a few years of operation but (under this Alternative) will continue to be operated for up to 15 years to maximize LNAPL recovery. In response to a NYSDEC request, the cost for a 10-year remedial period is also provided for cost comparison between Alternatives.

Groundwater Air Sparging /Soil Vapor Extraction

Following the completion of the remedial excavation described above, there would remain some VOC-impacted soil on-site (below 16 feet) and off-site. AS is proposed to treat VOC-impacted soil below the water table on-site and to treat impacted groundwater and SVE is proposed to remove vapors resulting from AS. A site plan showing the potential layout of an AS/Thermal/SVE system is presented in Figure 4.1.4.3.

AS and SVE would be used to directly address groundwater VOC impacts identified on the northeastern portion of the Site and in the downgradient vicinity of the Site. AS would actively reduce VOC concentrations in the affected areas by enhancing volatilization of VOCs from the groundwater. The AS area includes the proximity of borings 3SB-9, 3SB-8, and 2SB-1/MW-34 (Figure 6 in Appendix A), all of which showed TCE-impacted soil to depths of at least 20 feet. The impacted soil at depth includes portions of the lower permeability clay/silt layer underlying the sand and gravel; AS will be used in this area to treat the impacted soils remaining at depth following excavation, as well as the impacted groundwater. The AS wells would be extended to the bottom of the impacted interval, which has not been completely defined but is known to extend to at least 20 feet in the targeted treatment area. Additional soil borings would be needed in this area during the remedial design phase to determine the depth of the AS wells. An SVE system would be used in the AS area to remove the volatilized VOCs from the subsurface for discharge to the atmosphere. SVE would also directly reduce VOC concentrations in the unsaturated zone soils in the off-site areas within their ROls. SVE will reduce the amount of VOCs in Site soil that have the potential to migrate to groundwater or soil vapor and would also directly remove soil vapors in the AS treatment area, thus providing SVI mitigation within the SVE ROls. Groundwater monitoring would be required to document the progress of remediation. Effluent monitoring would be performed to evaluate the reduction in VOC concentrations over time and to confirm that emissions from the SVE system meet regulatory requirements. The NYSDEC DAR-1 guidance document would be used to determine if effluent treatment is necessary.

Page 4-66


LNAPL OFF-SITE PHYSICAL BARRIER AND EXTRACTION/DISPOSAL


Cost (15 Years)

Capital Costs:

Extraction Wells Adjoining Site $428,800 $428,800


Contingency (15%) $64,300 $64,300


Reporting (15%) $64,300 $64,300

Capital Cost Subtotal (adjoining site): $728,900 $728,900

Off-site Wall and Extraction Wells $680,900 $680,900


Contingency (15%) $102,100 $102,100


Reporting (15%) $102,100 $102,100

Capital Cost Subtotal (offsite): $1,157,400 $1,157,400


Annual Operation, Monitoring and Maintenance Costs: $135,200 $135,200


Extraction System Replacement $164,500 $297,100



Note:


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ALTERNATIVE 4 AS/THERMAL/SVE SYSTEM LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.4.3JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


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1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "ALTERNATIVE 4 AS/THERMAL/SVE SYSTEMLAYOUT," DATED 3/29/16, ORIGINAL SCALE 1" = 60'.

LEGEND:



IHWDS BOUNDARY




PROPOSED THERMAL TREATMENT WELL


Page 4-68

The AS portion of the system would be designed to treat areas where significant groundwater VOC contamination has been observed on-site and in close downgradient and cross gradient proximity to the on-site VOC source area. The AS system would likely include four AS wells located on-site near the source area (see Figure 4.1.4.3); two of the AS wells would be positioned to treat groundwater beneath the sidewalk immediately north of this area. Most of the AS screens would be set at a depth of approximately 18 to 20 feet to treat groundwater situated in the more permeable stratigraphic intervals above the extensive clay/silt that underlies the area. At least one AS screen will be set at a depth below 20 feet to treat the deeper TCE-impacted soil. Based on previous experience with other AS systems in the NYC metro area, it is anticipated that an airflow of between 10 and 16 SCFM per well at a pressure of 20 to 40 pounds per square inch would be needed to result in an ROI of about 30 feet at each AS well. A compressor capable of a total flow of 60 to 80 SCFM at the targeted pressure is indicated.

SVE wells would be required to capture vapors resulting from AS treatment sparging. The SVE wells would also treat VOC-impacted soil that may be present in the unsaturated zone within their ROls and remove soil vapors associated with the VOC-impacted area. SVE system design will need to consider stratigraphic variation to maximize effectiveness. The SVE system would likely include five wells, including two wells beneath the sidewalk on the south side of Clay Street to provide for enhanced off-site treatment, one well centered on the area where TCE is present in deeper soil, and two wells along the eastern Site boundary to provide for additional soil treatment and vapor recovery. It is anticipated that an SVE ROI of about 50 feet may be achieved with a flow rate of about 100 SCFM under a vacuum of between 10 and 150 inches of water. The blower(s) would be appropriately sized for the anticipated total flow rate and vacuum of the SVE system. Sub-slab monitoring points would also be installed to just below the slab to allow for confirmation of the SVE ROI and to allow for sub-slab vapor sampling, as needed.

Costs for an AS /SVE system to treat the VOC source area have been estimated as shown on Table 4.1.4.3. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for both a 30-year remedial period and a four-year remedial period. Based on previous experience with AS/SVE systems, the AS/SVE system is anticipated to reach the limits of its effectiveness within about four years of operation.


Groundwater and LNAPL monitoring is considered as part of Remedial Alternative 4 to provide data needed to confirm that the identified groundwater impacts are being reduced by the active remedial methods. LNAPL would also be monitored to confirm that migration is not occurring, to document the anticipated reduction in LNAPL extent and apparent thickness in the off-site areas over time, and to confirm that LNAPL remains absent in the on-site remediation area. This alternative would not actively reduce groundwater contaminant concentrations or LNAPL, but would provide for assessment of the anticipated reduction in groundwater impacts and LNAPL extent and apparent thickness over time due to other factors, such as remediation of other affected media and ongoing natural processes.

Groundwater and LNAPL monitoring would be conducted at select wells downgradient, cross gradient, and upgradient of the Site. Figure 4.1.4.4 shows the proposed locations of groundwater monitoring wells (blue circles) and LNAPL monitoring wells (green circles) to be included in the monitoring networks. For reference,

Page 4-69

TABLE 4.1.4.3

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 AIR SPARGING/SOIL VAPOR EXTRACTION


Capital Costs - AS/SVE System



Contingency (15%) $21,800 $21,800


Reporting (15%) $21,800 $21,800

AS/SVE Capital Cost Subtotal $247,300 $247,300 AS/SVE Annual Operation, Monitoring, & Maintenance

Costs $65,300 $65,300

AS/SVE OM&M Net Present Worth $1,318,700 $250,100

AS/SVE System Removal $6,500 $14,000 TOTAL COST (Capital and OM&M Net Present

Worth) $1,572,500 $511,400 This table was developed from previous submissions performed by FPM Group

Notes:

Assumed interest rate is 5% and assumed inflation rate is 2%. All costs rounded to the nearest $100

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IHWDS BOUNDARY





PROPOSED GROUNDWATER MONITORINGWELL NETWORK




Page 4-71

the locations of the off-site LNAPL plume and the on-site excavation/removal area, the area of TCE-impacted groundwater, and proposed physical barrier and LNAPL extraction wells are also depicted on Figure 4.1.4.4. All the wells presently exist except for the wells that would be installed in the soil/LNAPL excavation area (to replace wells that would be removed during excavation) and two needed near the edges of the existing on-site LNAPL plume. Groundwater monitoring for most of the wells would be conducted semiannually (twice per year) and groundwater monitoring around the AS/SVE system (MW-3, MW-8, MW-13, MW-18, MW-34 replacement, MW-35, MW-39 and MW-40) would be conducted quarterly to assess the progress of remediation. LNAPL monitoring would be conducted monthly. The monitoring frequencies would remain unchanged until the NYSDEC approves a change in monitoring frequency.

Costs for groundwater/LNAPL monitoring have been estimated as shown on Table 4.1.4.4 and are presented on a projected net present worth basis over 30 years and over variable durations coordinated with the potential duration of remedial systems operations. Backup for the estimated costs for this alternative are included in Appendix C.

Sub-Slab Depressurization

SSDSs would be used to prevent potential impacts to indoor air quality that may occur due to SVI. Under Alternative 4 SSDSs are contemplated for off-site properties in proximity to the area where TCE-impacted soil vapors have been identified. These areas include the adjoining NuHart facility building to the east and the two off-site buildings on the north side of Clay Street (15 and 19 Clay Street) where the potential for SVI has been identified. The SSDSs would not significantly reduce VOC concentrations in the sub-slab soil vapor, but would significantly reduce the potential for migration of soil vapors into indoor air. SVI monitoring would be used in conjunction with the SSDS to confirm that SVI is not occurring. Additional monitoring points would be necessary to optimize the operation of the SSDSs.

As noted above, this Alternative assumes that significant remedial activities will be conducted prior to Site redevelopment, including extensive soil excavations for remediation and additional remedial measures to address VOC impacts. Although the use of the sub-grade portion of the new Site building is not established, it is likely that this crawlspace area would be used for remedial equipment and the overlying first floor would be used primarily for parking with no occupancy. Under this Alternative it is assumed that the remedial activities conducted prior to redevelopment will eliminate VOCs in on-site soil vapors and significantly reduce VOCs in off-site soil vapors. It is also assumed that the on-site subgrade area will include a concrete floor and be ventilated in accordance with New York City criteria for subgrade parking garages. Therefore, an SSDS is not planned for the Site. A vapor barrier would be installed on-site as needed for typical construction in an urban area.

SSDS construction for the off-site areas would require installation of lateral piping beneath the off-site building. The existing soil vapor data from the RI Report indicate that soil vapor impacts are present beneath the western-most portion of the adjoining off-site property to the east, but are not present beneath the eastern-most portion of this property. These data are supported by sub-slab soil vapor data obtained during the recent RI of Lot 57 of the NuHart property, which was conducted

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TABLE 4.1.4.4



Cost (6 and 15 Years)

Capital Costs:


Contingency (15%) $7,000 $7,000


Reporting (15%) $7,000 $7,000









Page 4-73

under the oversight of the New York City OER and documented that there were no detections of TCE or its breakdown products in any of the sub-slab soil vapor samples from beneath Lot 57. Additional soil vapor area will be obtained for the off-site NuHart property (the lots closest to the Site are e-designated) and assessed to determine the extent to which mitigation is required. However, for the purposes of this FS the existing data were used to develop a conceptual layout for the off-site SSDS.

SSDS construction would require installation of lateral piping and/or vertical piping connected to suction points beneath the off-site buildings. For the purposes of evaluating Alternative 4, it is assumed that lateral piping is installed beneath the new building contemplated for the adjoining NuHart facility building to the east and that vertical piping connected to suction points is installed for the two off-site buildings on the north side of Clay Street. It is also assumed that a vapor barrier would be installed beneath the adjoining NuHart facility to the east. It is also assumed that access is provided for installation of the off-site suction points. As the amount of piping to be installed is significant, pilot testing would be required to confirm the anticipated ROI of the SSDS lateral and suction points prior to design of the individual SSDS components and to assess the interaction between the SSDSs and the SVE remedial system that would be installed under this alternative. A potential layout of the SSDSs using laterals and vertical piping connected to suction points is shown on Figure 4.1.4.5 and considers the potential SVE layout and the extent of soil vapors extending beneath off-site properties. The actual design of the SSDSs would be developed during the remedial design phase.

Installation of SSDS laterals and the vapor barrier would be conducted during construction of the contemplated new building for the adjoining NuHart facility to the east. The lateral piping would be connected to a blower which would then discharge via a stack to the atmosphere; for the purposes of evaluating Alternative 4 it is assumed that one blower is used. The potential flow rate for the horizontally-piped SSDS would be approximately 100 standard cubic feet per minute at a vacuum of up to 20 inches of water per leg of the system. SSDS equipment would be housed in an enclosure within the building; the enclosure would be insulated to reduce noise, ventilated to control temperature, and equipped with typical automated monitoring equipment and alarm systems. The vapor barrier would be installed above the SSDS laterals in conjunction with installation of the new building slab and would extend under the entire area of the e-designated lots on the NuHart property. Vapor barrier design would be coordinated with design of the new building.

Installation of the suction points and associated vertical piping and blowers would be co nducted in coordination with each of the affected property owners and their tenants. It is anticipated that the vertical pipes for the suction points would each be connected to an in-line fan and the piping would discharge to the atmosphere above the building roofs. The potential flow rate for vertically-piped SSDSs would be approximately 100 standard cubic feet per minute at a vacuum of up to 10 inches of water. Alternatively, the suction points may be connected to the on-site SVE system via piping placed beneath Clay Street, although for the purposes of this FS it is assumed that the SSDSs are operated on a stand-alone basis.

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IHWDS BOUNDARY




PROPOSED SSDS SUCTION POINT


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SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER


Capital Costs

SSDS, Vapor Barrier, and Suction Point Installation $214,300 $214,300


Contingency (15%) $32,100 $32,100


Reporting (15%) $32,100 $32,100




SSDS and Suction Point Removal $13,000 $27,200



Notes:


Page 4-76

Costs for SSDS design, construction, and monitoring, including vapor barrier installation beneath the new building to be constructed on the adjoining former NuHart facility, have been estimated as shown on Table 4.1.4.5 and are presented on a projected net present worth basis over 30 years. It is possible that operation of other remedial systems, such as the SVE system and associated AS and thermal treatment systems, will reduce the soil vapor levels sufficiently such that SSDS operation is no longer necessary. Therefore, we have also projected SSDS costs over six years (two years beyond the anticipated completion of AS/SVE remediation, as discussed above). Backup for the estimated costs for this alternative are included in Appendix C.


Monitoring for soil vapors and potential SVI is considered as part of Remedial Alternative 4 to assess the anticipated improvement in soil vapor conditions over time due to remedial activities and confirm that soil vapor impacts present beneath the pavement/sidewalks of nearby off-site areas do not affect indoor air quality at occupied structures. The monitoring activities would not actively reduce VOC concentrations in the soil vapor, but would be used to evaluate potential exposure issues, to assess reductions in VOC concentrations in soil vapor that are anticipated result from other remedial measures, and to assess whether the SVI mitigation measures (described below) are effective.

Soil vapor/SVI monitoring would include installation of vapor implants through the new building slab that is anticipated to be present following Site redevelopment (including locations to the south and

west of the vapor source area, through sidewalks at several key locations, and through the slab of the targeted off-site building (adjacent NuHart facility) in the area where TCE vapors have been identified to monitor soil vapors over time. SVI monitoring would also include installation of vapor implants through the slabs of key off-site buildings (15 and 19 Clay Street) to allow for monitoring of sub-slab soil vapor and indoor air to be conducted periodically. SVI monitoring would include indoor air sampling at those locations where sub-slab implants are installed. SVI monitoring would require that building access for implant installation and sampling be obtained from the property owners and that access for indoor air sampling be obtained from building occupants. For the purposes of this FS it is assumed that access to off-site properties is obtained. Figure 4.1.4.5 (previously presented) shows the proposed locations of soil vapor monitoring points and SVI monitoring points at the Site and adjacent NuHart facility. SVI monitoring point locations for other off-site properties would be selected in consultation with the property owners.


