Final Construction Completion Report

Report Template w/Numbered HeadingsFinal Construction Completion Report
Prepared for:
Georgia-Pacific LLC
Prepared by:
ARCADIS G&M of Michigan, LLC 10559 Citation Drive Suite 100 Brighton Michigan 48116 Tel 810.229.8594 Fax 810.229.8837
Our Ref.:
B0064536.0002.00675
Date:
February 25, 2011 This document is intended only for the use of the individual or entity for which it was prepared and may contain information that is privileged, confidential and exempt from disclosure under applicable law. Any dissemination, distribution or copying of this document is strictly prohibited.
Stephen Garbaciak Jr., P.E. Vice President Michael J. Erickson, P.E. SRI/FS Project Coordinator
Table of Contents
1. Introduction 1-1
1.1 General 1-1
1.2 Project Area Description 1-2
1.3 Overview of Response Actions and Summary of Work Performed 1-3
1.4 Scope of the Completion Report 1-5
1.5 Report Organization 1-6
2. Project Overview 2-1
2.1 Project Organization 2-1
2.3 Deviations from the Design Report 2-3
2.3.1 Backfilling of Excavated Areas 2-3
2.3.2 Removal Area 5 2-4
2.3.3 Habitat Reconstruction Plant Species 2-4
2.3.4 Oxbow Removal 2-5
2.3.4.2 Removal Footprint 2-6
3. Removal Activities 3-1
3.2.2 Permitting 3-2
3.2.5 Mobilization and Project Area Preparation 3-3
3.2.5.1 Access Road Construction 3-4
3.2.5.2 Staging Area Construction 3-5
3.2.5.3 Installation of Erosion Controls 3-6
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Table of Contents
3.3.1 Turbidity Curtains 3-7
3.3.3.1 Turbidity Monitoring 3-8
3.4 Soil and Sediment Removal 3-11
3.4.1 Excavation Confirmation 3-12
3.4.1.2 Confirmation Sampling 3-14
3.4.2 Removal Areas 3-14
3.4.2.3 Island Removal Areas 3-17
3.4.2.4 Confirmation Sampling Surveying and Analytical Data 3-17
3.4.3 2009 Removal Activities 3-17
3.4.3.1 Clearing and Grubbing 3-17
3.4.3.2 Removal Area 1 3-18
3.4.3.3 Removal Area 2 3-18
3.4.3.4 Removal Area 3A 3-19
3.4.3.7 Island 1 3-20
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Table of Contents
3.4.4.6 Island 2 3-25
3.4.4.7 Oxbow Area 3-26
3.5.1 Dry Soil Mixing 3-31
3.5.1.1 Solidification Agents 3-31
3.5.2 Water Treatment 3-31
3.6 Transportation and Disposal of Sediment and Soil 3-35
3.7 Bank Stabilization and Habitat Reconstruction 3-35
3.7.1 Bank Stabilization Materials 3-36
3.7.1.1 Backfill 3-36
3.7.1.3 Coir Log 3-37
3.7.1.5 Topsoil 3-37
3.8.1 Restoration of Disturbed Vegetation 3-42
3.8.2 Access Roads and Staging Areas 3-42
3.8.3 Contractor Demobilization 3-44
3.8.5 Individual Node Sample Submittal 3-44
3.9 Summary 3-45
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Table of Contents
5. Summary 5-1
6. References 6-1
Table 2 Summary of Pre- and Post-Construction Sampling Analytical Results
Table 3 Staging Area Size and Operating Dates (in text)
Table 4 Summary of Surface Water Sampling Analytical Results
Table 5 Summary of Confirmation Sampling Analytical Results
Table 6 Water Treatment System Period of Use (in text)
Table 7 Summary of Wipe Sampling Analytical Results
Table 8 Discharge Monitoring Parameters (in text)
Table 9 Summary of Water Treatment Sampling Analytical Results
Table 10 Status of Access Roads (in text)
Table 11 Summary of Individual Node Sampling Analytical Results
Table 12 Summary of Removal and Habitat Reconstruction Activities (in text)
Figures
Figure 2 Site Plan
Figure 4.1 Excavation Site Layout (11+25 to 21+75)
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Table of Contents
Figure 5.1 Excavation Cross-Sections 1 to 14
Figure 5.13 Excavation Cross-Sections 203 to 210 and 219 to 224
Figure 5.16 Excavation Cross-Sections OX1 to OX13
Figure 5.17 Excavation Cross-Sections OX14 to OX25
Figure 6.1 Confirmation Sampling Removal Area 6
Figure 6.2 Confirmation Sampling Oxbow Removal Area
