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Draft
Technical Plan for Pre-design NAPL Mobility and
Geotechnical Investigation Gowanus Canal
Brooklyn, New York
Prepared for
U.S. Environmental Protection Agency
June 2012
Prepared by
1
SECTION 1
Introduction The United States Environmental Protection Agency (USEPA) Region 2 completed a comprehensive Remedial Investigation (RI) in the Gowanus Canal. The results of this investigation (CH2M HILL, 2011a) indicated that Gowanus Canal sediments are impacted with Non‐Aqueous Phase Liquids (NAPL). A Feasibility Study (FS) of remedial alternatives for the Gowanus Canal (CH2M HILL, 2011) presented the following remedial action objectives (RAOs) for the NAPL‐impacted sediments:
Prevent the migration of NAPL into the canal after the remedial action is completed
Prevent NAPL from serving as a source of contaminants to groundwater discharging to the canal
This appendix presents an approach / technical plan to conduct pre‐design NAPL mobility, geotechnical, and general chemistry tests on soft and native sediments and conduct geotechnical tests on native sediments in the Gowanus Canal.
Specifically, Remedial Alternatives 5 and 7, evaluated in detail in the FS, included active capping of the entire canal. Active capping is expected to both control NAPL migration and reduce dissolve phase flux to the Gowanus Canal. Active capping can consist of a variety of process options which were discussed in the FS:
Isolation cap
Ebullition gas collection cap
Adsorptive cap
Reactive cap
Impermeable cap
For the FS, a combination of adsorptive and isolation cap was selected as the process option representative of active caps. All of the cap designs listed above can be considered in remedial design if active capping is a component of the final remedy. To select and design the appropriate cap, understanding NAPL behavior is critical.
This approach / technical plan is for performing pre‐design NAPL mobility, general chemistry, and geotechnical tests to support active capping pre‐design activities. The following steps are anticipated before active capping would be implemented:
Pre‐design testing
Design investigations
Pilot testing
Overlap with Other Planned Work In addition to this pre‐design NAPL mobility and geotechnical testing, USEPA plans to conduct a pre‐design bench scale testing to evaluate the application of in situ stabilization (ISS) on native sediments in the canal. The results from the pre‐design NAPL investigation would be considered together with the results from the pre‐design ISS bench scale test to evaluate where and how ISS can be applied on the native sediments to achieve the established RAOs.
2
SECTION 2
Data Quality Objectives The USEPA has developed the Data Quality Objectives (DQO) Process as the Agency’s recommended planning process when environmental data are used to select between two alternatives or derive an estimate of contamination. The DQO Process is used to develop performance and acceptance criteria (or data quality objectives) that clarify study objectives, define the appropriate type of data, and specify tolerable levels of potential decision errors that will be used as the basis for establishing the quality and quantity of data needed to support decisions. EPA has issued , Guidance on Systematic Planning Using the Data Quality Objectives Process (EPA QA/G‐4), to provide a standard working tool for project managers and planners to develop DQOs for determining the type, quantity, and quality of data needed to reach defensible decisions or make credible estimates. This guidance has been followed in developing this pre‐design NAPL testing approach / technical plan.
Establishing the DQOs consists of the processes presented in this approach / technical plan:
Problem Statement
Goals of Study
Identify Informational Inputs
Study Boundaries
Analytical Approach
Performance or Acceptance Criteria
Plan for Obtaining Data
Each of these DQO processes are discussed in the following sections.
Problem Statement The distribution of NAPL within the canal sediments was characterized during the RI based on visual impacts, but the impacts were not quantified. The geotechnical properties of the sediments were also not characterized, as this was considered a pre‐design task.
Pore fluid saturation of canal sediments is the relative fraction of total pore space containing a particular fluid (e.g., NAPL) in a representative volume of sediment. The mobility of NAPL is related to its saturation in the sediment. Residual saturation is the saturation level where a continuous NAPL becomes discontinuous and is immobilized by capillary forces. The magnitude of residual saturation is affected by several factors including pore‐size distribution, wetting properties of the fluids, interfacial tension, hydraulic gradients, buoyancy forces, and flow rates.
Establishing the residual saturation and current saturation of NAPL in canal sediments is important for assessing the potential mobility of the NAPL under the current canal conditions, and for designing remedial alternatives that meet the established RAOs.