Costs for soil vapor and SVI monitoring have been estimated as shown on Table 4.1.4.6 and are presented on a projected net present worth basis over 30 years and over a six -year period as soil

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TABLE 4.1.4.6

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 SOIL VAPOR/SVI MONITORING


Capital Costs:


Contingency (15%) $3,500 $3,500

Design (15%) $3,500 $3,500


Reporting (15%) $3,500 $3,500





TOTAL COST (Capital and OM&M Net Present Worth): $1,197,900 $387,900



Page 4-78

vapor conditions are anticipated to improve after the source soil is remediated via excavation/disposal and AS. A monitoring frequency of twice per year is assumed. Backup for the estimated costs for this alternative are included in Appendix C.

Implementation of ECs and iCs

Implementation of ECs and ICs would be used to control potential exposures to impacts for all media under Remedial Alternative 4. Specifically, soil impacts and/or LNAPL may remain present on-site and LNAPL will remain present off-site in areas where it cannot be reasonably accessed. Soil vapor and groundwater impacts will also remain present, but are anticipated to diminish over time. ECs and ICs considered include a cover system EC (building slab for the Site and existing sidewalks and road pavement for off-site areas) to provide protection from impacted soil and LNAPL, and ICs (Site and groundwater usage restrictions, and an SMP) to control Site use and potential on-site exposures to soil, soil vapor, LNAPL, and/or groundwater. Access to the off-site subsurface is presently controlled by an IC consisting of a street-opening permit process that is required for penetration of the existing EC (sidewalks/pavement). An additional IC will be needed to control potential exposures during off-site subsurface activities that are conducted to depths where Site-related LNAPL and associated impacted soil are present. The IC considered under this alternative is posting of an environmental notice for street-opening permits that may be requested in the area where Site-related subsurface impacts are present. Implementation and control of on-site ECs and ICs would be governed by an environmental easement for the Site. Implementation and control of off-site ECs and ICs would be governed by the existing street-opening permit process and an environmental notice.

Costs for the ICs and ECs, including implementation of an environmental easement, SMP, annual inspections and cover system repairs, certification and reporting, have been estimated as shown on Table 4.1.4.7 on a net present worth basis over an assumed 30-year monitoring period. Backup for the estimated costs for this alternative are included in Appendix C.

Comprehensive Remedial Alternative 4 was evaluated relative to thenine criteria as follows:

Threshold Criteria:

Overall protection of public health and the environment: This alternative actively addresses groundwater, soil, and soil vapor VOC impacts within the AS/SVE system ROls, provides for active protection from SVI (via the SSDSs) for areas where the potential for SVI exists, and provides for additional protection from SVI (vapor barrier) for the contemplated new building to be constructed on the adjoining property to the east. This alternative is also anticipated to indirectly reduce groundwater VOC impacts outside and downgradient of the AS ROI. Therefore, this alternative is considered protective of public health and the environment in that contaminants in groundwater, soil, and soil vapor will be reduced or eliminated. This alternative also actively reduces the amount of LNAPL on-site and off-site and controls potential LNAPL migration and is, therefore, protective of public health and the environment in that LNAPL will be considerably reduced and potential migration will be controlled. This alternative also provides a means of assessing the anticipated reduction of contaminant concentrations in soil, groundwater, and soil vapor, evaluating the extent and apparent thickness of LNAPL over time, and assessing potential exposures to soil vapor via SVI.

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TABLE 4.1.4.7

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4 IMPLEMENT ECS AND ICS


Capital Costs:









http://cert.net/

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Potential public exposures to residual impacted materials would be controlled and monitored via ECs and ICs, this alternative, once fully completed, is more protective than Alternative 1 (No Action), Alternative 2, or Alternative 3;

Compliance with SCGs: This alternative provides for compliance with SCGs for VOCs in soil, groundwater and soil vapor in the VOC treatment area, which encompasses nearly all the VOC-impacted area, as VOC concentrations are anticipated to be reduced to near or below the SCGs in and downgradient of the excavation/AS/ SVE treatment area. This alternative provides for compliance with SCGs relative to soil and LNAPL in the on-site area as impacted soil and LNAPL removal is anticipated to be largely complete. In the off-site areas, this alternative provides for partial compliance with SCGs relative to the LNAPL as the extent and apparent thickness of LNAPL are anticipated to be reduced over time and a physical barrier will be present to prevent off-site migration of any remaining on-site LNAPL. This alternative does not directly provide for compliance with groundwater SCGs for other constituents (SVOCs), but does provide a means for evaluating achievement of SCGs in groundwater due to remediation by other measures and ongoing attenuation processes. This alternative does not directly provide for compliance with SCGs in soil vapor outside of the VOC excavation/SVE treatment area, but it does provide for mitigation of SV1 concerns via implementation of SSDSs outside of the treatment area and vapor barriers for new construction in areas where vapors may remain present. This alternative also provides a means for assessing achievement of SCGs in soil vapor that may result from soil and groundwater remediation by excavation/AS/SVE, and for evaluating compliance with the SCGs for indoor air in occupied buildings. This alternative includes ECs and ICs to monitor and control potential exposures for those media where SCGs are not obtained, thereby assuring that the SCGs are not exceeded at potential exposure points;

Balancing Criteria:

Long-term effectiveness and permanence: The VOC contaminants in the groundwater, soil, and soil vapor within the excavation/AS/SVE areas would be actively and permanently reduced by this alternative, resulting in an effective and permanent long-term remedy for VOCs in this area. This alternative includes removal and off-site disposal of on-site impacted soil and LNAPL and off-site LNAPL over time, thus permanently reducing the amount of impacted soil and LNAPL in the subsurface. This alternative also provides for long-term control of potential migration of any LNAPL remaining in the on-site source area. Groundwater/LNAPL monitoring does not provide a long-term effective or permanent remedy for groundwater impacts or LNAPL, but it provides a means to document changes in groundwater quality and LNAPL extent and apparent thickness due to other remedial measures and attenuation processes. The SSDSs and vapor barriers do not significantly remedy soil vapor impacts; however, SSDS operation will gradually reduce soil vapor impacts within its ROI over time and both SSDSs and vapor barriers provide long-term effective protection from SVI. Soil vapor and SVI monitoring do not actively remedy soil vapor impacts. However, soil vapor and SVI monitoring do provide a means for documenting changes in soil vapor conditions and the potential for SVI due to other remedial measures and are a long -term effective means for assessing soil vapor conditions and the potential for SVI.

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Implementation of ECs and ICs will result in an effective long-term remedy from the standpoint of public health as the residual materials remaining after remediation is complete would be isolated from public contact by a cover, prohibition of groundwater usage, controls on Site usage, controls on off-site subsurface access, and an SMP to govern management of residual materials, Periodic inspection and certification would be required, resulting in an effective and permanent long-term remedy;

Reduction of toxicity, mobility, or volume: This alternative provides for a reduction of toxicity, mobility and volume of VOC contaminants in the groundwater, soil, and soil vapor within the excavation/AS/SVE areas. It also reduces the toxicity, mobility, and volume of impacted soil and LNAPL in the on-site area as these materials will be removed. This alternative also provides for a reduction of toxicity, mobility and volume of off-site LNAPL. It does not directly provide for a reduction of the toxicity, mobility, or volume of other groundwater contaminants, but does provide a means for evaluating reductions in other groundwater contaminants due to other remedial measures or attenuation processes. This alternative does not directly reduce the toxicity, mobility, or volume of soil vapor contaminants except within the SVE ROI, but it does provide a means to evaluate reductions in soil vapor contaminants due to other remedial measures. The mobility of soil vapor contaminants would be reduced via operation of the SSDSs, implementation of vapor barriers for new construction, and maintaining the cover EC using ICs;

Short-term impacts and effectiveness: The short-term adverse environmental impacts or human exposures would be variable during the activities associated with implementing the Alternative 4 remedial measures. The on-site soil excavation, LNAPL removal, and physical barrier placement are anticipated to be conducted with the Site building demolished. These activities will require a significant period of excavation and dewatering operations, which will likely be performed under and environmental enclosure, therefore, there will be significant impacts from construction-related noise and vehicle operations. Although it is anticipated that the excavation work would be conducted under an environmental enclosure so as to reduce the potential for odor impacts, if odor impacts occur then additional protective measures may be required (odor-control systems). In addition, all the removed soil and LNAPL would be transported by triaxle or tractor trailer through the surrounding neighborhood to reach the nearest major transportation route to the disposal facilities. This will require a significant amount of trucks per day (possibly up to 1500 trucks) through the surrounding neighborhood based on the estimated volume of 22,500 CY soil. Because of the high viscosity of LNAPL observed, the recovery of the LNAPL during dewatering would be limited. Dewatering activities may be adversely impacted if LNAPL enters any of the pump systems since most dewatering pumps are not capable of extracting fluids with a high viscosity. Short-term adverse environmental impacts or human exposures are anticipated to be minimal to moderate for the LNAPL recovery aspects of Alternative 4, which will include a period of construction with the associated noise and vehicle activities, and ongoing vehicle and hazardous waste transfer operations. The short-term adverse environmental impacts or human exposures are anticipated to be minimal for the AS/SVE remedial system, groundwater/LNAPL monitoring, soil vapor and SVI monitoring, vapor barriers and SSDSs. Most of the intrusive activities for system construction

Page 4-82

would be conducted on-site, although much of the off-site SSDS construction would, of necessity, take place inside the off-site buildings. For all remedial activities, an approved HASP and CAMP would be required for the remedial construction and monitoring work and PPE would be utilized by remedial workers to control exposures. CAMP monitoring results would be used to verify that short-term impacts are minimized and to trigger implementation of additional controls if needed. Potential exposures to VOC emissions will be monitored via SVE and SSDS effluent sampling and emissions controls will be used if necessary to ensure that emissions meet Air Guide 1 requirements. Short-term adverse environmental impacts or human exposures are not anticipated in association with implementing ECs and ICs. Following completion of remedial construction and associated cover replacement, there are not anticipated to be any human exposures as the remaining affected media will be covered and the cover would be monitored;

Implementability: There are anticipated to be significant technical limitations to implementing certain aspects of this alternative. For the on-site soil excavation and LNAPL removal, the excavation to at least 17 feet below grade with associated shoring (physical barrier placement), dewatering, LNAPL removal, and backfill placement, is anticipated to present considerable obstacles for implementation of the remedy, including soil and fluids management on-site, noise and odor control, and transportation issues. For the off-site recovery wells, it is anticipated that there will be a significant risk of encountering subsurface obstructions (utilities, old foundations, etc.). Because of the high viscosity of LNAPL observed under the current condition, dewatering operations and fluids management during excavation will pose a significant obstacle. The potential for LNAPL to become entrained in the dewatering pumps is a considerable risk that may potentially cause failure of the dewatering system. A sudden shutdown of the dewatering system would potentially cause a rapid normalization in the hydraulic gradient potentially altering the LNAPL plume. Dewatering is also necessary to reduce the water, LNAPL, and content of soils for disposal. If soils are wet, then more truck loads would be required. This would result in increased trucking and stress to the local traffic patterns as well as increased costs to the Owner. The implementability of chemical treatment of LNAPL (such as with surfactants) to increase its mobility and recovery would have to be demonstrated through bench and pilot testing.

Since readily-available AS/SVE, SSDS, and vapor barrier remedial and monitoring technologies would be utilized, much of the proposed monitoring network is already present, there is no groundwater usage, and groundwater, LNAPL, and soil vapor/SVI monitoring procedures have already been conducted under the NYSDEC-approved work plans, there do not appear to be significant technical limitations to these aspects of Alternative 4. Design of the AS and SVE systems will need to take stratigraphic variations into account. An SMP and an environmental easement would be required, both of which may be readily implemented. The existing street-opening permit process is anticipated to facilitate implementation of the off-site IC, which is anticipated to be posting of an environmental notice for street-opening permits in the Site vicinity. It is anticipated that this alternative would be implemented in stages, each of which may last between several months to over a year; the overall construction period for this alternative is anticipated to be several years;

Page 4-83

Cost-effectiveness: This alternative provides long-term and short-term effectiveness and results in significant reductions in toxicity, mobility, and volume for VOCs in groundwater, soil and soil vapor within the excavation/AS/SVE system areas. The AS/SVE system is also likely to indirectly reduce groundwater and soil vapor impacts outside of the ROI. The SSDSs and vapor barriers will also provide long-term and short-term effectiveness, but will not result in significant reductions in toxicity or volume of soil vapor VOCs (although mobi lity will be significantly reduced). This alternative also provides long-term and short-term effectiveness for LNAPL and impacted soil reductions on-site, off-site control of potential migration via the physical barrier, and results in reductions in toxicity, mobility, and volume for LNAPL in the areas where recovery wells are operated. Remedial design and implementation for the on-site soil excavation and LNAPL removal will be very high. Design, construction and operating costs for the off-site LNAPL removal will be moderate to high. AS/SVE remedial system and SSDS design, installation, operation, and monitoring costs are anticipated to be moderate, and the groundwater, LNAPL, soil vapor, and SVI monitoring and vapor barrier design and implementation costs are relatively low. Overall, the costs for this comprehensive alternative are high, proportionally, relative to its overall effectiveness. The cost-effectiveness for the remedial and monitoring components are increased somewhat when used in conjunction with the ECs/ICs that control potential exposures;

Land use: This alternative is protective of the reasonably-anticipated land use of the Site,

which is anticipated to be redeveloped with a restricted residential and/or commercial use, as impacted soil will be removed to 16 feet below grade, LNAPL will be removed, VOCs within the excavation/AS /SVE system areas would be remediated, an SSDS and vapor barrier would provide for mitigation of potential off-site SVI concerns, groundwater use is not occurring or contemplated, a cover will be installed over any residual impacted materials, and monitoring data would be available to assess LNAPL changes, groundwater quality, and potential SVI concerns on-site. This alternative is also protective of the current and reasonably-anticipated land use in the Site vicinity, as the AS/ SVE system is anticipated to reduce or eliminate off-site soil, groundwater and soil vapor VOC impacts and SSDSs would be installed to mitigate potential SVI concerns, potential migration of any remaining on-site LNAPL would be controlled, off-site LNAPL will be removed, groundwater use is not occurring, a cover will remain present over impacted materials, and monitoring data would be available to assess changes in the condition of subsurface media over time. Under this alternative, residual materials exceeding applicable SCGs would be isolated from the public via cover, controls on land use, and controls on groundwater use. These controls would be implemented on-site via an environmental easement and an SMP and off-site via the existing street-opening permit process and posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present;

Page 4-84

Modifying Criteria

Community Impact: The on-site remedy consists of full excavation and AS/SVE. This remedy will require the demolition of the existing building covering the Registry Site.

Traffic: This alternative is anticipated to significantly impact traffic during this timeframe. Traffic increases will stem from material deliveries, employees travelling to and from the Site, installation of engineering controls for the work (Support of Excavation, Environmental Enclosure, Dewatering Systems and Air Treatment Systems) and trucking for material export and material import. Due to the nature of the contamination and the location of the Site with respect to adjacent buildings, an environmental enclosure would encompass as much of the Registry Site footprint as possible. Due to the size of the Registry Site, it may be necessary to build the tent into two locations. During delivery, several double sized tractor trailers would be mobilized to the Site with loads of skins (tarping), purlins, gables and girts and structural steel to begin the erection process. In addition, a crane will be necessary to install portions of the structural frame. During mobilization and erection, it is likely that the remedial contractor will apply for permits to shut down Dupont Street in its entirety and one lane of Franklin street to facilitate the installation. Once the frame is installed, the skins of the environmental enclosure are required to be stretched out to slide them up the tracks in the structure. To accommodate this, the remedial contractor may elect to apply for permits to shut down Franklin Street for this operation. After erection, counterweights and anchors will need to be installed at the perimeter of the tent to secure it to the ground. Once secured, multiple air handling units will be necessary to transfer air to the environmental enclosure and collect and treat outgoing air. Air handlers typically are fueled by diesel gasoline. The air handling units are the approximately the size of a triaxle truck. During operation, it is anticipated the remedial contractor will apply for a sidewalk and lane closure on Franklin Street, Sidewalk and No Parking Restriction on Clay Street and Sidewalk and No Parking Restriction on Dupont Street.