Figure 6.3 Confirmation Sampling Removal Area 5B Floodplain
Figure 6.4 Confirmation Sampling Removal Area 5B
Figure 6.5 Confirmation Sampling Removal Area 4B
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Table of Contents
Figure 6.7 Confirmation Sampling Island 2
Figure 6.8 Confirmation Sampling Removal Area 4A and 5A
Figure 6.9 Confirmation Sampling Removal Area 3A
Figure 6.10 Confirmation Sampling Removal Area 2
Figure 6.11 Confirmation Sampling Removal Area 1 and Island 1
Figure 7 Water Treatment Process Flow Diagram
Figure 8.1 Restoration As-Built (11+25 to 21+75)
Figure 8.3 Restoration As-Built (Oxbow)
Figure 8.8 Restoration Notes and Specifications
Figure 9 Canoe Portage As-Built
Appendices
Appendix B Photographic Record
Appendix D Material Specifications
Appendix F Turbidity Monitoring Records
Appendix G RTK GPS Calibration Logs
Appendix H Water Treatment Logs
Appendix I Waste Manifests
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Table of Contents
AOC Administrative Settlement Agreement and Order of Consent BBL Blasland, Bouck, and Lee, Inc. CERCLA Comprehensive Environmental Response, Compensation, and Liability
Act CKD cement kiln dust CQA construction quality assurance cy cubic yards HDPE high-density polyethylene iSIC Intelligent Sensor Interface & Control MDEQ Michigan Department of Environmental Quality MDNR Michigan Department of Natural Resources MDNRE Michigan Department of Natural Resources and Environment mg/kg milligrams per kilogram mg/L milligrams per liter µg/L micrograms per liter MHLLC Millennium Holdings, LLC NAD 83 North American Datum 1983 OSC On-Scene Coordinator PCBs polychlorinated biphenyls QAPP Quality Assurance Project Plan RTK GPS real time kinematic global positioning system sf square feet SRD Substantive Requirements Document SRI/FS Supplemental Remedial Investigation/Feasibility Study TAL Test America Laboratories TCL target compound list TCRA time-critical removal action TIN triangular irregular network TSS total suspended solids USACE United States Army Corps of Engineers USEPA United States Environmental Protection Agency USFWS United States Fish and Wildlife Service
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Plainwell No. 2 Dam Area TCRA Final Construction Completion Report
Statement by Supervising Contractor
I am a registered Professional Engineer and represent ARCADIS as the Supervising Contractor for work conducted by Georgia-Pacific LLC for the Allied Paper, Inc./Portage Creek/Kalamazoo River Superfund Site Plainwell No. 2 Dam Area Time-Critical Removal Action. This report is submitted in accordance with Paragraph 20 of the June 2009 Administrative Settlement Agreement and Order on Consent for Removal Action (Docket No. V-W-09-C-925).
Under penalty of law, I certify that to the best of my knowledge, after appropriate inquiries of all relevant persons involved in the preparation of the report that the information submitted is true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations
____________________________ Stephen Garbaciak Jr., P.E. Supervising Contractor ARCADIS G&M of Michigan, LLC
Date: February 2011
1. Introduction
This Plainwell No. 2 Dam Area TCRA Final Construction Completion Report (Completion Report) has been prepared on behalf of Georgia-Pacific LLC (Georgia-Pacific) to summarize the efforts associated with the time-critical removal action (TCRA) conducted in the Plainwell No. 2 Dam Area located along the Kalamazoo River near Plainwell, Michigan. The TCRA was completed in accordance with the Administrative Settlement Agreement and Order of Consent for Removal Action, Docket No. V-W-09-C-925 (AOC), dated June 8, 2009 (United States Environmental Protection Agency [USEPA] 2009a). Work activities in support of the TCRA were completed from August 2009 through October 2010.