Goals of Study The goals of the study are to perform NAPL saturation and mobility tests on NAPL impacted sediment in the canal to determine the sediment NAPL conditions, which combined with other environmental factors (i.e. groundwater discharge) could allow continued migration of NAPL into the canal. NAPL pore fluid saturations (PFS), NAPL drainage and inhibition (pressures to move NAPL and water through impacted sediment), and NAPL properties affecting buoyancy are the key parameters necessary for these assessments.
3
Identify Informational Inputs The information inputs necessary for this NAPL mobility study are:
NAPL impacts in soft and native sediment (pore fluid saturation)
Total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) impacts in soft and native sediment
Strength of native sediments
Hydraulic conductivity (permeability) of native sediments
NAPL and groundwater characteristics related to NAPL spreading and buoyant forces in the canal
Study Boundaries The study boundaries are the entire canal. Stations for the NAPL investigation were selected based on the severity of NAPL impacts present at the interface between native and soft sediments where there is high potential for NAPL migration.
Analytical Approach The approach that is being proposed for the Gowanus Canal Superfund site follows the approach for supplemental NAPL investigations outlined in A Decision Making Framework for Cleanup of Sites Impacted with Light Non‐Aqueous Phase Liquids (LNAPL) (EPA‐542‐R‐04‐011, March 2005).
Performance or Acceptance Criteria The specific Quality Assurance/Quality Control (QA/QC) requirements for the NAPL saturation/mobility testing will be provided in the project specific Quality Assurance Project Plan (QAPP). Reporting detection levels/target detection limits for general chemistry parameters will be presented in the QAPP. Reporting detection levels/target detection limits are not applicable for PFS analyses.
Plan for Obtaining Data Bulk soft sediment samples will be collected from fifteen locations described in this approach / technical plan. The bulk samples will be analyzed for average and maximum Semivolatile Organic Compounds (SVOC) and Volatile Organic Compounds (VOC) concentrations, and pore fluid saturations. Undisturbed, native sediment samples will be collected from fifteen locations described in this approach / technical plan. These undisturbed samples will be analyzed for hydraulic conductivity, unconfined compressive strength (UCS), NAPL pore fluid saturation, particle size distribution, and total VOC and SVOC concentrations.
4
SECTION 3
NAPL Mobility Technical Plan This section presents specific details for the following:
Experimental Design
Sample Locations
Sample Collection
Mobility Testing
Data Reporting
Figure 1 shows the Gowanus Canal and the station numbering nomenclature used in this document. The station numbers begin at 0+00 (0 feet) at the head of the canal and stop near 80+00 (8,000 feet) where Gowanus Bay makes its confluence with the Red Hook Channel. All sample locations are assigned a station number using this coordinate system.
Experimental Design The experimental design used data from the RI to identify a high and a low impact area for NAPL mobility testing.
From each area, samples are planned to accomplish the following:
Geotechnical characterization ‐ Undisturbed native sediment cores collected in Shelby Tubes will be analyzed for hydraulic conductivity and unconfined compressive strength (UCS) to determine baseline characteristics of the native sediment.
NAPL Mobility Testing – Undisturbed native sediment cores collected in Shelby Tubes will be sent to the laboratory for NAPL mobility testing. The goal of the NAPL mobility test program is to determine the distribution of NAPL within native sediments in the canal, determine how NAPL distribution relates to sediment particle size distribution, and determine whether PAH data can be used as an appropriate surrogate for NAPL saturation in determining NAPL distribution. Bulk soft sediment material will be collected at each location and sent to the laboratory for NAPL mobility testing. The goal of soft sediment NAPL testing is to determine the distribution of NAPL in soft sediments throughout the canal, and to determine if SVOC concentration can be used as a surrogate for NAPL saturation in determining distribution.
General Chemistry Testing – Bulk soft and native sediment samples will be sent to the laboratory for analysis of general chemistry parameters. The maximum‐impacted region of the soft and native sediment cores, based on visual observations, will be sub‐sampled and analyzed for maximum TPH and PAH concentrations. The remaining sediment from the core will be homogenized and the composite will be analyzed for average TPH and PAH concentrations. Composite native sediment samples will also be analyzed for pH, Atterberg limits, and total organic carbon. A composite of soft sediment from each transect will be analyzed for BTU value.
Figure 2 shows a flow chart of sample collection and an overview of the NAPL mobility testing.