Erection, Operation Installation of support of excavation and remedial excavation is anticipated to take over a year to complete which would be dependent on final designs. It is assumed that with potential lane closures and the significant amount of tractor trailers necessary to transport the hazardous waste from the Site that traffic in the immediate area of the Site would be significantly impacted. In addition to the immediate area, consideration should be made for major construction projects that are occurring along major routes in proximity to the Site such as the Kosciusczko Bridge Replacement project and other major development projects in the area. With the need for tractor trailers to remove the hazardous waste from the Site, required lane and parking restrictions for the operation of the environmental enclosure and the existing and forecasted construction in the area, this alternative would significantly increase congestion. In addition, project schedule may elongate due to the continued stress on the area traffic patterns.

Noise: This alternative will utilize heavy equipment to install the support of excavation, perform the excavation. This alternative will also utilize air handlers and dewatering elements that will run for Construction shift (and night if necessary). Remedial construction

Page 4-85

elements will provide a long-term impact on noise levels during installation and operation. In addition to the Site equipment, the significant truck traffic during the day will also increase the noise during the work shift.

Air Quality: This alternative is not anticipated to significantly impact air quality as most of the work will be performed under the environmental enclosure. It is noted that during the remedy, community air monitoring will be performed during all intrusive activities. All collected air from the air handling units and AS/SVE system will be treated to adhere to NYSDEC standards prior to discharge. Operation of the air handling units is anticipated during the day. When not in operation, there is potential for diffusion and migration of vapors from the containment structure. Increases in vehicular traffic have the potential to agitate existing sediments on roadways. The potential for a significant amount of trucking to come to and from the Site may potentially impact residents at the Senior Housin g Residencies on the South Side of Dupont Street if they have respiratory problems.

Aesthetics: This alternative requires demolition of the building and installation of a large environmental enclosure to accommodate the remedial construction. Multiple sidewalks, street parking and some lanes will be coordinated off with a combination of concrete and plastic barriers for the duration of the work. Outside of the environmental enclosure there will be multiple large air handling units and concrete anchors installed around the perimeter of the environmental enclosure for the duration of the excavation operation. There will be consistent vehicular traffic in and outside of the large environmental enclosure during the excavation. The increased vehicular activity, location of necessary equipment for operation of the environmental enclosure may detract the residents use of the public park across the street on Franklin Street. Based on the timeline of remediation, remedial activities will likely occur in the spring, summer and fall months.

The total estimated costs for implementing Remedial Alternative 4 are shown on Table 4.1.4.8.

Page 4-86

TABLE 4.1.4.8

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 4

Description Cost


Initial Capital Costs Soil and LNAPL Excavation and Disposal (Tent/Ventilate

Alt.) $15,768,400 ($1,826,500)

$15,768,400 ($1,826,500)

LNAPL Physical Barriers and Extraction/Disposal $1,886,300 $1,886,300 AS/SVE (TCE-impacted area) $247,300 $247,300 Groundwater/LNAPL Monitoring Network $72,400 $72,400 SSDSs and Vapor Barrier $364,200 $364,200 Soil Vapor/SVI Monitoring Network $39,600 $39,600 Implement ECs and ICs (environmental easement, SMP) $46,000 $46,000

Initial Capital Cost Subtotal: $18,424,200 ($1,826,500)

$18,424,200 ($1,826,500)

O&M Net Present Worth over Anticipated O&M Periods LNAPL Extraction (off-site, 10 years) $2,729,500 $1,187,900 AS/SVE (4 years) $1,318,700 $250,100 Groundwater/LNAPL Monitoring (6 and 10 years) $3,187,300 $1,168,700 SSDS (6 years) $1,578,700 $368,900 Soil Vapor/SVI monitoring (6 years) $1,142,300 $315,700 Certification and Reporting (30 years) $255,400 $255,400 O&M, Cert. and Reporting Net Present Worth

Subtotal: $10,211,900 $3,546,700

Post-Remedial Capital Costs LNAPL Extraction System Removal (10 years) $164,500 $297,100 AS/SVE Removal (4 years) $6,500 $14,000 Groundwater and LNAPL Monitoring Network

Replacement (10 years) $15,500 $24,200

SSDSs Removal (6 years) $13,000 $27,200 Soil Vapor/SVI Monitoring Network Abandonment (6

years) $16,000 $32,600


O&M/Certification/Reporting) $28,851,600 ($1,826,500)

$22,366,000 ($1,826,500)

This table was developed from previous submissions performed by FPM Group Note: Assumed interest rate is 5% and assumed inflation rate is 2%. All subtotal and total costs are rounded to the nearest $100.

Page 4-87

4.1.5 Alternative 5: Groundwater Cutoff Walls with LNAPL Extraction/Disposal, Targeted Excavation, In-Situ Thermal Treatment Followed with In-Situ Chemical Oxidation, Off-Site Physical Barrier, Air Sparging/Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization and Vapor Barrier, Soil Vapor/SVI Monitoring, and ECs/ICs.

This comprehensive remedial alternative would address identified impacts in each of the Site media with the objective of removing more contaminant mass than Alternative 3 in a shorter period, including mass reduction of the majority of the LNAPL plume, providing on-site containment of LNAPL, addressing the off-site LNAPL plume and providing protection from potential exposures for all media. ECs and ICs will continue to be necessary to implement this remedy, control potential exposures during remedial activities, and control potential exposures over the long term.

This alterative will consist of off-site LNAPL extraction using either high viscosity product pumps or belt skimmers to reduce LNAPL mass off Site under Franklin Street. In addition, a groundwater cutoff wall is proposed to protect the property designated as a proposed public school and prevent any migration of LNAPL onto this property. On-Site LNAPL will be addressed through TCH to enhance LNAPL recovery. The reduction of majority of the LNAPL plume (found primarily under the Site) will reduce any potential subsequent migration of LNAPL mass to off-Site locations. In addition, a groundwater cut off wall will be installed on the Site around the LNAPL mass to further reduce the potential for off-site migration and aid in the TCH enhanced recovery efforts. The TCH may also address a portion of the dissolved VOC plume at an overlap in the contaminant foot prints. AS/SVE will be used to address the remaining dissolved VOC and VOC impacted soils. Sub-Slab Depressurization, Vapor Barrier, Soil Vapor/SVI Monitoring, and ECs/ICs will be used to further protect the public and future occupants.

Specifically, the purpose of the remedy is to lower the viscosity of the LNAPL consisting of bis(2-ethylhexyl) phthalate (DEHP), Di-n-octyl phthalate and Hecla oil and thereby increase our ability to recover the LNAPL through groundwater / LNAPL extraction. Under current conditions, the plume is relatively stable and not moving more than 0.18 ft/year. Heating the subsurface to 100º C will lower the viscosity and facilitate more efficient recovery of LNAPL than under current conditions. The proposed remedy will utilize multi-phase extraction (water, LNAPL and steam/vapors.) This will result in hydraulic control the Site, removal of groundwater, removal of LNAPL and removal of vapors. In addition, the remedy will include a groundwater barrier wall around the Site to help maintain hydraulic control of the plume. As part of this remedy, engineering controls are proposed to mitigate potential for altering the current subsurface conditions so as to mobilize the plume. Based on the case studies and discussion with the industry experts, heating the subsurface to 100º C will not significantly cause mobilization of the off-site plume. The remedy proposed is a comprehensive approach that will contain measures that will continue to control the plume location.

In evaluating this remedial alternative, it is assumed that the current Site condition (vacant building) continues for a period following initial implementation of the remedy and that redevelopment following in-situ remedies includes partial excavation of the Site subsurface. However, partial excavation (removal of former tanks and associated LNAPL impacted soils and water) will occur prior to in-situ treatment. Redevelopment of the Site will not occur until completion of in-situ remediation within the Site.

Groundwater Cut-Off Wall with Off-site LNAPL Extraction/Disposal

Page 4-88

Two groundwater cut-off walls and off-site LNAPL extraction and disposal are considered as part of this Remedial Alternative to prevent potential LNAPL migration onto an off-site property (currently under consideration as a potential school) and between on-site and off-site areas, and to remove LNAPL from off-site areas. Monitoring will be necessary to confirm that LNAPL migration is not occurring and to document the removal of LNAPL over time; monitoring is discussed in the following section.

The first groundwater cut-off wall will encompass the majority of the on-site LNAPL plume that abuts Dupont and Franklin Street and will be placed around the footprint of much of the LNAPL source area, as described on Figure 4.1.5.1. This remedial strategy will prevent LNAPL that may remain outside of the cut-off walls from re-entering the remediated area, prevent off-site migration of LNAPL during the implementation of in-situ thermal conductive heating and prevent potential off-site migration of any residual LNAPL remaining on-site following in-situ remediation.

Extraction and disposal of LNAPL outside of the cut-off walls would be conducted using a series of recovery wells located beneath the sidewalks adjoining the west and south sides of the Site. These wells would remove LNAPL from beneath the sidewalks and from portions of the adjoining Franklin and Dupont Streets. Proposed LNAPL recovery well locations are shown on Figure 4.1.5.1.

LNAPL extraction is also considered for three off-site areas, as shown on Figure 4.1.5.1. Extraction wells would be installed in the sidewalk area adjoining portions of the east and south sides of the Greenpoint Playground in and near the area where LNAPL is present (MW-25). Extraction would remove the LNAPL that is present near well MW-25 and reduce over time the LNAPL present beneath Franklin Street and the Franklin/Dupont Street intersection. It is important to note that the results of the investigations conducted by FPM indicated that the LNAPL is viscous and relatively immobile with flow velocities of ~0.18 ft per year. This equates to a migration of 9 feet in 50 years. This allows for the use of conventional product recovery methods to be employed in the off-Site plume location. To further protect the proposed school property located to the southwest of the Site, across the Franklin Street/Dupont Street intersection, an off-site physical barrier (cutoff wall) is also considered as part of Remedial Alternative 5. LNAPL has not been identified in any of the monitoring locations adjoining this property, however it is possible that LNAPL migration could be triggered by future construction activities such as dewatering that alter subsurface conditions. Therefore, to prevent potential future exposure and reduce the potential impact to the environment, a physical barrier is considered for this location. Monitoring will be necessary to assess the potential presence of LNAPL near the physical barrier. If LNAPL does migrate to the vicinity of the physical barrier, then LNAPL extraction and disposal would be required to remove the LNAPL in proximity to the barrier. LNAPL extraction would not be implemented as part of the remedy unless LNAPL is detected in these wells in the future. Potential LNAPL recovery well locations are shown on Figure 4.1.5.1, should LNAPL recovery become necessary.

LNAPL has been identified beneath the southeastern corner of the Franklin Street/Dupont Street intersection. Extraction and disposal of LNAPL from this location is considered to remove LNAPL from beneath the sidewalk and in proximity to the off-site properties in this area. LNAPL extraction wells for this area are shown on Figure 4.1.5.1.

It may be feasible to enhance off site LNAPL recovery via in-situ chemical treatments, such as surfactant injection that could enhance the mobility of the LNAPL, thereby improving its recovery rate. Typically, this type of treatment is conducted after recovery has been initiated and is often used as a "polishing" method. Bench testing would be required to initially evaluate whether the Site LNAPL is amenable to chemical

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PROJ MGR:

DRAWN BY:


SCALE:


ALTERNATIVE 5 GROUNDWATER CUTOFFWALL/LNAPL EXTRACTION LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.5.1JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:


LEGEND:



IHWDS BOUNDARY





EXTENT OF GROUNDWATER CUTOFF WALL

EXTENT OF SOIL REMOVAL

Page 4-90

TABLE 4.1.5.1

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 LNAPL PHYSICAL BARRIER AND EXTRACTION/DISPOSAL


Capital Costs:

On-site Barrier Wall $443,500 $443,500

Off-site Barrier Wall $139,300 $139,300


Contingency (15%) $87,400 $87,400


Reporting (15%) $87,400 $87,400

Capital Cost Subtotal (Barrier Wall): $990,700 $990,700

Off-site Barrier and Extraction Wells $1,462,600 $1,462,600


Contingency (15%) $129,100 $129,100


Reporting (15%) $129,100 $129,100

Capital Cost Subtotal (off-site LNAPL Extraction): $2,065,000 $2,065,000


Annual Operation, Monitoring and Maintenance Costs:

$146,800 $146,800


Extraction Systems Removal $148,400 $267,800

TOTAL COST (Capital and OM&M Net Present Worth):

$5,566,400 $4,011,100


Page 4-91

treatment. If bench testing is successful, then in-situ pilot testing would be required to demonstrate this method in the field and obtain information necessary for design. For this FS, an allowance has been made for bench testing.

Costs for the cutoff walls and proposed LNAPL recovery wells under this Alternative have been estimated as shown on Table 4.1.5.1. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for a 30-year remedial period, a 2-year remedial period on-site, and an 8-year remedial period off-site. This remedial period also considers the enhanced removal of on-site source material contemplated under this alternative

Target Excavation, In-situ Thermal Conductive Heating and LNAPL Recovery Followed with In-Situ Chemical Oxidation

Target excavation would be performed in “hot spot” locations associated with the closed-in-place USTs, the piping trench systems (not shown on the figure) formerly used to store and convey phthalates and Hecla oil, and the area where VOC-impacted soils are present above the water table. The closed USTs and piping trench systems would be removed prior to initiation of the in-situ THC and the targeted soil would be removed during UST and trench removal. The vertical limit of soil removal in the targeted removal areas is estimated to be about 10 feet below grade. This limit was estimated based on the estimated depths of the USTs and underlying groundwater and may be changed during remedial activities based on visual observations. Excavation below the water table would not be conducted during targeted soil removal. After the hot spot excavation, the areas would be backfilled with certified clean backfill and a new concrete floor slab would be installed and tied into the existing concrete floor slab to restore a “thermal blanket” for the TCH remedy.