1.1 General
On February 21, 2007 Georgia-Pacific and Millennium Holdings, LLC (MHLLC) voluntarily entered into an AOC with USEPA. This agreement, which described a series of supplemental remedial investigations and feasibility studies (SRIs/FSs) to be carried out at the Allied Paper, Inc./Portage Creek/Kalamazoo River Superfund Site (Site or Superfund Site), is referred to as the SRI/FS AOC (Comprehensive Environmental Response, Compensation, and Liability Act [CERCLA] Docket No. V-W-07-C-864). On February 5, 2009, MHLLC notified USEPA in writing that they would not be participating in any further work on the Site from that date forward, as a result of the Lyondell Chemical Company (Lyondell) bankruptcy. An outcome of the bankruptcy process was that Lyondell was released of responsibility for continued work on the Kalamazoo River by the United States in exchange for a cash settlement that included approximately $49.5 million for river-related work.
The SRI/FS work conducted to date has been focused in Area 1 of the Site – defined as the reach of the Kalamazoo River between Morrow Dam and the Plainwell Dam and a stretch of Portage Creek – as described in the USEPA-approved Supplemental Remedial Investigation/Feasibility Study Work Plan – Morrow Dam to Plainwell Dam (Area 1 SRI/FS Work Plan; ARCADIS BBL 2007a). After reviewing the results of sampling and investigation work in the Plainwell No. 2 Dam Area completed pursuant to the Area 1 SRI/FS Work Plan (ARCADIS BBL 2007a), USEPA determined that a TCRA was necessary to address areas that may represent potential sources of polychlorinated biphenyls (PCBs) to the river. Locations targeted included bank soils, sediments in a portion of a historical oxbow channel, and soils in a floodplain area adjacent to the oxbow.
The Plainwell No. 2 Dam Area Time-Critical Removal Action Design Report (Design Report) (ARCADIS 2009a) provided a detailed description of the TCRA, including contract drawings and associated specifications followed during implementation of the remedial design in
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accordance with the AOC (USEPA 2009a). The Design Report (ARCADIS 2009a) was submitted to USEPA in July 2009, approved on July 24, 2009 (USEPA 2009b), and served as the work plan for removal activities.
This Completion Report is designed to satisfy the requirements of Paragraph 20 of the AOC (USEPA 2009a) and provide USEPA with documentation that the actions described in the AOC are complete.
1.2 Project Area Description
The Plainwell No. 2 Dam Area is located on the Kalamazoo River approximately 3.5 miles upstream of the former Plainwell Dam in the city of Plainwell and Gun Plain Township, Allegan County (Figure 1).
As described in Section 1.3 of the Design Report (ARCADIS 2009a), the Plainwell No. 2 Dam consists of four separate remnant structures—a waste gate structure (located approximately one mile downstream of the project area), a right diversion structure, a left diversion structure, and a head gate structure — all of which were initially constructed in 1856 by the Plainwell Water Power Company1. Earthen embankments, approximately 2,520 feet in total length, are also present to connect the two diversion structures. The right and left diversion structures consist of concrete spillway gate bays and a concrete spillway, respectively, although no gates remain in the right diversion structure. An earthen embankment connects the left abutment of the left diversion structure and the head gate structure (United States Army Corps of Engineers [USACE] 1979). The diversion structures direct water from the main stem of the river into a mill race/power canal that was once used to generate electric power for a flour mill, the City of Plainwell, and several other businesses.
The head gate and waste gate structures in the power canal were formerly used to regulate the head and discharge through the powerhouse. The head gate structure consists of a concrete spillway with no control devices. The waste gate structure consisted of two sluice ways for which the gates are no longer in place (USACE 1979).
The Plainwell No. 2 Dam structures did not significantly alter the shape or surface area of the river, nor did they create lake-like impoundments as in the case of the former hydroelectric dam construction in downstream areas. They did, however, alter flooding characteristics of the river to some degree upstream.