Sample Locations NAPL impacts observed in soft and native sediment immediately above and below the soft/native sediment interface were evaluated to select the sample locations for NAPL saturation and mobility testing. Five transects were selected for testing. Figure 3 is a plan view of the canal showing the NAPL
5
impacts observed on either side of the sediment interface at each of the selected sample transects. Transects were selected to include minimal, medium, and high‐NAPL impacts in native sediments immediately below the soft/native sediment interface in order to bracket conditions throughout the canal.
Figure 4 shows a graph of the total PAH concentrations in native sediment in the main channel of the Gowanus Canal along with the locations of the five sample transects considered for the NAPL investigation and the two sample transects considered for the ISS bench scale test sample collection. The transects selected for the NAPL investigation were collocated or located very near the transects selected for ISS bench scale test sample collection, so the sampling events will be co‐located along transects 1 and 3.
Sample Collection At each transect, an initial sediment core will be collected from the soft sediment surface to five feet below the soft/native sediment interface for logging purposes. Cores will be collected by Vibracore or sonic drilling methods, and as such, are considered “bulk” samples and not undisturbed samples. During the logging process, geotechnical parameters will be measured using a Torvane and/or pocket penetrometer, as appropriate.
Based upon visual observations of each core, the most highly‐impacted region of the soft sediment will be collected as a sub‐sample for TPH and PAH analyses. The most impacted region of the soft sediment will also be collected for pore fluid saturation (PFS) analysis. The remaining soft sediment material across the core will be homogenized and sub‐sampled for analysis of TPH, PAHs, pH, and total organic content (TOC). Additionally, a sub‐sample of the homogenized soft sediment material will be submitted for NAPL PFS analysis.
The most highly‐impacted region of the native sediment will be collected as a sub‐sample for analysis of TPH. The remaining native sediment material across the core will be homogenized and sub‐sampled for analysis of TPH, pH, TOC and Atterberg limits.
After all three cores on a given transect are collected, some of the homogenized soft sediment material from each of the three cores will be homogenized together to form a homogenized transect sample for BTU determination.
At each core location, as close as practical to the original core, three additional co‐located cores will be advanced into native sediment in order to collect undisturbed geotechnical and NAPL mobility samples (see Figure 2). These cores will extend from the soft‐native sediment interface to five feet below the interface. The collection of undisturbed Shelby Tube samples is necessary for these parameters. A drill rig capable of advancing the Shelby Tubes ahead of the sonic drill casing using a hydraulic press will be utilized. Further details are provided below on the specific types of samples to be collected.
One undisturbed sample in a Shelby tube from each sample location will be shipped to the laboratory for geotechnical analysis. The remaining undisturbed sample from each sample location will be frozen on dry ice, and shipped overnight to the laboratory for NAPL mobility analysis.
Laboratory NAPL Mobility Test Program Native Sediment Geotechnical Characteristics Samples will be analyzed for the geotechnical parameters specified in Table 1. The basis for the selection of particular analytes is described below:
6
Unconfined compressive strength analysis will provide information allowing assessment of the ability of the untreated native sediment material to structurally support installation of an active cap.
Hydraulic conductivity (permeability) analysis will provide information on the potential for transport of NAPL and dissolved contaminants from canal native sediments into the surface water.
Atterberg limits analysis will provide information on the liquid limit and plastic limit of the canal native sediments. These properties relate to the compressibility, permeability, and strength of the native sediments and this data will aid in determining their suitability as a base for a cap.
NAPL Saturation and Mobility Samples will be analyzed for the NAPL saturation/mobility parameters specified in Table 1. The basis for the selection of particular analytes is described below:
Two soft sediment samples will be collected from the bulk sediment at each sample location. One is a sub‐sample collected from the most highly‐impacted interval of the soft sediment core, based on visual observations. The second is from a composite of the remaining soft sediment from the given sample location. These samples will be used for determination of pore fluid saturation in the soft sediment. Since the samples are disturbed, NAPL drainage tests will not be performed on these samples. The bulk density, total porosity, and particle density of these samples will also be determined as part of the PFS calculation.