Under this alternative, the targeted removal work would be conducted inside the existing building prior to its demolition. However, if removal activities occur after the building is demolished it is possible that odor control may be necessary during removal of the USTs, piping systems, and associated soils, particularly as a measure of workers’ safety. Measures to monitor and, if necessary, control odors will be implemented during excavation activities. The control measures will include limiting the size of open excavations (particularly those excavations that include LNAPL-impacted soil), performing the excavations sequentially to limit the areas of exposed soil, use of odor-control foam on odorous excavation surfaces and excavated materials as needed, covering stockpiles and loaded trucks with tight-fitting covers, limiting stockpile sizes, and promptly loading and transporting removed materials. The existing building shell and odor control measures would serve as an environmental enclosure for protection of the public health and the environment during the excavation work. An in-situ thermal treatment system would be installed within the cutoff wall to enhance the mobility and recovery of LNAPL. Under this alternative, the building would be demolished following targeted excavation work and prior to installation of the TCH system. The in-situ thermal treatment consists of two sections: heating system and effluent collection/treatment systems. TCH would use heating elements spaced at approximate 15 foot intervals to heat the treatment area up to 100 degrees ºC (the boiling point of water). The increased temperature in the soils and groundwater would lead to an increase in vapor pressure, decrease in viscosity, increase in diffusion, and increased desorption, thereby substantially increasing the mobility and recovery of LNAPL, dissolved phase contaminants and absorbed phase contaminants. Multiphase vertical and horizontal extraction wells would be used

Page 4-92

to extract liquids, LNAPL, vaporized contaminants and steam to maintain pneumatic and hy draulic control. Alternatively, if the majority of LANPL is found in the sands and gravels and not within the silts and clays then steam enhanced recovery (SER) would be considered with a less dense heater spacing. The extracted liquid (liquids and condensate) would be treated with Granular Activated Carbon (GAC) and the extracted vapor would be treated with a Thermal Oxidizer, if necessary. The NYSDEC DAR-1 guidance document would be used to determine if effluent treatment is necessary. During the thermal treatment process, temperature and pressure would be monitored to track subsurface heating, pneumatic, and hydraulic control. All vapor and liquid effluent would be subject to air and water discharge limits under State and City regulations. If any contaminates are above the discharge limits in the effluent, then they will require treatment prior to discharge. The vapor and liquid treatment system would be monitored for mass removal and discharge compliance. Application of TCH or SER serves to shorten the LNAPL recovery timeframe and improve removal efficacy. The estimated remediation timeframe for LNAPL removal on-Site would be 1-2 years with off-Site removal times consistent with Alternative 3. Following the completion of thermal treatment and LNAPL recovery, In-Situ Chemical Oxidation (ISCO) will be applied to address residual contamination in groundwater beneath the Site. The targeted LNAPL on the site is mainly composed of DEHP DOP and Hecla Oil. For this FS, it is estimated that total volume of LNAPL is about 190,000 lbs. This is based on a treatment volume of 7,089 CY and an average concentration of approximately 9,316 mg/kg for DEHP and 1,750 µg/L for DOP. Remediation goals for this site consist of significantly reducing LNAPL mass both on and off-Site. The remaining Phthalate would be treated with ISCO through well injection. Selection and design of the in-situ chemical treatment would be made during the remedial design process. For this FS, an allowance for this enhancement of groundwater treatment has been made in the cost estimate followed thermal treatment.

Although it is assumed that additional Site soil may be removed for redevelopment purposes under this Alternative, for the purposes of this FS, this additional soil removal is not considered to be part of the remedial activity. It is assumed that the redevelopment soil removal would be conducted under the Site Management Plan (SMP) that would be an IC for this Site (see discussion below). Soil removal under the SMP would include screening by an environmental professional and appropriate management, including removal and disposal. Although this soil will likely include historic fill, for this purposes of this FS it is assumed that this soil is not removed for remedial purposes and, therefore, the associated costs are not included in this FS.

TCH followed by ISCO would directly address the LNAPL in the groundwater and impacted soil on the Site and would also indirectly address the SVOCs and VOCs in the northwest area. The estimated areas of in-situ thermal treatment followed by ISCO to remove the targeted LNAPL beneath the Site are shown on Figure 4.1.5.2 and Figure 4.1.5.3 and encompass the areas associated within the groundwater cutoff wall/TCH area addressing residual phthalate and TCE contamination.

Costs for the target hot spot excavation, in-situ thermal treatment followed with in-situ chemical oxidation alternative have been estimated as shown on Table 4.1.5.2 and Table 4.1.5.3. Backup for these costs are provided in Appendix C. Please note that these costs include capital costs for targeted soil

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PROJ MGR:

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SCALE:


ALTERNATIVE 5 IN-SITU THERMALTREATMENT/CHEMICAL OXIDATION

SYSTEM LAYOUT


AUGUST 2016 12.0076485.00

FIGURE

4.1.5.2JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


LEGEND:



IHWDS BOUNDARY




NOTES:



GROUNDWATER CUTOFF WALL

HEATER BORING

MULTIPHASE EXTRACTION WELL

HORIZONTAL EXTRACTION WELL

6 ft. BUFFER ZONE FOR UTILITY PROTECTION

8 ft. MINIMUM BUFFER ZONE FOR TEMPERATUREAND PRESSURE MONITORING

Horizontal Vapor Extraction Wells

Sheet Pile Wall

Multiphase Extraction Wells

TCH boring

Water SurfaceApproximate Depth

±12 ft. bgs

Treatment Area 1Treatment Depth

12-17 ft. bgs5.44 ft. of Thickness

* 5 ft heater stick up and down

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PROJ MGR:

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ALTERNATIVE 5 CONCEPTUAL DESIGN OFTHERMAL CONDUCTIVE HEATING (TCH)


AUGUST 2016 12.0076485.00

FIGURE

4.1.5.3JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


NOTES:

1. THE BASE MAP WAS DEVELOPED FROM AN ELECTRONICFILE PROVIDED BY DUPONT STREET DEVELOPERS, LLC,ENTITLED "CONCEPTUAL CROSS SECTION SW1-NE1,"DATED 3/24/16, ORIGINAL SCALE 1" = 50'.

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TABLE 4.1.5.2

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 THERMAL CONDUCTIVE HEATING (TCH) WITH

IN-SITU CHEMICAL OXIDATION

Description Cost

Capital Costs:

Installation Operation and Removal of TCH System $2,129,600

Installation, Operation and Removal of Chemical Oxidation System $210,000

Subtotal $2,339,600




Reporting (15%) $350,900

TOTAL COST: $3,977,200


Page 4-96


TARGETED SOIL EXCAVATION/DISPOSAL

Description Cost

Capital Costs:

Excavate/Dispose/Confirmatory Sampling/Treatment $323,600




Reporting (15%) $48,500



Page 4-97

removal, TCH, and an allowance for in-situ chemical oxidation only. Costs for additional measures (ECs and ICs) that may be needed to address residual soil contamination that is not removed by excavation and in-situ treatment are addressed below.

Air Sparqinq/Soil Vapor Extraction

Under Alternative 5, AS and SVE would be used to directly address soil and groundwater VOC impacts identified on the northeastern portion of the Site (outside the groundwater cutoff wall) and in the downgradient vicinity of the Site, like the AS/SVE system contemplated under Alternative 3. VOCs within the groundwater cutoff wall would be addressed though the TCH system. This alternative would actively reduce VOC concentrations in the affected areas by enhancing volatilization of VOCs from the groundwater. An SVE system would be used in the AS areas to remove the volatilized VOCs from the subsurface and directly reduce soil vapor impacts. Groundwater and soil vapor monitoring would be required to document the progress of remediation. Under this Alternative it is anticipated that AS/SVE would be implemented prior to redevelopment of the Site such that VOC impacts on-site and off-site may be reduced or eliminated early in the remedial process. Residual impacts that may remain present at the time of redevelopment would be further reduced or eliminated through is situ chemical oxidation, as described above.

This alternative would actively reduce VOC concentrations in the affected soil and groundwater by enhancing volatilization of VOCs, which would be captured by the SVE system, removed from the subsurface, and discharged to the atmosphere. In addition, proposed TCH system would overlap with a portion of the VOC contaminant area and further promote desorption and recovery of VOCs. SVE would also directly reduce VOC concentrations in unsaturated zone soils and soil vapor in the on-site and off-site areas within its ROI. Effluent monitoring would be performed to evaluate the reduction in VOC concentrations over time and to confirm that emissions from the SVE system meet regulatory requirements. The NYSDEC DAR-1 guidance document would be used to determine if effluent treatment is necessary. SVE will reduce the mass of VOCs in Site soil that have the potential to migrate to groundwater or soil vapor and would also directly remove soil vapors in the SVE treatment area, thus providing SVI mitigation within the SVE ROI.

A site plan showing the potential layout of an AS/SVE system is presented in Figure 4.1.5.4; this layout is the same as for Remedial Alternative 3. The AS portion of the system would be designed to treat areas where significant groundwater VOC contamination has been observed on-site and in close downgradient and cross gradient proximity to the on-site VOC source area. The AS system would likely include four AS wells located on-site near the source area; two of the AS wells would be positioned to treat groundwater beneath the sidewalk immediately north of this area. The AS screens would be set at a depth of approximately 18 to 20 feet to treat groundwater situated in the more permeable stratigraphic intervals above the extensive clay/silt that underlies the area. Based on previous experience with other AS systems in the NYC metro area, it is anticipated that an airflow of between 10 and 16 SCFM per well at a pressure of 20 to 40 pounds per square inch would be needed to result in an ROI of about 30 feet at each AS well. A compressor capable of a total flow of 60 to 80 SCFM at the targeted pressure is planned.

SVE wells would be required to capture vapors resulting from sparging and would likely include three wells centered on the AS area. SVE system design would take stratigraphic variations

Page 4-98

into consideration to maximize effectiveness. It is anticipated that an SVE ROI of about 50 feet may be achieved with a flow rate of about 100 SCFM under a vacuum of between 10 and 150 inches of water. The blower(s) would be appropriately sized for the anticipated total flow rate and vacuum of the SVE system. Sub-slab monitoring points would also be installed to just below the slab to allow for confirmation of the SVE ROl and to allow for sub-slab vapor sampling, as needed.

Costs for an AS/SVE system to treat the VOC source area have been estimated as shown on Table 4.1.5.4. Backup for these costs is provided in Appendix C. Please note that the costs have been estimated on a net present worth basis for both a 30-year remedial period and two to three years of remedial period. Based on previous experience with AS/SVE systems, the AS/SVE system is anticipated to reach the limits of its effectiveness within about four years of operation.


Groundwater and LNAPL monitoring is considered as part of Remedial Alternative 5 to provide the data needed to confirm that the identified groundwater impacts are being reduced by the active remedial methods. LNAPL would also be monitored to confirm that migration is not occurring and to document the anticipated reduction in LNAPL extent and apparent thickness in the on-site and off-site areas over time. This alternative would not actively reduce groundwater contaminant concentrations or LNAPL, but would provide for assessment of the anticipated reduction in groundwater impacts and LNAPL extent and apparent thickness over time due to other factors, such as remediation of other affected media and ongoing natural processes.

Groundwater and LNAPL monitoring would be conducted at select wells downgradient, cross gradient, and upgradient of the Site. Figure 4.1.5.5 shows the proposed locations of groundwater monitoring wells (blue circles) and LNAPL monitoring wells (green circles) to be included in the monitoring networks. For reference, the locations of the off-site LNAPL plume, the area of TCE-impacted groundwater, and proposed physical barrier and LNAPL extraction wells are also depicted on Figure 4.1.5.5. All the wells presently exist except for two wells that would be needed near the edges of the existing on-site LNAPL plume. It is anticipated that some of the wells may require replacement following excavations for redevelopment; costs for well replacement are included in this alternative. Groundwater monitoring for most of the wells would be conducted semiannually (twice per year) and groundwater monitoring around the AS/SVE system (MW-3, MW-8, MW-13, MW-18, MW-34, MW-35, MW-39 and MW-40) would be conducted quarterly to assess the progress of remediation. LNAPL monitoring would be conducted monthly. The monitoring frequencies would remain unchanged until the NYSDEC approves a change in monitoring frequency.

Costs for groundwater/LNAPL monitoring have been estimated as shown on Table 4.1,5.5 and are presented on a projected net present worth basis over 30 years and over variable durations coordinated with the potential duration of remedial systems operations. Backup for the estimated costs for this alternative are included in Appendix C.

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4.1.5.4JB

ZS

ZS

MT

JB

1" = 60'

N

0 30 60 120


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IHWDS BOUNDARY




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TABLE 4.1.5.4

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 5 AIR SPARGING/SOIL VAPOR EXTRACTION


Capital Costs



Contingency (15%) $16,200 $16,200


Reporting (15%) $16,200 $16,200




ASISVE System Removal $6,900 $14,800


Notes:


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4.1.5.5JB

ZS

ZS

MT

JB

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N

0 30 60 120


NOTES:


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IHWDS BOUNDARY








Page 4-102

TABLE 4.1.5.5



Capital Costs:


Engineering Design (15%) $3,200 $3,200

Contingency (15%) $3,200 $3,200


Reporting (15%) $3,200 $3,200

Total Capital Cost: $36,600 $36,600 Annual GW Monitoring and

Reporting Costs: $81,300 $81,300


OM&M Net Present Worth $3,187,300 $1,126,500 Monitoring Network

Abandonment $19,500 $35,200



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Sub-Slab Depressurization and Vapor Barrier

A sub-slab depressurization system (SSDS) and vapor barrier would be used to prevent potential impacts to indoor air quality in occupied buildings that may occur due to SVI. Under Alternative 5 an SSDS with a vapor barrier is contemplated for the portion of the off-site property (adjoining NuHart facility building to the east) beneath which TCE-impacted soil vapors have been identified and the potential for SVI has been documented. If SVI is identified, installation of an SSDS would be retrofitted into the existing building on the northern side of Clay Street located at 48 commercial Street, 15 Clay Street, and 19 Clay Street, which are located above the TCE plume. The SSDS would be a series of suction points and above ground lateral piping that would be installed directly into the slab. The SSDS and vapor barrier would not significantly reduce VOC concentrations in the sub-slab soil vapor, but would significantly reduce the potential for migration of soil vapors into indoor air. SVI monitoring would be used in conjunction with the SSDS and vapor barrier to confirm that SVI is not occurring. Additional monitoring points would be necessary to optimize the operation of the SSDS.

As noted above, this Alternative assumes that some remedial activities (such as implementation of AS/SVE) will be conducted prior to Site redevelopment. Although the use of the sub-grade portion of the new Site building is not established, it is likely that this crawlspace area would be used for remedial equipment and the overlying first floor would be used primarily for parking. Under this Alternative it is assumed that the remedial activities conducted prior to redevelopment will significantly reduce VOCs in on-site and off-site soil vapors and that the on-site subgrade area will include a concrete floor and be ventilated in accordance with New York City criteria for subgrade parking garages. Therefore, an SSDS is not planned for the Site. A vapor barrier would be installed on-site as needed for typical construction in an urban area.

SSDS construction may require extension to the off-site buildings. The existing soil vapor data from the RI Report indicate that soil vapor impacts are present beneath the western-most portion of the adjoining off-site property to the east, but are not present beneath the eastern-most portion of this property. These data are supported by sub-slab soil vapor data obtained during the recent RI of Lot 57 of the NuHart property, which was conducted under the oversight of the New York City Office of Environmental Remediation (OER). This investigation documented that there were no detections of TCE or its breakdown products in any of the sub-slab soil vapor samples from beneath Lot 57. Additional soil vapor will be obtained for the off-site NuHart property (the lots closest to the Site are e-designated) and assessed to determine the extent to which mitigation is required. However, for the purposes of this FS the existing data were used to develop a conceptual layout for the off-site SSDS.

For evaluating Alternative 5, it is assumed that lateral piping (and an associated vapor barrier) is installed beneath the new building to be constructed on the adjoining NuHart facility to the east and the building on the northeast area. In addition to this area, SSDSs will be implemented to mitigate SVI for the off-site buildings on the north side of Clay Street (15 and 19 Clay Street) in proximity to the area where TCE-impacted soil vapor has been identified if SVI is confirmed (via monitoring) to be occurring. For this option it is assumed that access is provided for monitoring and for SSDS suction point installation. Potential SSDS suction point locations on the north side of Clay Street are shown on Figure 4.1.5.6. As the amount of piping to be installed is significant, pilot testing would be required to confirm the anticipated ROI of the SSDS laterals prior to design of the individual SSDS components

Page 4-104

and to assess the interaction between the SSDSs and the SVE remedial system that would be installed under this alternative. A potential layout of the SSDS laterals is shown on Figure 4.1.5.6 and considers the potential SVE layout and the documented extent of soil vapors extending beneath the off-site property. The actual design of the SSDS would be developed during the remedial design phase and would incorporate any additional soil vapor data obtained from the NuHart property.