1 Documentation of any subsequent construction activities is not available.
According to the Michigan Department of Environmental Quality (MDEQ) (now the Michigan Department of Natural Resources and Environment [MDNRE]), the dam and associated structures were partially removed in the early 1980s such that there is no longer any “significant amount of water” (Hayes 1998a) impounded in the area. The waste gate structure’s lift gate and stoplog guides were still present in 1980, and at that time there were no active operational procedures in place other than to permanently leave all discharge control structures adjusted so that they would permit maximum discharge capacity (USACE 1979). It was the opinion of the Michigan Department of Natural Resources (MDNR) (now MDNRE) that the dam structures “will not significantly impound any water that would pose a hazardous condition to the public safety” (Cook 1980).
In 1979, the Plainwell No. 2 Dam was classified as a small size dam with high hazard potential in accordance with the National Dam Safety Program Criteria (USACE 1979). Following the partial removal of the dam and associated structures in the 1980s, the dam was reclassified as a low hazard potential (Hayes 1998b). The primary continuing purpose of the remaining structures is to maintain flow through the mill race/power canal, which along with the Kalamazoo River, encircles the city of Plainwell and gives it the name “Island City.” State and local officials have expressed intentions to leave the Plainwell No. 2 Dam structures in place to continue to provide flow through the mill race and preserve the character of the city.
As described in Section 1.4 of the Design Report (ARCADIS 2009a), the Plainwell No. 2 Dam Area has been the focus of a series of investigations by ARCADIS (formerly known as Blasland, Bouck & Lee, Inc [BBL] and ARCADIS BBL), MDEQ (now MDNRE), and USEPA since 2000. The most recent PCB data were collected during a sampling effort conducted by ARCADIS between 2008 and 2009. A variety of targeted studies of the impoundment were also conducted in 2008 and 2009 to further characterize project area topography, bank stability/disposition, flow hydrodynamics, equipment accessibility, and habitat quality.
1.3 Overview of Response Actions and Summary of Work Performed
The activities completed at the Plainwell No. 2 Dam Area were consistent with the requirements of the Design Report. In summary, the TCRA was performed to achieve the following objectives set forth in the Design Report (ARCADIS 2009a):
1. Stem the potential loading of PCBs to the Kalamazoo River from river banks in the Plainwell No. 2 Dam Area.
2. Remove sediments located at the mouth of and along the western side of the former oxbow channel.
3. Dispose removed PCB-containing bank soils and sediment in a way that does not present unreasonable risk to human health or the environment.
4. Mitigate potential adverse environmental impacts of construction.
5. Complete habitat enhancement to potentially address past releases of PCBs from Georgia- Pacific facilities – the Natural Resource Trustees will determine if and to what degree these enhancements may compensate for natural resource injuries in the project area.
To accomplish these objectives, the removal action in the Plainwell No. 2 Dam Area included the following specific elements of work:
a) Removal of a defined area of sediments at the mouth of and along the western side of the former oxbow channel which yielded samples with elevated PCB concentrations as described in Section 2.2 of the Design Report (ARCADIS 2009a).
-- See Section 3.4 for a description of the removal operations.
b) Removal of PCB-containing bank soils, with bank cutbacks to stable slopes and backfill of the removal areas to original grade where appropriate. Some areas were not fully backfilled to encourage redevelopment of native habitat. The full range of restoration options are outlined in Contract Drawings R-1.1 through R-1.7.
-- See Sections 3.4.3, 3.4.4, and 3.7 for a summary of how the materials were removed and backfilled.
-- See Section 3.4.1 for a summary of how excavation limits were confirmed.
c) Disposal of PCB-impacted sediments and soils in licensed commercial landfills.
-- See Section 3.6 for a description of how the excavated materials were disposed.
d) Mitigate potential adverse effects of construction.
-- See Section 3.2 for a description of the Indiana bat survey, air monitoring, and erosion control.
-- See Section 3.3 for a description of resuspended sediment control.
-- See Section 3.5 for a description of water treatment.
-- See Section 3.6 for a description of soil and sediment transportation.
e) Complete habitat enhancement to potentially address past releases of PCBs from Georgia- Pacific facilities.
-- See Section 3.7 for a description of restoration activities.
Construction activities performed to achieve these objectives are described in the sections referenced after each bullet point.