One undisturbed sample / core is required from the native sediment at each boring location, to a depth of 5 feet below the soft/native interface. The undisturbed sample / core will be collected in Shelby Tubes. These undisturbed cores will be frozen and shipped on dry ice to the laboratory. The cores will be cut into 2 inch sub‐samples, and one sub‐sample from each foot of core length will be analyzed for PFS, bulk density, total porosity, particle density, and particle size distribution. These tests will help correlate NAPL saturation with sediment particle size distribution. In addition to PFS analyses, selected intervals of the cores will be analyzed for NAPL drainage, a key factor for NAPL mobility. The intervals will be selected based on visual observations and ultraviolet photography in the laboratory. Since these samples are expected to be completely saturated with water and/or NAPL (no air), drainage will be analyzed via the water‐flood method and NAPL‐flood method (API, 1998) as opposed to centrifugal methods. Together, these analyses will provide quantitative information on the potential mobility of NAPL present in canal sediments relative to the existing degree of saturation and under the anticipated hydraulic driving forces present in the canal.
As part of the complete NAPL mobility package, samples of groundwater and NAPL will be collected in 1 L glass jars from upland recovery wells with NAPL present. These samples will be analyzed for density, viscosity, and interfacial tension. These parameters provide additional information to be used in the assessment of potential NAPL mobility in the canal.
General Chemistry Samples will be analyzed for the general chemistry parameters specified in Table 1. The basis for the selection of particular analytes is described below:
TOC analysis will provide information related to the potential of biogenic gas production and transport of NAPL by ebullition. The Lloyd Kahn method will be used for this analysis since it is specific to sediments while the ASTM method (D2974) is more specific to soils. A homogenized sample of native sediment from each sample location will be submitted for TOC analysis via the Lloyd Kahn method.
7
In order to make determinations of potential disposal options for dredged material, the thermal value of the soft sediment will be determined. A homogenized sample of soft sediment from each transect will be submitted for BTU analysis via method ASTM D240.
Samples from the soft and native sediment will be analyzed for gasoline‐range, diesel‐range, and oil‐range TPH. Previously collected samples were analyzed for TPH, but not for PFS. Running both analyses on these new samples would potentially allow for development of a correlation between the two parameters, providing for a rough calculation of PFS in the previously collected samples based on TPH results. A sample from the most highly‐impacted interval based on field observation of NAPL impacts at each location and a homogenized sample of soft sediment from each sample location will be submitted for TPH analysis by method SW8015.
Samples from the soft and native sediment will be analyzed for PAHs. The results will be used for comparison to previously collected samples and for assessment of potential leachability. A sample from the most highly‐impacted interval based on field observation of NAPL impacts at each location and a homogenized sample of soft sediment from each sample location will be submitted for PAH analysis by method SW8270.
Samples from the native sediment will be analyzed for pH. The results will be used for comparison to previously collected samples and for assessment of potential leachability. A homogenized sample of native sediment from each sample location will be submitted for pH analysis by method E150.1.
Data Reporting Mobility test results will be used to estimate residual saturation in canal sediments. This data will be used to estimate volumes (affected sediment, NAPL, pore space, and NAPL above residual saturation). The NAPL saturation data will be compared to current and historical TPH and PAH data to assess whether TPH or PAH concentration can be used as an acceptable surrogate parameter for NAPL saturation.
A technical memorandum will be prepared summarizing the NAPL saturation and mobility assessment findings after completion of the tests.
8
Table 1 Analytical and Sample Size Requirements Gowanus Canal Superfund Site Analysis Sediment Layer Method Collection
Method Volume Requirement
NAPL Mobility
Pore Fluid Saturation (maximum and average) (includes: Bulk density [wet and dry], Total Porosity, and Particle Density)
Soft Dean‐Stark, API, 1998
Bulk 8 oz. jar
Pore Fluid Saturation (includes: Core cutting, Core photography, Bulk density [wet and dry], Total Porosity, Particle Density, and Particle size analysis)
Native Dean‐Stark, API, 1998
ASTM 5079
ASTM D422
Undisturbed 3x36” Shelby Tube – collect from sediment interface to five feet below interface
NAPL Mobility (includes: Water‐flood method and NAPL‐flood method)
Native API, 1998 Undisturbed 3x36” Shelby Tube – collect from sediment interface to five feet below interface
Fluid Viscosity NAPL/Groundwater ASTM D445 Grab sample from recovery well
1 L
Fluid Density NAPL/Groundwater ASTM D1217 Grab sample from recovery well
NA – included in viscosity volume
Interfacial Tension NAPL/Groundwater ASTM D971 Grab sample from recovery well
NA – included in viscosity volume
Geotechnical
Strength Soft/Native Pocket Penetrometer
Bulk NA – performed during core logging
Strength Soft/Native Torvane Bulk NA – performed during core logging
Unconfined Compressive Strength – as‐received material
Native ASTM D2166 Undisturbed 3x36” Shelby Tube – collect from sediment interface to five feet below interface
Hydraulic Conductivity – as‐received material
Native ASTM D5084 Undisturbed 3x36” Shelby Tube – collect from sediment interface to five feet below interface
Atterberg Limits Native ASTM D4318 Bulk 8 oz /location
General Chemistry
Calorimetry (average) Soft ASTM D240 Bulk 4 oz /transect
TPH‐D,R,O (maximum) Soft/Native SW 8015‐D/ SW8015‐G/ SW‐8015‐RRO
Bulk 6 oz /location /sediment type
9
Analysis Sediment Layer Method Collection Method
Volume Requirement
PAHs (maximum) Soft/Native SW 8270 Bulk 8 oz /location /sediment type
PAHs (average) Soft/Native SW 8270 Bulk 8 oz /location /sediment type
pH (average) Native E150.1/SM4500‐HB/ SW9045C
Bulk 4 oz /location
TOC (average) Native Lloyd Kahn Bulk 4 oz /location
.