Installation of SSDS laterals and a vapor barrier would be conducted during construction of a new building on the adjoining former NuHart facility to the east. The vapor barrier would be placed above the SSDS laterals and beneath the slab and would extend under the entire area of the e-designated lots on the NuHart property. The lateral piping would be connected to one or more blowers which would then discharge via a stack to the atmosphere; for the purposes of evaluating Alternative 5 it is assumed that one or two blowers are used. The potential flow rates for the horizontally-piped SSDS would be approximately 100 standard cubic feet per minute at a vacuum of up to 20 inches of water per leg of the system. SSDS equipment would be housed in an enclosure within the building; the enclosure would be insulated to reduce noise, ventilated to control temperature, and equipped with typical automated monitoring equipment and alarm systems.

Costs for SSDS design, construction, and monitoring, including contingency costs for SVI mitigation on the north side of Clay Street, have been estimated as shown on Table 4.1.5.6 and are presented on a projected net present worth basis over 30 years. Backup for the estimated costs for this alternative are included in Appendix C.


Monitoring for soil vapors and potential SVI is considered as part of Remedial Alternative 5 to confirm that soil vapor impacts present beneath the pavement/sidewalks of nearby off-site areas do not affect indoor air quality at occupied structures and assess the anticipated improvement in soil vapor conditions over time due to remedial activities. The monitoring activities would not actively reduce VOC concentrations in the soil vapor, but would be used to evaluate potential exposure issues, to assess reductions in VOC concentrations in soil vapor that are anticipated result from other remedial measures, and to assess whether the SVI mitigation measures (described below) are effective.

Soil vapor/SVI monitoring would include installation of vapor sampling ports through the existing Site building slab, through nearby sidewalks at several key locations, and through the slab of the targeted off-site building (adjacent NuHart facility) in the area where TCE vapors have been identified to monitor soil vapors over time. SVI monitoring would also include installation of Vapor sampling ports through the slabs of key off-site buildings (15 and 19 Clay Street) to allow for monitoring of sub-slab soil vapor and indoor air to be conducted periodically. SVI monitoring would require that building access for implant installation and sampling be obtained from the off-site property owners and that access for indoor air sampling be obtained from building occupants . For the purposes of this FS it is assumed that access to off-site properties is obtained. Figure 4.1.5.5 (previously presented) shows the proposed locations of the soil vapor monitoring points and SVI monitoring points at the adjacent NuHart facility. SVl monitoring point locations for the other off-site properties would be selected in consultation with off-site property owners.

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N

0 30 60 120


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IHWDS BOUNDARY





POTENTIAL SUCTION POINT

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TABLE 4.1.5.6

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVE 3 SUB-SLAB DEPRESSURIZATION AND VAPOR BARRIER


Capital Costs

SSDS and Vapor Barrier Installation $214,300 $214,300


Contingency (15%) $32,100 $32,100


Reporting (15%) $32,100 $32,100




SSDS Removal $13,000 $26,400


Notes:


Page 4-107


Costs for soil vapor and SVI monitoring have been estimated as shown on Table 4.1.5.7 and are presented on a projected net present worth basis over 30 years and over a six-year period as soil vapor conditions are anticipated to improve after the source soil is remediated via AS/SVE. A monitoring frequency of twice per year is assumed. Backup for the estimated costs for this alternative are included in Appendix C.


Implementation of ECs and ICs would be used to control potential exposures to impacts for all media under Remedial Alternative 5. Specifically, soil impacts and LNAPL will remain present on-site and LNAPL will remain present off-site in areas, although these will decrease over time. Soil vapor and groundwater impacts may also remain present, but are anticipated to diminish over time. ECs and ICs considered include a cover system EC (building slab for the Site and existing sidewalks and road pavement for off-site areas) to provide protection from impacted soil and LNAPL, and ICs (Site and groundwater usage restrictions, and an SMP) to control Site use and potential on-site exposures to soil, soil vapor, LNAPL, and/or groundwater. Access to the off-site subsurface is presently controlled by an IC consisting of a street-opening permit process that is required for penetration of the existing EC (sidewalks/pavement). An additional IC will be needed to control potential exposures during off-site subsurface activities that are conducted to depths where Site-related LNAPL and associated impacted soil are present. The IC considered under this alternative is posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present.


Costs for the ICs and ECs, including implementation of an environmental easement, SMP, annual inspections and cover system repairs, certification and reporting, have been estimated as shown on Table 4.1.5.8 on a net present worth basis over an assumed 30- year monitoring period. Backup for the estimated costs for this alternative are included in Appendix C.

Comprehensive Remedial Alternative 5 was evaluated relative to the nine criteria as follows:

Page 4-108




Cost (6 Years)

Capital Costs:


Contingency (15%) $3,500 $3,500

Design (15%) $3,500 $3,500


Reporting (15%) $3,500 $3,500





TOTAL COST (Capital and OM&M Net Present Worth): $1,028,400 $341,100


Page 4-109


IMPLEMENT ECS AND ICS


Capital Costs:







Note:


http://cert.net/

Page 4-110

Threshold Criteria:

Overall protection of public health and the environment: This alternative actively addresses groundwater, soil, and soil vapor VOC impacts within the AS/SVE system ROls, provides active protection from SVI (via the SSDS) for the off-site area where the potential for SVI is documented, and provides for additional protection from SVI (vapor barrier) for the potential new building to be constructed on the adjoining property to the east. This alternative is also anticipated to indirectly reduce groundwater VOC impacts outside and downgradient of the AS ROI. Therefore, this alternative is considered protective of public health and the environment in that contaminants in groundwater, soil, and soil vapor will be reduced or eliminated. This alternative also actively reduces the mass of LNAPL on-site and off-site and controls potential LNAPL migration and is, therefore, protective of public health and the environment in that LNAPL will be considerably reduced and potential off-site migration controlled. It is anticipated that LNAPL will be removed from the within the Site via TCH enhanced recovery and ISCO. This alternative also provides a means of assessing the anticipated reduction of contaminant concentrations in soil, groundwater, and soil vapor, evaluating the extent and apparent thickness of LNAPL over time, and assessing potential exposures to soil vapor via SVI. Potential public exposures to residual impacted materials would be controlled and monitored via ECs and ICs. This alternative, once fully completed, is more protective than Alternative 1 (No Action), Alternative 2 and Alternative 3, and is similarly protective as Alternative 4 in the long term.

Compliance with SCGs: This alternative provides for compliance with SCGs for VOCs in soil, groundwater and soil vapor in the VOC treatment area, which encompasses most of the VOC-impacted area, as VOC concentrations are anticipated to be reduced to near or below the SCGs within and downgradient of this remedial area. This alternative provides for compliance with SCGs relative to LNAPL in the on-site and off-site areas as the majority of the LNAPL plume in the source area will be significantly decreased in mass via in-situ TCH and enhanced LNAPL recovery followed by chemical oxidation, potential off-site migration will be controlled, and the extent and apparent thickness of off-site LNAPL are anticipated to be reduced over time and a physical barrier will be present to prevent off-site migration of any remaining on-site LNAPL. This alternative does provide a means for evaluating achievement of SCGs in groundwater due to remediation by other measures and ongoing attenuation processes. In order to further evaluate compliance with SCG we evaluated the following: 1) potential to increase solubility and mobilize phthalate, 2) Potential to increase soil vapor generation and/or migration, 3) Potential to alter groundwater flow paths and mobilize LNAPL or VOC plume. 1) Phthalate esters are liquids at typical environmental temperatures. Melting points for these esters

are between 5.5°C and -58°C, and boiling points are between 230 and 486°C (Staples et al., 1997; Cousins et al., 2003). Stanley et al., (2003) established that the water solubility of the alkyl phthalate ester generally varies inversely with the length of the alkyl side chain. Dimethyl phthalate (DMP) is the most hydrophilic and water soluble of the esters. The C 10, C 11, and C 13 esters are the most hydrophobic and least water soluble (<0.001 mg/L). The solubility of phthalates does increase with temperature (Rose et al., 2012), However, so does decomposition via hydrolysis (Huang et al., 2013). Even if phthalate solubility increases, this will increase the recovery efficiency. The remedy includes a multiphase extraction system that will remove water, LNAPL, steam and vapor. The system will be designed to dewater under the Site, thus recovering

Page 4-111

dissolved phthalates as well as NAPL. As a further protective measure, the remedy will include a groundwater cutoff wall around the registry Site. The wall will be installed into the silty clay unit to further prevent migration of dissolved phase or LNAPL out from under the registry Site. To decrease the thermal effects on the LNAPL not contained within the proposed cutoff wall, the thermal electrodes wells will be installed at a minimum of 5’ away from the property line and temperatures will be monitored both outside and inside the cutoff wall to keep temperatures low under the sidewalks where utilities are located. Therefore, we do not anticipate any significant increases in dissolved concentrations or significant decreases in viscosities outside the cutoff wall. We will also have an LNAPL recovery system in place outside the cutoff wall to further control the LNAPL plume.

2) To control soil vapor generation and / or migration, the remedy has been designed to recover steam and vapors through vapor extraction wells. This will result in a negative pressure condition underneath the slab of the building in the extraction area. The existing slab will continue to function as an engineering control; voids or deficiencies in the slab will be repaired to maintain a thermal blanket. Continued maintenance of the slab (thermal blanket) along with the cutoff wall and the multi-phase extraction are designed to control any vapors generated from the remedy. All steam generated and collected during the remedy will be separated and treated with Thermal Oxidizer followed by granular activated carbon (GAC). Monitoring well networks will be installed on-site and off-site to monitor subsurface temperatures and pressure of areas outside the cutoff wall. Based on the thermal properties of the subsurface and the previous experience, maximum of 20 to 25 °C degree temperature increase will be observed outside the treatment area without a cutoff wall. The installation of a groundwater cut off wall will reduce any significant heating outside the treatment area and therefore no increase in volatilization is expected outside the treatment area.

3) We modeled the hydraulic conditions before and after the application of the cutoff wall. Please note that the modeling was done generically, without detailed calibration and sensitivity testing, and does not reflect consideration of site-specific hydrogeology or other influential hydraulic features. A further modeling will be during the design phase. Groundwater flow simulations were performed using the finite-difference model MODFLOW-2000 (referred to herein generically as MODFLOW)1. The numerical grid was discretized into 352 rows and 207 columns using variable spacing in the lateral dimensions with refinement in the primary area of interest (i.e., the proposed treatment cell). Approximate cell dimensions ranged from a maximum of 20 feet by 20 feet at the periphery of the model domain to 10 feet by 10 feet in the primary area of interest. In the vertical dimension, model layers 1, 2, and 3 were assigned thickness of 25, 10, and 5 feet, respectively, based on approximate and general dimensions of key strata encountered near the Site. The numerical grid was rotated approximately 7.5 degrees off normal to align the rows and columns with the orientation of the proposed cutoff wall. The entire model domain contained 218,592 cells with an active volume consisting of 157,092 cells with varying dimensions. Both scenarios were simulated using MODFLOW-2000 under steady-state flow conditions.

1 Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G., 2000, MODFLOW-2000, the U.S. Geological Survey modular

ground-water model -- User guide to modularization concepts and the Ground-Water Flow Process: U.S. Geological Survey Open-File Report 00-92, 121 p.

Page 4-112

(a) Hypothetical groundwater flow condition before the application of the cutoff wall and thermal treatment.

(b) Hypothetical groundwater flow condition after the application of the cutoff wall and thermal treatment.

Two scenarios were simulated using this model:

Groundwater flow under ambient conditions (i.e., without the proposed cutoff walls); and Groundwater flow under proposed conditions (i.e., cutoff wall scenario).

Page 4-113

Hydraulic properties were generally assigned for the key strata observed below the Site as follows:

Sand and gravel: horizontal hydraulic conductivity (Kh) of 75 feet per day; horizontal-to-vertical anisotropy ratio (Aniso) of 3:1

Silt/sand: Kh of 1.0 feet per day; Aniso of 3:1 Clay/silt: Kh of 0.001 feet per day; Aniso of 100:1

In general, model layers 1 and 2 were assigned properties associated with the Silt/sand stratum aside from an estimated area beneath the Site where sand and gravel deposits have been observed. Model layer 3 was uniformly assigned properties associated with the clay/silt deposits.

Boundary conditions and sources/sinks of groundwater were approximated to generate flow conditions that reasonably replicate observed groundwater elevations near the Site. For boundary conditions, constant head boundaries were specified along the East River and Newtown Creek via the MODFLOW time-varying constant head (CHD) package, and a no-flow boundary was specified along the southern extent of the model. For groundwater sources/sinks, areal recharge was applied to the model domain via the MODFLOW recharge (RCH) package.

For the cutoff wall scenario simulation, the MODFLOW horizontal flow barrier (HFB) package was used to reduce conductance terms for adjacent cells where the cutoff wall would be present; The model assumes the cutoff walls extend from land surface to the assumed depth of the Clay/silt. This reduction occurs as a function of a user-specified hydraulic characteristic parameter, which was specified as 1E-6 day-1 based on prior experience with simulations of similar conditions. Furthermore, for the cutoff wall scenario simulation, recharge was eliminated for the enclosed area of the Site under the assumption that a water ingress management scheme would be in place.

Particle tracking was performed for the two modeled scenarios using the MODPATH particle tracking utility. MODPATH simulates advective groundwater flow (i.e., ignoring dispersive and diffusive effects) based on MODFLOW-predicted cell-to-cell groundwater fluxes. In addition to MODFLOW results, MODPATH requires porosity specifications to determine linear groundwater velocities. For these simulations, a generic/default porosity value of 0.3 was specified. Particle starting points were arbitrarily selected at locations up-gradient from the Site. Particles were then simulated forward with MODFLOW to their ultimate discharge point (i.e., no time limit was assigned).

The hypothetical modeling results suggest the hydraulic conditions will be altered once the cutoff wall is installed on-site as groundwater flow will likely go around the cutoff wall to the north and south. However, particle tracking shows that the deflection is minimal and as groundwater flows around the cutoff wall it will tend to track back to the northwest and southwest corners of the cutoff wall ultimately following a similar flow path as before the installation of the cutoff wall. In addition, the particle tracking shows that the deflected groundwater flow path tends to hug the outside walls of the cutoff wall. The overall groundwater gradient stays consistent with some steepening on the eastern and western walls of the cutoff wall. Figure B above indicates that impact on the off-site LNAPL plume will be minimal and the plume will follow a similar path and not be mobilized in different directions. On the northern side of the Site near the CVOC plume the groundwater gradients stay consistent and the flow direction is relatively the same as without the cutoff wall. The impact of

Page 4-114

installation of the cutoff wall on plume (LNAPL and TCE plumes) geometry will be further evaluated during the project design phase.