1.4 Scope of the Completion Report
This Completion Report describes the completed response actions at the Plainwell No. 2 Dam Area and contains the following information:
• Material testing and certification results
• Sediment and soil removal narrative
• Waste disposal manifests
• Confirmation sample results
• Final sediment excavation elevations, documented on as-built cross-sections with elevations referenced to the appropriate vertical datum
• Daily activity logs, which include equipment calibration records, air monitoring records, construction dewatering, sediment/soil drainage, water treatment records, and daily weather conditions
• Turbidity monitoring records
• A good faith estimate of total project cost
• Certification by the Supervising Contractor that based on the Supervising Contractor’s knowledge and review of the construction records, the construction met the requirements of the engineering plans
The scope of this Completion Report is limited to the activities necessary to complete the TCRA.
1.5 Report Organization
The remainder of this Completion Report is organized into five sections. A brief overview of each of the subsequent sections is presented below.
• Section 2 – Project Overview; describes the project organization, provides a summary of the work performed, and describes deviations from the Design Report (ARCADIS 2009a).
• Section 3 – Removal Activities; presents a summary of activities for each element of the project.
• Section 4 – Post-Removal Controls; describes post-construction activities focusing on several aspects of the work, including monitoring of the banks and revegetation efforts.
• Section 5 – Summary; summarizes how the removal activities achieved the objectives set forth in the Design Report.
• Section 6 – References; lists documents used in preparation of this Completion Report.
Tables, figures, and appendices are also included to provide further detail, as appropriate.
2. Project Overview
This section describes the project organization, provides a summary of the work performed and the performance standards for the TCRA, and describes deviations from the Design Report (ARCADIS 2009a).
2.1 Project Organization
Several organizations were responsible for completion of the TCRA in the Plainwell No. 2 Dam Area. These organizations and their associated roles and responsibilities are described below.
Georgia-Pacific entered into the AOC and was responsible for performing the TCRA in the Plainwell No. 2 Dam Area.
USEPA signed the AOC with Georgia-Pacific and provided oversight and documentation of construction activities. Design changes and construction issues were discussed with USEPA, as necessary. USEPA consulted with other government agencies as necessary, including, but not limited to the United States Fish and Wildlife Services (USFWS), MDNRE (formerly MDNR and MDEQ), and the National Oceanic and Atmospheric Administration.
ARCADIS served as the Supervising Contractor for the project. In this role, ARCADIS implemented the TCRA on behalf of Georgia-Pacific and provided full-time construction management and construction quality assurance (CQA) services for the duration of removal activities. ARCADIS documented that the TCRA was implemented in conformance with the approved work plan (the Design Report [ARCADIS 2009a]), documented progress towards meeting design objectives, recorded daily work activities, performed construction monitoring, directed subcontractors, provided health and safety oversight, and approved field changes.
ARCADIS appointed a CQA Observer who was responsible for daily construction oversight to verify that the construction was performed in general conformance with the Design Report (ARCADIS 2009a). CQA also included observation, testing, and documentation of certain construction phases on a periodic basis to verify conformance with the approved guidance and design documents. The CQA Observer reviewed pre-removal submittals and conformance test results and prepared Daily Construction Reports with photographs to communicate the project’s progress to the project team throughout the course of construction.
The CQA Observer identified and documented construction problems or deficiencies and discussed them with the Supervising Contractor (who had ultimate technical responsibility for the work performed), as necessary, and related parties as required to implement corrective
action. A team of environmental and geotechnical engineers and other experts, as appropriate, provided engineering and construction support and management. Corrective actions to resolve problems or deficiencies were implemented by subcontractors and observed and documented by the CQA Observer. Significant problems and corrective actions are discussed in Section 2.3. On a daily basis, the CQA observer documented and corrected, if necessary, actions including, but not limited to excavation depth confirmation, sampling procedures and results, restoration methods, re-suspension control effectiveness, and survey data collection.
ARCADIS retained various subcontractors to perform construction activities associated with the TCRA. Terra Contracting, LLC of Kalamazoo, Michigan was selected as the primary removal contractor and was responsible for support facilities and access road construction, soil and sediment excavation activities, installation of resuspended sediment controls, construction dewatering and water treatment, management of waste transport and disposal, and restoration of excavated areas. American Environmental Group of Richfield, Ohio installed geotextile fabric and liner at the staging areas, and JF New of Walkerton, Indiana revegetated the excavated and restored areas. Subcontractors retained other firms, as necessary, to complete their scope of work.