0+00
23+00
56+25
4th Street Turning
Basin
7+00
4th Street Turning Basin
Junction
25+00
6th Street Turning
Basin Junction
36+00
6th Street
Turning Basin
8+00
7th Street Turning
Basin Junction
40+00
7th Street Turning
Basin
5+00
62+25
80+00
(8,000 feet)
RTA 1RTA 2
RTA 3a Creamer Street to
Sigourney Street
RTA 3b Sigourney Street to Redhook Channel
Coordinates of turning basins at canal intersection 0+00
FIGURE 1Gowanus Canal Station NumberingGowanus Canal NAPL InvestigationBrooklyn, New York
Native Sediment
Soft Sediment
Ele
vati
on
(fe
et N
AV
D8
8 A
pp
roxi
mat
e)
10 ft
0 ft
-10 ft
-20 ft
-30 ft
-40 ft
Barge
Grab SamplePFS, TPH, PAHs
Composite Sample from Core
PFS, TPH, PAHs
Composite Sample from Transect
BTU Value
Undisturbed CoreNAPL Mobility Package
Bulk Soft Sediment
Bulk Native Sediment
Native Sediment(3" Shelby Tube)
Native Sediment(3" Shelby Tube)
Grab SampleTPH, PAHs
Composite Sample from Core
TPH, PAHs, pH, Atterberg
Limits, TOC
Undisturbed CoreStrength, Permeability
(ISS Testing)
Three Locations per TransectThree Cores per Location
Log CorePocket Pen., Vane Shear
Log CorePocket Pen., Vane Shear
Upper 5 feet of Native
FIGURE 2NAPL Mobility Sample Collection Gowanus Canal NAPL InvestigationBrooklyn, New York
Legend
Proposed Sampling Transect
NAPL impacts listed are Soft/Native sediment immediately to either side of sediment interfaceNI = No NAPL impacts observedCSB = Coating, staining, or blebs observedS = NAPL Saturated
0+0023+00
56+2562+2580+00
(8,000 feet)
RTA 1RTA 2
RTA 3a Creamer Street to
Sigourney Street
RTA 3b Sigourney Street to Redhook Channel
Coordinates of turning basins at canal intersection 0+00
FIGURE 3Gowanus Canal Transect MapGowanus Canal NAPL InvestigationBrooklyn, New York
Transect 5
GC-SD76C
near 66+49
CSB/CSB
Transect 4
GC-SD64D
near 51+61
CSB/S
Transect 2
GC-SD11A
near 07+60
NI/NI
Transect 1
GC-SD152
near 03+94
S/CSB
Transect 3
GC-SD44A
near 35+40
S/S
Metro MGP Fulton MGPCG/PP MGP
0
0
0
1
10
100
1,000
10,000
100,000
010002000300040005000600070008000
Total PAH (mg/kg)
Distance from Head of Canal (feet)
Native Sediment ‐Main Channel Native Sediment ‐ Transects 1‐5 ISS Sample Locations
Gowanus Expy 9th Street 3rd Street
Transect 5near 66+49
Transect 4near 51+61
Transect 2near 07+60
Transect 1near 03+94
Transect 3near 35+40
Metropolitan MGP FultonMGPCG/PP MGP
FIGURE 4PAH Concentrations in Native Sediments Along Gowanus CanalGowanus Canal NAPL InvestigationBrooklyn, New York