This alternative does provide for mitigation of SVI concerns via implementation of SSDSs outside of the treatment area and vapor barriers for new construction in areas where vapors may remain present. This alternative also provides a means for assessing achievement of SCGs in soil vapor that may result from VOC remediation, and for evaluating compliance with the SCGs for indoor air in occupied buildings. This alternative includes ECs and ICs to monitor and control potential exposures for those media where SCGs are not obtained, thereby assuring that the SCGs are not exceeded at potential exposure points;

Balancing Criteria:

Long-term effectiveness and permanence: The VOC contaminants in the groundwater, soil, and soil vapor within the AS/SVE ROls would be actively and permanently reduced by this alternative, resulting in an effective and permanent long-term remedy for VOCs in this area. This alternative includes removal and off-site disposal of LNAPL over time, thus permanently reducing the amount of LNAPL in the subsurface. This alternative will result in significant removal of LNAPL via TCH enhanced recovery followed by chemical oxidation of remaining LNAPL and dissolved phthalates beneath the Site. This alternative also provides for long-term control of potential migration of any LNAPL remaining in the on-site source area. Groundwater and LNAPL monitoring does not provide a long-term effective or permanent remedy for groundwater impacts or LNAPL, but it provides a means to document changes in groundwater quality and LNAPL extent and apparent thickness due to other remedial measures and attenuation processes. The SSDS does not significantly remedy soil vapor impacts; however, SSDS operation will gradually reduce soil vapor impacts within its ROI over time and provide long-term effective protection from SVI. Soil vapor and SVI monitoring do not actively remedy soil vapor impacts. However, soil vapor and SVI monitoring do provide a means for documenting changes in soil vapor conditions and the potential for SVI due to other remedial measures and are a long-term effective means for assessing soil vapor conditions and the potential for SVI. Implementation of ECs and ICs will result in an effective long-term remedy from the standpoint of public health as the residual materials remaining after remediation is complete would be isolated from public contact by a cover, prohibition of groundwater usage, controls on Site usage, controls on off-site subsurface access, and an SMP to govern management of residual materials. Periodic inspection and certification would be required, resulting in an effective and permanent long-term remedy;

Reduction of toxicity, mobility, or volume: This alternative provides for a reduction of toxicity, mobility and volume of VOC contaminants in the groundwater, soil, and soil vapor within the AS/SVE ROls. This alternative also provides for a reduction of toxicity, mobility and volume of LNAPL in the on-site area as these materials will be removed. This alternative also provides for a reduction of toxicity, mobility and volume of off-site LNAPL. Through source removal and isolation, it will reduce mobility and volume of groundwater contamination and will provide a means for evaluating reductions in other groundwater contaminants due to other remedial measures or attenuation processes. This alternative reduces the toxicity, mobility, or volume of soil vapor contaminants within the SVE ROI, and provides a means to evaluate reductions in soil vapor contaminants due to other remedial measures. The mobility of soil vapor contaminants would be

Page 4-115

reduced via operation of the SSDS, implementation of a vapor barrier for new construction, and maintaining the cover EC using ICs;

Short-term impacts and effectiveness: The short-term adverse environmental impacts or human exposures would be variable during the activities associated with implementing the Alternative 5 remedial measures. Short-term adverse environmental impacts or human exposures are anticipated to be minimal to moderate for the on-site LNAPL removals and LNAPL recovery aspects of Alternative 5. Although the LNAPL removals are anticipated to be conducted after the existing Site building is removed, measures will be taken to control potential odors, construction-related noise, and impacts from vehicle activity. As additional intrusive activities will occur, there is the potential for short-term impacts. The short-term adverse environmental impacts or human exposures are anticipated to be minimal for the AS/SVE remedial system, groundwater/LNAPL monitoring, soil vapor and SVI monitoring, and SSDS. The intrusive activities for SSDS construction and off-site vapor monitoring point construction would, if necessary, take place inside the off-site buildings. For all remedial activities, an approved HASP and CAMP would be required for the remedial construction and monitoring work and PPE would be utilized by remedial workers to control exposures. CAMP monitoring results would be used to verify that short-term impacts are minimized and to trigger implementation of additional controls if needed. Potential exposures to VOC emissions will be monitored via SVE and SSDS effluent sampling and emissions controls will be used if necessary to ensure that emissions meet Air Guide 1 requirements. Short-term adverse environmental impacts or human exposures are not anticipated in association with implementing ECs and ICs. Following completion of remedial construction and associated cover repairs, there are not anticipated to be any human exposures as the remaining affected media will be covered and the cover would be monitored;

Fugitive emissions will be controlled using multi-phase extraction and the proposed engineering controls. During the remedy, vapor extraction will be performed within the networked extraction wells to remove, separate and treat any generated vapors. In addition, the thermal blanket will be monitoring daily and any necessary repairs will be made as needed. Air monitoring will be performed during the remedy to monitor the engineering controls. Overall, the techniques have a relatively high demand for engineering in the planning phase (4-6 months) and a high need for monitoring and supervision in a short implementation phase.

We further evaluated alternative 5 for short term impacts related to the generation of Dixons due to heating of media containing plasticizers.

There is no evidence that dioxins and furans are formed during a TCH remedy. Dioxins or dioxins-like compounds are formed when organic or inorganic chloride exist and the temperature are between 450 to 800 °C (Aurell and Marklund; 2009; Jansson, 2008); the reaction occurring in an incinerator is extremely complex and there are many factors in addition to combustion temperature influencing dioxin formation. Factors involved in dioxin formation are chorine content; number of benzene rings; the concentrations of metals in samples; O2, CO, and HCl concentration in the combustion chamber (Shibamoto et al., 2007); and residency time in the combustion chamber at elevated temperature. The targeted treatment temperature for the remedy (100 °C) is well below the dioxin formation temperature (450 °C to 800 °C). In addition, even though temperatures at the electrodes will be above 100 °C, less than 2% of the treatment

Page 4-116

areas will experience temperatures above the target temperature of 100 °C (USEPA Engineering Paper – In Situ Thermal Treatment Technologies: Lesson Learned). Therefore, no significant dioxin formation is expected. The TCH system will be designed based on the same design principles employed on past projects in which dioxin emissions, as summarized herein, were extremely low, and in which there was no evidence that dioxin precursor compounds were formed at the fringes of the treatment zone. These protective design elements include: (a) a system of vacuum extraction wells that impose a vacuum on the horizontal and vertical boundaries of the thermal treatment zone; (b) closely-spaced heater-only wells throughout the thermal treatment zone, to ensure uniform heating to target treatment temperatures and a high degree of in situ destruction; (c) an insulated vapor barrier at the ground surface, which sheds rainfall, to ensure capture of vapors within the thermal treatment zone, and to ensure that the top of the thermal treatment zone reaches treatment temperatures; (d) in the case of higher temperature treatment, injection heaters to preheat the vapor collection manifolds, thereby preventing condensation of off-gases, and a thermal oxidizer operated at temperatures ensuring a high destruction and removal efficiency for organic contaminants including dioxins and dioxin precursors; (e) as needed, an air-to-air heat exchanger to reduce the temperature of the off-gases at the oxidizer outlet within a fraction of a second to 200°F, well below the dioxin formation range; and, (f) polishing of off-gas with granular activated carbon prior to the stack.

In addition, during prior operations of the ISTD or TCH technology in conjunction with a flameless thermal oxidizer (FTO) and GAC adsorbers, stack emission will be tested for monitoring dioxin emissions. Stack emissions were measured for 2,3,7,8-TCDD TEQ isokinetically using an XAD-2 sorbent trap in accordance with EPA Method 23. This stack testing protocol was followed at Glens Falls, NY in conjunction with an ISTD thermal blanket pilot study (Goldman Environmental 1996) at MEW during both the thermal blanket and thermal well ISTD demonstrations (Haley & Aldrich, Inc. October 1997; November 1997), and during the full scale ISTD thermal well projects at NFCB (TerraTherm Environmental Services Inc., 1999) and at Alhambra, CA (Baker, et al. 2007). In accordance with EPA Method 23, prior to the sorbent trap, a series of impingers were used to cool the sample stream. The sorbent trap and impingers were submitted for analysis by High Resolution combined with Gas Chromatograph/Mass Spectrometer (HR GC/MS). Source testing results indicate that the discharge rate of Total 2,3,7,8-TCDD TEQ was less than 0.006 ng/dscm during these projects. Additional references can be provided upon request. In summary, there is no evidence to support the contention that ISTD or TCH results in the formation of dioxins or furans, either in the treated soils or in the off-gas.

Implementability: There are anticipated to be some technical limitations to implementing certain aspects of this alternative Thermal enhanced LNAPL recovery using steam or TCH is a proven technology with a track record of success and we do not envision implementation difficulties other than installation of the electrode and recovery well system inside the existing building. Viscosities of the LANPL are anticipated to decrease to the range of No. 1 or 2 oils or less at 212 degrees C based on literature and site specific testing. Thermal conductive heating is a very predictable way of injecting energy into the subsurface, since the thermal conductivity typically

Page 4-117

only varies a factor of 3-5 for most geologies (the thermal conductivity is predominantly a function of the soil saturation and density/porosity). Impacts to local utilities are evaluated and handled routinely during TCH. A safety distance of approximately 10-12 ft to any heat sensitive utilities from the perimeter heaters is a typical objective. Heaters near utilities use separate circuits and can be adjusted separately from the rest of the wellfield to control temperature. Temperature monitoring points can be installed along the utility corridors and connected to a temperature alarm system to monitor the temperatures adjacent to the lines. Materials of construction and the type of the utility line determine what temperature will be met along the utility lines. Power lines are typically designed for up to 40 degrees C, water lines (depending on material) a little higher, sewer lines are typically around 50 degrees C. In addition, minimal temperature increases are targeted along gas and communication lines. A comprehensive utility survey will be performed prior to implementation. Emergency generators are used to keep the vapor and liquid recovery systems running in the event of power outages to control vapor and liquid migration. The energy demand for the proposed temperatures should be able to be managed by Con Edison. The proposed remedy allows for use of either electrical or natural gas to power the system. During the design stage, a numerical model will be produced that will provide a much more detailed breakdown of the power usage. However, please see the proposed power usage estimate based on our preliminary design model utilized at this stage of the project. The energy demand for the project is related to the treatment system and heater power usage, and varies depending on the phase of the project. The tables below summarize the breakdown for the duration of the project. In reality, the power usage is typically higher at the beginning of the project where the site is heating up, while the power usage decreases after reaching the boiling point at the site. For scenario where target temperature is 100 °C:

Power usage treatment

system Power usage heaters

100 °C scenario Power usage,

average Total

power Power usage,

average Total

power

Days kW kWh kW kWh

Shake-down 5 161 19,000 326 39,000

Heating to boiling point 64 161 248,000 977 1,502,000

Boiling and drying 98 161 379,000 977 2,296,000

Sampling/analysis phase 5 161 19,000 977 117,000

Post treatment vapor extraction 14 161 54,000

Total 186

719,000

3,954,000

Page 4-118

The average energy demand for the thermal treatment project is 161 kw (161 kw/ 110 V=1,463.6 A). The former operations at NuHart required 3-phase electric feeds to the Site. The current site has several active power outlets with 2,000 amps capacity (Appendix E). Based on this the existing infrastructure is in place to perform this work. We have also contacted Con Edison with respect to the former NuHart power demand as well as the above proposed power demand. While unable to confirm what the historic power draw was, Con Edison did summate that with the infrastructure currently in place that the demand was similar or more than the above referenced table. Con Edison advised that the above demand would be able to be met but suggested that advanced planning be made prior to the scheduled usage.

In-situ thermal conductive heating has been successfully used next to sensitive infrastructure in urban areas or below the buildings in the United States and European countries. For example, in a residential area in Reerslev, Denmark a vast mass of contamination of PCE was found. The treatment period was 169 days and the target temperature was 100 °C. By the end of the heating period, 28 soil samples were taken to document the effect of the remediation. 23 soil samples were below the detection limit; average post-treatment concentration was 0.012 mg/kg and maximum post-treatment concentration was 0.057 mg/kg. GZA has also performed thermal heating in dense urban areas. Two projects that GZA has performed the work were in Los Angeles and Santa Monica California. Thermal heating was successfully performed in both areas with sensitive receptors like the NuHart Site (Appendix D). In addition, the NYSDEC has recently approved a thermal project in Region 2 for the Former Acco Brands Site which is located at 320 Skillman Avenue in Long Island City, NY.

Based on our research and experience with chemical oxidation at sites across the country, the opportunity to capitalize on the residual heat from a TCH remedy to heat activate sodium persulfate (Na2S2O8) will provide the most cost effective as well as aggressive oxidation strategy for polishing residual phthalates remaining after TCH (Wang et al., 2014). Combined and aggressive thermal/chemical oxidation remedy will optimize overall project costs (USEPA, 2014) by taking advantage of the “sweet spots” where these technologies provide the most cost effective reduction of phthalate mass, both in the soil and dissolved phases. Former Building 1211 Underground Storage Tank Site (FTC-088/SWMU 169, Fort Carson, Colorado) is a good example supporting activated sodium persulfate chemical oxidation of BEHP) (Appendix F). Additional laboratory scale studies show that phthalates respond to oxidation via hydrogen peroxide and ozone injection (Huang, 2010). During the design phase, GZA will perform a b bench scale study to optimize the BEHP oxidation results.

Since readily-available AS/SVE and SSDS remedial and monitoring technologies would be utilized, much of the proposed monitoring network is already present, there is no groundwater usage, and groundwater, LNAPL, and soil vapor/SVI monitoring procedures have already been conducted under the NYSDEC-approved work plans, there do not appear to be significant technical limitations to these aspects of Alternative 5. Design of the AS and SVE systems will need to take

Page 4-119

stratigraphic variations into account. Access issues may limit off-site SVI monitoring. An SMP and an environmental easement would be required, both of which may be readily implemented. The existing street-opening permit process is anticipated to facilitate implementation of the off-site IC, which is anticipated to be posting of an environmental notice for street-opening permits in the Site vicinity. It is anticipated that this alternative would be implemented in stages, each of which may last at least several months; the overall construction period for this alternative is anticipated to be one year and will be affected by the redevelopment schedule. Installation of the on-site groundwater cut-off wall will be challenged but is achievable. Subsurface obstructions may have to be pre-cleared, a comprehensive utility survey will need to be performed, and utilities may have to be relocated and/or temporarily capped and installed through the cutoff wall.

Cost-effectiveness: This alternative provides long-term and short-term effectiveness and results in reductions in toxicity, mobility, and volume for LNAPL, VOCs in groundwater, soil and soil vapor. This system is also likely to indirectly reduce groundwater and soil vapor impacts outside of the ROI. The SSDS will also provide long-term and short-term effectiveness, but will not result in significant reductions in toxicity or volume of soil vapor VOCs (although mobility will be significantly reduced). This alternative also provides long-term and short-term effectiveness for control of potential LNAPL migration off-site via the cutoff wall, in-situ TCH enhanced LNAPL recovery followed by ISCO, and off-site recovery systems and results in reductions in toxicity, mobility, and volume for LNAPL. Design, construction, and operating costs for the in-situ thermal treatment will be high. Off-site LNAPL removal system will be moderate to high. AS/SVE remedial system and SSDS design, installation, operation, and monitoring costs are anticipated to be moderate, and the groundwater, LNAPL, soil vapor, and SVI monitoring design and implementation costs are relatively low. Overall, the costs for this comprehensive alternative are moderate, relative to its overall effectiveness. The cost-effectiveness for the remedial and monitoring components are increased somewhat when used in conjunction with the ECs/ICs that control potential exposures.

Land use: This alternative is protective of the current and reasonably-anticipated land use of the Site, which is presently vacant and anticipated to be redeveloped with a restricted residential and/or commercial use, as the soil, groundwater and soil vapor impacted by VOCs within the AS/SVE system ROI would be remediated, mitigation of potential on-site SVI concerns would occur, LNAPL will be removed from the source area and off-site areas, potential off-site migration of LNAPL would be controlled, groundwater use is not occurring or contemplated, a cover will remain present over impacted materials, and monitoring data would be available to assess LNAPL changes, groundwater quality, and potential SVI concerns on-site. This alternative is also protective of the current and reasonably-anticipated land use in the Site vicinity, as the AS/SVE system is anticipated to reduce or eliminate off-site soil, groundwater and soil vapor impacts thereby mitigating potential SVI concerns, additional SVI mitigation would be provided by the SSDS, LNAPL will be removed, groundwater use is not occurring, a cover will remain present or be re-installed over impacted materials, and monitoring data would be available to assess changes in the condition of subsurface media over time. Under Alternative 5 materials exceeding applicable SCGs would be isolated from the public via cover, controls on land use, and controls on groundwater use. These controls would be implemented on-site via an environmental easement and an SMP and off-site via the existing street-opening permit process and posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present.