2.2 Summary of Work Performed
The following activities (described further in Sections 3.2 through 3.8) were completed to achieve the objectives of the TCRA, as described in Section 1.3:
• Completion of pre-construction activities
• Dewatering, processing, and treatment, as necessary, of excavated materials
• Transportation and disposal of sediments and soils
• Bank stabilization and habitat reconstruction
• Project area restoration and demobilization
The TCRA was completed from August 2009 through October 2010. The 2009 construction season was completed from August through December 2009. The 2010 construction season was completed from January through October 2010. Removal activities were suspended from November 2009 through May 2010. During that time equipment and materials were removed
from the north side of the river and remobilized to the south side of the river. Project area preparation was performed on the south side of the river, and demobilization and restoration activities were performed on the north side of the river.
2.3 Deviations from the Design Report
Work activities that deviated from the Design Report were performed due to unexpected conditions encountered in the field or at the request of the regulatory agencies. All changes were discussed by the Supervising Contractor and USEPA prior to implementation, and were documented by the CQA Observer and through correspondence with the regulatory agencies. The text of the Design Report was not modified. Specific deviations from the Design Report are discussed below.
2.3.1 Backfilling of Excavated Areas
As operations were completed within a removal area, the banks were reconstructed to a stable condition and revegetated. Restored banks were backfilled to the specific design elevations, graded, and provided with toe protection, where appropriate, to minimize bank erosion and allow bank access for semi-aquatic wildlife. Typical restored bank cross-sections and planned bank restoration techniques were provided on Contract Drawings R-2.1 and R-2.2 and R-1.1 through R-1.7, respectively, of the Design Report (ARCADIS 2009a).
According to Section 2.10 of the Design Report (ARCADIS 2009a), of primary importance for final bank elevation was the relationship of the restored bank elevation to the corresponding elevation of the opposite bank. When the opposing bank was lower or banks were at a similar elevation, this elevation controlled the frequency and duration of inundation. Therefore, maintaining the final bank elevation at or above the same elevation as the opposite bank was critical to maintaining the frequency and duration of inundation in floodplain wetlands as the river water level rises with storm flows. However, the final elevation of disturbed high banks provided some flexibility in final elevations as long as the higher bank remained the higher bank. Disturbed high banks could be left at post-excavation elevations if that elevation remained higher than the low bank. Figure 2-7 of the Design Report (ARCADIS 2009a) illustrated where these different relationships occur in the Plainwell No. 2 Dam Area.
Using this as direction, ARCADIS, in consultation with USEPA, determined that backfilling to pre-excavation elevations was not warranted in all areas. As such, actual restoration activities deviated from the plan established in Contract Drawings R-1.1 through R1.7 and R-2.1 and R- 2.2 of the Design Report (ARCADIS 2009a). Restoration activities and construction of stable banks focused on maintaining the elevation relationship between opposing banks more so than
re-building the bank to its pre-construction elevation. Backfill was used when necessary to preserve the relationship between opposing banks (i.e. the higher bank remained the higher bank), and topsoil was installed as necessary in areas where post-excavation soil composition would not support vegetation growth. Additional information regarding restoration activities is included in Section 3.8.
2.3.2 Removal Area 5
Visual observations in the downstream portion of Removal Area 5 revealed a guy wire used to support the high-tension power lines crossing the Kalamazoo River near the right diversion structure. In order to avoid compromising the integrity of the guy wire, the excavation limits of Removal Area 5 were modified to provide a 25-foot offset from the guy wire. In addition, at the request of USEPA, a canoe portage was designed and installed at the downstream end of Removal Area 5. These modifications were approved by USEPA on October 14, 2009 (USEPA 2009c). See Section 3.7.3 for additional information.