Page 4-120

Modifying Criteria:

Community Impact: The on-site remedy consists of Installation of a LNAPL cutoff wall, Enhanced LNAPL Recovery via TCH, ISCO, AS/SVE and Target Site removals. This remedy will not require the demolition of the existing building covering the Registry Site for remedial construction.

Traffic: This alternative is not anticipated to significantly impact traffic during this timeframe. Traffic increases will stem from material deliveries and employees travelling to and from the Site. During installation of the LNAPL cutoff wall a temporary Sidewalk closure may be necessary to facilitate the installation of the Wall along Dupont, Clay and Franklin Street. Sidewalk closures would be temporary and be reopened upon completion. The TCH System would be installed inside the building footprint and would not cause any significant disruption to traffic in the area. During operation of the TCH System, sidewalk closures may be considered on Franklin and Dupont Street where pedestrians would be re-routed to the opposing sidewalk. At this time, closure of street parking along any of the adjoining streets is not anticipated during operation of the TCH System. During the Target, on-site removals there will be an increase in truck traffic as waste truckers will be utilized to remove soil from the Site. The anticipated waste stream for this material would be a combination of urban fill and hazardous waste which will be transported by a comb ination of triaxles and long haul trailers, respectively. The trucking during this portion is set for localized excavation areas and is not anticipated to have a long-term impact on traffic patterns.

Noise: This alternative will utilize heavy equipment to install LNAPL Cutoff Wall, TCH system, Extraction wells, AS/SVE wells, ISCO system and Target on-site removals. Remedial construction elements will provide a short-term impact on noise levels during installation and operation. The elements of this remedy can be installed, operated and/or performed within the existing building footprint which would greatly reduce noise impacts.

Air Quality: This alternative is not anticipated to significantly impact air quality. It is noted that during the remedy, community air monitoring will be performed during all remedial activities. All extracted vapors from the TCH treatment and AS/SVE system will be treated adhere to NYSDEC standards prior to discharge. Due to the short time frame of the installation of the remedial components, exhaust from the heavy machinery is not anticipated to be significant.


The total estimated costs for Remedial Alternative 5 is shown on Table 4.1.5.9.

Page 4-121



Description Cost


Initial Capital Costs LNAPL Physical Barrier and Extraction/Disposal $3,055,700 $3,055,700 Thermal Conductive Heating with In Situ Chemical

Oxidation $3,977,300 $3,977,300

Targeted Soil Excavation/Disposal $550,000 $550,000 AS/SVE (TCE-impacted area) $183,600 $183,600 Groundwater/LNAPL Monitoring Network $36,600 $36,600 SSDS and Vapor Barrier $364,200 $364,200 Soil Vapor/SVI Monitoring Network $39,600 $39,600 Implement ECs and ICs (environmental easement, SMP) $46,000 $46,000 Initial Capital Cost Subtotal: $8,253,000 $8,253,000 O&M Net Present Worth over Anticipated O&M Periods LNAPL Extraction (off-site, 10 years) $2,964,700 $1,290,000 AS/SVE (4 years) $1,179,400 $223,700 Groundwater/LNAPL Monitoring (6 and 10 years) $3,187,300 $1,126,500 SSDS (6 years) $1,578,700 $436,300 Soil Vapor/SVI monitoring (6 years) $972,800 $268,900 Certification and Reporting (30 years) $255,400 $255,400 O&M, Certification and Reporting Net Present Worth

Subtotal: $10,138,300 $3,600,800

Post-Remedial Capital Costs LNAPL Extraction System Removal (10 years) $148,400 $267,800 AS/SVE System Removal $6,900 $14,800 Groundwater and LNAPL Monitoring Network

Replacement (10 years) $19,500 $35,200

SSDS Removal (6 years) $13,000 $26,400 Soil Vapor/SVI Monitoring Network Abandonment (6

years) $16,000 $32,600


O&M/Certification/Reporting) $18,595,100 $12,230,600 Note: Assumed interest rate is 5% and assumed inflation rate is 2%. All subtotal and total costs are rounded to the nearest $100.

Page 4-122

4.2 RECOMMENDED REMEDIAL ALTERNATIVE

4.2.1 Alternative Evaluation

These comprehensive remedial alternatives have been evaluated and a recommendation is developed; a summary of this evaluation is presented in Table 4.2.1. Specifically, each alternative provides various degrees of remedial success and are limited by factors in each of the nine evaluation criteria. The below evaluation is based on elements of each alternative as they pertain to the Phthalate Plume and the TCE plume. Each Alternative would include Limited Site Removals which would assist in the removal of potential source material, even though the tanks have been closed in place. In addition, each alternative includes AS/SVE in the TCE plume; The current timeline is approximately four years of operation but actual timelines may extend beyond based on site conditions. Each Alternative will implement engineering and institutional controls that will be placed on the Site in order to mitigate exposure and identify restrictions to future activities/uses on the Site.

Alternative 1 (No Action remedial alternative) was screened against the threshold criteria and was rejected as it would not be protective of public health and the environment or result in conformance with SCGs. This alternative was not further evaluated against the balancing criteria and is not considered further herein.

Alternative 2 will reduce source LNAPL on the Site and can be implemented with the building still in place. While the remedy will have minimal disruption to the community, the operation of the product recovery systems would take a significant amount of time, in turn limiting the use of the Site during the remedy phase. For Alternative 2 to be viable, development would need to occur during implementation of the remedy which would result in a minimal amount of LNAPL recovery prior to development of the Site. While this remedy provides a permanent solution, there are limitations to the effectiveness of the remedy as recovery wells will operate in limited areas where recovery wells can be installed (subsurface anomalies and future Site uses) and rely on LNAPL migration to the recovery point. Based on previous experience with LNAPL recovery systems with the highly viscous nature of the LNAPL at this Site, LNAPL recovery rates will decline over time and it is anticipated that the system designed for current conditions may reach the limits of its effectiveness within 10 years of operation. Thereafter, LNAPL recovery methods may require modification for continued effectiveness and/or further LNAPL recovery may become impractical. The AS/SVE under this remedy would be implemented in conjunction with the LNAPL recovery. There would be no LNAPL cutoff wall on-site as part of this remedy and there will be no hydraulic control of the on-site LNAPL plume. If a significant event were to occur in the area (storm, underground water/septic/storm main bursting), this remedy would not allow for control of the plume.

Alternative 3 without the ISS option contains the same remedial elements as Alternative 2 with respect to the approach but also contains the ISCO remedy in the target excavation area. To effectively apply ISCO, a substantial reduction of LNAPL would be required. As the proposed LNAPL recovery system will operate for many years prior to substantial LNAPL reduction, ISCO would not be effective in the near future.

Remedial Alternatives

Evaluation CriteriaAS/SVE(onsite)

Offsite Physical Barrier

LNAPLExtraction &

Disposal

Groundwater& LNAPL

Monitoring

Soli Vapor &SVI Monitoring

Limited Onsite Removals

ECs & ICs

LNAPL Barrier, Extraction & Disposal

Target Soil Excavation & Disposal w/In-situ

Treatment

In Situ Soil Stabilization/Solidificatio

n

AS/SVE(Onsite)

Groundwater& LNAPL

Monitoring

SSDS &Vapor Barrier

Soil Vapor &SVI Monitoring

ECs & ICsSoil & LNAPLExcavation &

Disposal

LNAPL Barrier & Extraction

AS/SVE (onsite & offsite)

Groundwater & LNAPL

Monitoring

SSDSs &Vapor Barrier


ECs & ICs

LNAPL Barrier, Extraction &

Disposal

Thermal Conductive Heating

with In Situ Chemical Oxidation

Target Soil Excavation &

Disposal

AS/SVE (onsite & offsite)

Groundwater& LNAPL

Monitoring

SSDS &Vapor Barrier


ECs &ICS

Threshold Criteria

Overall Protection of Public Health and the Environment

Protective of publichealth and

environment


environment


environment

Indirectly protectiveof public health and

environment


environment

Somewhat protectiveof public health and

environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment


environment

Compliance with SCGsProvides for

compliance withSCGs

Provides for partialcompliance with

SCGs

Provides for limitedcompliance with

SCGs

Provides data toassess compliance

wain SCGs


with SCGs


SCGs

Does not provide forcompliance with

SCGs

Provides for limitedcompliance with

SCGs


SCGs


SCGs

Provides forcompliance with

SCGs


with SCGs

Provides for compliancewith SCGs in indoor air


with SCGs


SCGs


SCGs onsite


SCGs


SCGs


with SCGs

Provides for compliancewith SCGs in indoor air


with SCGs


SCGs


SCGs


SCGs onsite


SCGs


SCGs onsite


with SCGs

Provides for compliance

with SCGs in indoor air


with SCGs


SCGs

Long-Term Effectiveness and Permanence

Provides effective permanent remedy

Provides permanentremedy for limited

area, noeffectiveness forLNAPL reduction

Provides permanent remedy, limited effectiveness for LNAPL reduction

Provides data toevaluate

effectiveness ofother measures



Provides partial permanent remedy,

limited effectiveness for LNAPL reduction


to controlexposures

Provides permanent remedy, limited

effectiveness for LNAPL reduction

Providers partial permanent remedy,

moderate effectiveness for LNAPL reduction

Provides permanent remedy, limited





Provides effective SVI protection




to controlexposures

Providespermanent remedy

and LNAPLreduction

Provides permanent remedy, partial









to controlexposures

Provides permanent remedy, limited effectiveness for LNAPL reduction


Providers partialpermanent remedy,

moderate effectiveness for LNAPL reduction








to controlexposures

Reduction of Toxicity, Mobility, or Volume

Provides for reductionscontaminant toxicity, mobility and volume

Reduces potentialmobility of offsite

LNAPL, noreductions in toxicity

or volume

Reduces volume of LNAPL somewhat

Provides data toevaluate reductionsin toxicity, mobility

and volume


and volume

provides some reduction in toxicity, mobility and volume

of LNAPL andimpacted soil

Cover system ECreduces

contaminantmobility

Reduces volume of LNAPL somewhat.

provides protection for potential LNAPL mobility

offsite

Provides forreductions in

contaminant toxicity, mobility and volume

Reduces potentialmobility of onsite

LNAPL, noreductions in toxicity

or volume

Provides for reductions in contaminant toxicity,

mobility and volume


and volume

Does not significantly reduce contaminant toxicity or volume, reduces mobility.


and volume


contaminantmobility

Significantlyreduces volumeand mobility of

LNAPL

Reduces volume of LNAPL. provides

protection for LNAPL mobility

Provides for reductions in contaminant toxicity,

mobility and volume


and volume

Does not significantlyreduce contaminantWidely or volume,reduces mobility


and volume


contaminantmobility

Reduces volume of LNAPL somewhat. provides protection for potential LNAPL

mobility offsite

Significantlyreduces volumeand mobility of

LNAPL

Provides forreductions in


Provides for reductions in



and volume

Does not significantlyreduce contaminantWidely or volume,reduces mobility


and volume


contaminantmobility

Short-Term Impacts and Effectiveness

Minimal short-termimpacts, mitigationmeasures (HASP.

CAMP) are effective

Moderate short-termmeasures (HASP,

CAMP) are effective

Moderate short-termmeasures (HASP,

CAMP) are effective

Minimal short- and long-term impacts, mitigation

measures (HASP.CAMP) are effective



Low to moderateshort-term impacts.odor control may be

needed

No short termimpacts

Moderate short-and long-term impacts mitigation

measures (HASP, CAMP) are effective

Moderate short-termimpacts odor control

may be needed

Significant short-and long-term impacts, significant

mitigation measures required

Minimal short-term impacts, mitigationmeasures (HASP.

CAMP) are effective




CAMP) are effective

Minimal short- and long-term impacts,

mitigationmeasures (HASP.

CAMP) are effective


Significant short-and long-term impacts,

significant mitigation measures required

Moderate short- and long-term impacts,


CAMP) are effective


CAMP) are effective



Minimal short-term Impacts. mitigation measures (HASP,

CAMP) are effective



CAMP) are effective


Moderate short- and long-term impacts,


CAMP) are effective

Significant short-and long-term impacts,

significant mitigation measures required

Moderate short-termimpacts odor control

may be needed


CAMP) are effective



CAMP) are effective

Minimal short-term Impacts. mitigation measures (HASP,

CAMP) are effective



CAMP) are effective


ImplementabilityNo significanttechnological

limitations

No significanttechnical limitations

other thansubsurface

infrastructure

Technical limitationsdue to subsurface

infrastructure

No significanttechnicallimitations

Ne significant technical limitations. private

property access may limit implementation

Potential technicallimitations due to

odors


No significant technical limitations, subsurface

infrastructure maypresent limitations


odors




No significanttechnical limitations.

No significant technical limitations, private



Technical limitations due to subsurface

infrastructure, odor, noise and materials

management concerns.


infrastructure




No significant technical limitations, private




infrastructure, private property access may limit implementation.



odors

No Munificenttechnicallimitations



No significant technical limitations,

private property access may lime implementation


Cost-EffectivenessCosta are low

relative toeffectiveness

Costs are moderaterelative to overall

effectiveness,


effectiveness.

Costs are lowrelative to overall

effectiveness for data gathering




effectiveness.


effectiveness


effectiveness.

Costs are low tomoderate relative tooverall effectiveness.

Costs are highrelative to overall

effectiveness.

Costa are lowrelative to

effectiveness



Costs are low relative to effectiveness




effectiveness


effectiveness.


effectiveness.

Costs are moderaterelative to

effectiveness.



Costs are lowrelative to

effectiveness




effectiveness


effectiveness.


effectiveness.


effectiveness.

Costs are moderaterelative to

effectiveness.



Costs are low relative to effectiveness




effectiveness

Land Use Protective of landuse

Protective of landuse





























Modifying Criteria

On-Site Remedial Activities Community Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact Moderate Impact

Significant Community Impact

No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant ImpactSignificant Community

ImpactsNo Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact Moderate Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact No Significant Impact

Total Cost (30 years) $1.373,100 $436,500 $4,145,100 $3,273,400 $949,800 $964,100 $301,400 $5,739,700 $1,437,000Not Selected as Part of

Remedy $1,369,900 $3,243,400 $1,477,700 $994,600 $301,400

$15,768,400(incl. barrier)

(plus $1,826,590for tent)

$4,780,300 $1,939,100 $3,275,200 $1,955,900 $1,165,000 $301,400 $5,739,700 $1,939,100 $1,437,003 $1,369,900 $3.243,400 $1,477,700 $995 $301,400

Total Cost (Estimated duration 1 or remedies with completion)

$429,100(4 years)

$436,500$2,679,500(10 years)

$1,292,300(6 & 12 years)

$322,500(8 years)

$964,100 $301,400$3,753,660(10 years) $1,437,000 N/A

$422,100(4 years)

$1,198,300(6 & 10 years)

$626,000(6 years)

$330,500(6 years)

$301,400

$15,768,400(incl. barrier)

(plus $1,826,590for tent)

$4,061,200(10 years)

$878,400(4 years)

$1,265,300(6 & 15 years)

$760,300(6 years)

$378,300(6 years)

$301,400

$3.753.660{8 years)

515368,409$878,400(4 years)

$1,437,000S422,100(4 years)

$1,188.300(6 & 10 years)

$626.000(6 years)

$330.500(6 years)

$301,400

Total Alternative Cost (30 years)

Total Alternative Cost (Variable durations)

This table was developed using information from previous submissions performed by FPM Group

$18,595,100

$12,230,600$6,425,400

$8,518,300$22,366,000

(potential $1,826,500 for tent)

$11,407,400 $15,066,700$28,851,600

(potential $1,826,500 for tent)

TABLE 4.2.1EVALUATION OF REMEDIAL ALTERNATIVES

FORMER NUHART PLASTIC MANUFACTURING SITE #224136280 FRANKLIN STREET, BROOKLYN, NEW YORK

Alternative #5Alternative #2 Alternative #3 Alternative #4

Page 4-124

Under Alternative 3, ISS was evaluated as a potential remedial approach for the LNAPL plume in lieu of the on-site extraction. Solidification/stabilization of the source material will reduce its potential for source contamination migration and further groundwater impacts, but not to remove the on-site source material. This remedy will make a relatively immobile plume to slightly less immobile; and would render the phthalates unrecoverable in the future making them a permanent fixture below any proposed development. In addition, the alternative would significantly hinder the elements necessary for a foundation and would require that the developer have a final development drawing set that cannot be altered without a significant effort once the remedy is commenced. ISS would require demolition of the existing building and evaluation of environmental enclosure during the implementation of the remedy. If an environmental enclosure was required, traffic in the area would be significantly impacted during the mobilization and erection of the environmental enclosure. Street and sidewalk closures and parking restrictions would be required during the entire remedy application which is anticipated to be greater than one year. Without an enclosure, fugitive dust and odors from the mixing application would be a challenge to control. ISS would require bench and pilot testing to determine if it could be implemented for the phthalate LNAPL, and subsurface obstructions (foundations, utilities, and pile supports) present significant concerns. There would be no LNAPL cutoff wall on-site as part of this remedy which will provide no hydraulic control of the on-site plume during the ISS operation.

Alternative 4 would reduce source LNAPL significantly on-site but there are significant technical limitations to implementing certain aspects of this remedy. This alternative would require the demolition of the building in order to execute the remedy. While excavation may be considered as part of the future development (development plans have not been started for the Registry Site), this remedy would require soil above the LNAPL zone to be removed, requiring additional costs for transportation and disposal as well as the import of certified clean backfill. For the on-site soil excavation and LNAPL removal, the excavation would need to extend to at least 16 feet below grade with associated shoring, dewatering, LNAPL removal, and backfill placement. This remedy is anticipated to present considerable obstacles for implementation of the remedy, including soil and fluids management on-site, noise and odor suppression, and transportation issues. This alternative would very likely require that an environmental enclosure be erected for the duration of excavation operations. Traffic in the area would be significantly impacted during the mobilization and erection of the environmental enclosure and during implementation of the remedy. Street and sidewalk closures and parking restrictions are expected during the entire remedy which is anticipated to be greater than one year. Because of the high viscosity of LNAPL observed under the current condition, dewatering operations for fluids management during excavation will pose a significant obstacle. Thermally enhancing the water/LNAPL mobility will be considered in order to avoid a potential seizing of the dewatering system. The implementability of chemical treatment of LNAPL (such as with surfactants) to increase its mobility and recovery would have to be demonstrated through bench and pilot testing in lieu of thermally enhancing the LNAPL. Dewatering will be necessary as a consideration for the transportation of LNAPL impacted soil from the Site. Since the material is considered hazardous and will likely go for disposal to a long-haul facility, shipment of saturated soils increases the weight of the load which

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would result in underfilled trucks (by volume) as most of the weight would be water/LNAPL based. This would result in increased trucking and stress to the local traffic patterns as well as increased costs to the Owner. There would be a physical barrier as an element of the support of excavation but this element may or may not be watertight while physical barrier would provide some hydraulic control if a significant event were to occur in the area (storm, underground water/septic/storm main bursting), this remedy would not allow for control of the plume.

Alternative 5 will reduce source LNAPL significantly on-site and can implemented with the building still in place. This remedy is an enhancement of the Alternative 3 where reducing the viscosity of the LNAPL will enhance the recovery, removal, treatment and disposal of the LNAPL plume. The remedy will have a similar impact on the local traffic in the area as Alternative 2 and 3 (without ISS) and can be performed with or without the building in place. This alternative will significantly expedite the timeline of recovery via thermal enhancement as compared to Alternative 2 and Alternative 3’s conventional extraction methods to asymptotic recovery. The remedy duration is similar to the Alternative 4 for the LNAPL remedy but also allows the flexibility to extend the treatment zone to the AS/SVE area where TCH is also a proven technology to treat TCE related contamination. This remedy also contains a permanent LNAPL cutoff wall providing hydraulic control of the on-site plume during and after the remedy. If a significant event were to occur in the area (storm, underground water/septic/storm main bursting), having a permanent LNAPL cutoff wall will alleviate the potential for migration of the on-site plume off-Site and the potential from the off-Site plume re-entering the Site. This alternative also will provide flexibility for future development on the Site to have the ability to remove any of the remaining source of LNAPL since it will be contained within the LNAPL cutoff wall (within the Site boundaries) and also would not be solidified as a solid mass through ISS. This remedy will have minimal disruption to the local community as also in Alternatives 2 and 3, will remove more source than Alternative 2 and 3, by (1) this remedy does not require evaluation and/or installation of an environmental enclosure; (2) resulting in less vehicle (truck) traffic at the site; The TCH System would be installed inside the building footprint and would not require significant closure of lanes, sidewalks or parking restrictions.; (3) resulting in less noise impacts; Remedial construction elements will provide a short-term impact on noise levels during installation and operation. The elements of this remedy can be installed, operated and/or performed within the existing building footprint which would greatly reduce noise impacts. (4) Reducing the potential of air quality impact.

4.2.2. Recommended Remedial Alternative

As evaluated in the previous section, the recommended remedial alternative is:

Alternative 5: Groundwater Cutoff Walls with LNAPL Extraction/Disposal, Targeted Excavation, In-Situ Thermal Treatment Followed with In-Situ Chemical Oxidation, Off-Site Physical Barrier, Air Sparging/Soil Vapor Extraction, Groundwater/LNAPL Monitoring, Sub-Slab Depressurization and Vapor Barrier, Soil Vapor/SVI Monitoring, and ECs/ICs.

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This recommendation is based on the evaluation of each alternative relative to the nine criteria, the anticipated near-term redevelopment of the Site, the continued absence of groundwater use, the future presence of protective cover materials on-site and off-site and the limited exposure scenarios for the identified impacts. Alternatives 5 is recommended because this alternative will provide the highest level of protection

to human health and the environment and will comply with New York State SCGs. Further, it will

provide the best balance of the primary balancing criteria, as described in Section 4.1, by: 1) greatly

reducing the source of contamination, both on-site and off-site, 2) addressing off-site contamination

with a combination of remedial methods, creating conditions to minimize groundwater

contamination to the extent practicable, and 3) greatly minimizing impact to the community including

traffic, noise, and air quality that are anticipated to be significant with Alternative 3 (ISS) and

Alternative 4 (soil excavation). When considering all the evaluation criteria, Alternative 5 is the

preferred alternative to address the on-site source material, and will enable an off-site remedy to be

effectively implemented. It will provide a high degree of long-term effectiveness in preventing further

off-site migration by removing the source material. Specifically, Alternative 5 will provide

significantly more source removal than Alternative 2 and Alternative 3 while having a similar impact

in the local community during the remedy installation but a significantly shorter duration of

operation. The ISS (Alternative 3) will take a relatively immobile plume and render more immobile

without removing any of the source while significantly limiting the potential use of the property after.

ISS will also potentially require the installation of an environmental enclosure and associated impacts.

Alternative 4 will significantly remove source material on-site but will have a more significant impact

on the local community. In addition, to restrictions on parking, it is anticipated that sidewalks and

lanes will be closed for the duration of the remedy and there would be a significant increase in long

haul trailers in the community congestion the already tight confines of this area. Alternative 5 was

selected based on the flexibility it provides for the building use after the remedy, its minimal impact

to the local community, the long-term engineering control of a LNAPL barrier wall encompassing the

on-site Registry plume during remediation, the potential to remove any remaining source in future

developments and the timeliness of the remedy compared to the other Alternatives.

The recommended remedial alternative (Alternative 5) includes the following elements:

Implementation and control of on-site ECs and ICs under an environmental easement for the Site. Implementation and control of off-site ECs and ICs would be governed by the existing street-opening permit process and an environmental notice.

ICs to include Site and groundwater usage restrictions, and an SMP to control Site use and potential on-site exposures to soil, soil vapor, LNAPL, and/or groundwater. The SMP would include provisions for operation, maintenance, monitoring, annual certification, and other procedures necessary to implement the ECs and ICs. The SMP would also include provisions for additional remedial measures that may be needed for future redevelopment of the Site. Access to the off-site subsurface is presently controlled by an IC consisting of a street-opening permit process that is required for penetration of the existing EC (sidewalks/pavement). An additional IC will be needed to control potential exposures during off-site subsurface activities

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and would include posting of an environmental notice for street-opening permits requested in the area where Site-related subsurface impacts are present.

Targeted soil excavation and disposal is recommended to remove and dispose LNAPL-saturated soils that may be present in proximity to the USTs and piping trench systems formerly used to store and convey phthalates and Hecla oil during the former plastic manufacturing process and the VOC-impacted soils (above the water table) in the northeastern corner of the Site. The previously-closed USTs and piping trench systems would also be removed. Implementing an AS/SVE system to remediate soil and groundwater VOC impacts identified on the northeastern portion of the Site and in the downgradient vicini ty. SVE would also reduce soil vapor VOC concentrations in on-site and off-site areas within its ROI. Effluent monitoring would be performed to evaluate the reduction in VOC concentrations over time and confirm that emissions from the SVE system meet regulatory requirements and determine if effluent treatment is necessary. Soil vapor monitoring would be used in conjunction with the SVE to evaluate the anticipated reduction in soil vapor VOC concentrations over time.

Implementing an SSDS and vapor barrier for the portion of the off-site NuHart property where TCE-impacted soil vapors have been identified and the potential for SVI has been documented. SSDSs would also be implemented for off-site properties on the north side of Clay Street if SVI monitoring indicates that mitigation is necessary. SVI and soil vapor monitoring would be used in conjunction with the SSDS to confirm that SVI is not occurring.

Installing of two groundwater cut-off walls and off-site LNAPL extraction wells to prevent potential LNAPL migration onto an off-site property which is currently under consideration as a potential school and between on-site and off-site areas, and to remove LNAPL from off-site areas. The first groundwater cut-off wall will encompass the majority of the on-site LNAPL plume that abuts Dupont and Franklin Street and will be placed around the footprint of the majority of the LNAPL source area. This remedial strategy will prevent LNAPL that may remain outside of the cut-off walls from re-entering the remediated area, prevent any off-site migration of LNAPL during the implementation of in-situ thermal conductive heating and prevent potential off-site migration of any LNAPL in the unlikely event that LNAPL remains on-site following in-situ remediation. Extraction and disposal of LNAPL from the adjoining off-site areas to the west and south would be conducted to remove LNAPL from the Site, from beneath adjoining sidewalks, and from beneath portions of the adjoining Dupont and Franklin Streets. Extraction and disposal of LNAPL would also be conducted in off-site areas to include the sidewalk area adjoining portions of the east and south sides of the Greenpoint Playground, the sidewalk area at the southwest corner of the Franklin Street/Dupont Street intersection (if monitoring results indicate LNAPL in this area), and the sidewalk area on the southeast corner of the Franklin Street/Dupont Street intersection. These additional off-site extraction areas will also remove some of the LNAPL present beneath the adjoining streets.

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TABLE 4.2.2

ESTIMATED COSTS FOR

RECOMMENDED REMEDIAL ALTERNATIVE 5

Description Cost


Initial Capital Costs

LNAPL Physical Barrier and Extraction/Disposal $3,055,700 $3,055,700

Thermal Conductive Heating with In Situ Chemical Oxidation $3,977,300 $3,977,300

Targeted Soil Excavation/Disposal $550,000 $550,000

AS/SVE (TCE-impacted area) $183,600 $183,600

Groundwater/LNAPL Monitoring Network $36,600 $36,600

SSDS and Vapor Barrier $364,200 $364,200

Soil Vapor/SVI Monitoring Network $39,600 $39,600

Implement ECs and ICs (environmental easement, SMP) $46,000 $46,000

Initial Capital Cost Subtotal: $8,253,000 $8,253,000

O&M Net Present Worth over Anticipated O&M Periods

LNAPL Extraction (off-site, 10 years) $2,964,700 $1,290,000

AS/SVE (4 years) $1,179,400 $223,700

Groundwater/LNAPL Monitoring (6 and 10 years) $3,187,300 $1,126,500

SSDS (6 years) $1,578,700 $436,300

Soil Vapor/SVI monitoring (6 years) $972,800 $268,900

Certification and Reporting (30 years) $255,400 $255,400

O&M, Certification and Reporting Net Present Worth Subtotal: $10,138,300 $3,600,800

Post-Remedial Capital Costs

LNAPL Extraction System Removal (10 years) $148,400 $267,800

AS/SVE System Removal $6,900 $14,800

Groundwater and LNAPL Monitoring Network Abandonment (10 years) $19,500 $35,200

SSDS Removal (6 years) $13,000 $26,400

Soil Vapor/SVI Monitoring Network Abandonment (6 years) $16,000 $32,600

Post-Remedial Capital Cost Subtotal: $203,800 $376,800

TOTAL COST (Initial and Post-Remediation Capital, O&M/Certification/Reporting) $18,595,100 $12,230,600

Note: Assumed interest rate is 5% and assumed inflation rate is 2%. All subtotal and total costs are rounded to the nearest $100.

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An in-situ thermal treatment system is recommended for installation within the cutoff wall to enhance the mobility and recovery of LNAPL. GZA recommends thermal conductive heating to enhance mass removal and shorten the LNAPL recovery timeframe. Following the completion of thermal treatment and LNAPL recovery, the residual contaminants would be treated with ISCO through well injection. In-situ thermal treatment followed by ISCO would directly address the LNAPL in the groundwater and impacted soil on the Site and would also indirectly address the SVOCs and VOCs in the northwest area.

Groundwater and LNAPL monitoring would be implemented to provide the data needed to confirm that groundwater impacts are being reduced by the AS/SVE system, to confirm that LNAPL migration is not occurring, and to document the anticipated reduction in LNAPL extent and apparent thickness in the on-site and off-site areas over time.

As shown in Table 4.2.2, the capital cost for the recommended remedial alternative is $8,253,000and includes preparing an SMP, implementing an environmental easement for the Site and an off-site IC, implementing groundwater cutoff walls to prevent potential LNAPL migration onto the property that may be developed with a school, targeted soil excavation and disposal to remove and dispose LNAPL-saturated soils that may be present in proximity to the on-site USTs and piping trench systems and the VOC-impacted soils above the water table in the northeastern corner of the Site, TCH or SER to enhance the recovery of LNAPL, on-site and off-site LNAPL removal, implementing an AS/SVE system to treat soil and groundwater in the northeastern area of the Site and downgradient vicinity and soil vapor within the SVE ROI, implementing an SSDS for the off-site area with a confirmed SVI concern, and associated monitoring and maintenance programs. Operation, maintenance, monitoring and certification costs are estimated at $3,600,800 (net present worth) for the estimated active remedial and monitoring periods. Post-remedial capital costs are estimated at $376,800 for the anticipated ends of the active remedial and monitoring periods. The net present worth of the recommended remedial alternative is $18,595,100 over a 30-year period and $12,230,600 over the estimated remedial and monitoring periods.

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Documents

FEASIBILITY STUDY REPORT · This Feasibility Study (FS) Report has been prepared by Goldberg Zoino Associates of New York, P.C. “Supplemental Remedial Investigative Report” (October