2.3.3 Habitat Reconstruction Plant Species
The species to be used for re-vegetation are described in Section 3.7 and Contract Drawing G- 5.2 of the Design Report (ARCADIS 2009a). Through discussions with the habitat reconstruction subcontractor, ARCADIS determined that some tree, shrub, and grass species scheduled to be planted as a part of habitat reconstruction activities on the north side of the river would not be available. The planting plan was revised to reflect available tree and shrub species. The following modifications to the planting plan were made:
2009 Construction Season
• Rice Cutgrass was included in the emergent wetland and forested wetland seed mix instead of American Slough Grass.
• Panicled Aster was included in the emergent wetland and forested wetland seed mix instead of New England Aster.
• Heath Aster was included in the forested upland seed mix instead of Annual Rye.
• Bottlebrush Grass was included in the forested upland seed mix instead of Thickspike Wheatgrass.
• Troublesome Sedge was included in the forested upland seed mix instead of Plains Oval Sedge.
• Swan’s Sedge was included in the forested upland seed mix instead of Sand Bracted Sedge.
• Prairie Junegrass was included in the forested upland seed mix instead of Junegrass.
• Prairie Dropseed was included in the forested upland seed mix instead of Sand Dropseed.
• Prairie Milkweed was included in the forested upland seed mix instead of Common Milkweed.
• Few Leaf Sunflower was included in the forested upland seed mix instead of Tall Coreopsis.
• Prairie Cinquefoil was included in the forested upland seed mix instead of Flowering Spurge.
• Canadian Milkvetch was included in the forested upland seed mix instead of American Vetch.
• Swamp Rose and Black Willow were planted instead of Speckled Alder.
• White Meadowsweet was planted instead of American Elderberry.
2010 Construction Season
• White Meadowsweet and American Winterberry were planted instead of Speckled Alder.
See Section 3.7 for additional information regarding habitat reconstruction.
2.3.4 Oxbow Removal
2.3.4.1 Sediment Removal Method
According to Section 2.6 of the Design Report (ARCADIS 2009a), sediment removal was to be performed using a closed-bucket clamshell or a visor-equipped excavator bucket (with no drainage holes), unless productivity was negatively impacted such that USEPA’s on-scene coordinator (OSC) allowed the use of a standard clamshell or excavator bucket.
Prior to commencing removal activities, the OSC and ARCADIS inspected the sediment excavation area (the oxbow). Based on visual observations and limited probing, it was determined that due to the presences of tree limbs and branches, a closed-bucket clamshell or equivalent bucket head would not be appropriate for removal in the oxbow; therefore, a standard excavator bucket was used to remove material in the oxbow. See Section 3.4.4.7 for additional information.
2.3.4.2 Removal Footprint
Prior to commencing removal activities in the mouth of the oxbow in August 2010, ARCADIS and the USEPA OSC probed the soft sediment located in the mouth of the oxbow. Through this probing activity, it was determined that no soft sediment was present throughout much of the northern portion of the oxbow mouth. Because no soft sediment was observed, no excavation was required in this area. The planned removal footprint in the oxbow mouth was revised to incorporate only areas where soft sediment was present. See Section 3.4.4.7 for additional information.
3. Removal Activities
This section describes the actions performed to complete removal activities at the Plainwell No. 2 Dam Area. Removal activities were implemented between August 2009 and October 2010, and included pre-construction activities; installation of resuspended sediment control structures; soil/sediment removal; material dewatering, processing, and water treatment; transportation and disposal of excavated material; bank stabilization and habitat reconstruction; and project area restoration and demobilization. Daily activity reports are included in Appendix A and a photographic log is included in Appendix B.
3.2 Pre-Construction Activities
Pre-construction activities, such as endangered species survey; permitting; obtaining property access; identifying aggregate sources; mobilization and project area preparation; access road and staging area construction; and installation of erosion controls were performed by ARCADIS and its subcontractors in preparation for the TCRA. These activities are described in the following sections.
3.2.1 Indiana Bat Survey
The Indiana bat (Myotis sodalis) is listed as an endangered species by USFWS. The bats hibernate in caves over the winter and then migrate to summer habitat in wooded areas where they usually roost under loose tree bark on dead or dying trees (USFWS 2009). Habitat that has the potential to accommodate the Indiana bat was identified in the project area. Therefore, a site survey was conducted on March 4, 2009 to identify trees in the project area where Indiana bats might roost. The survey, required by and conducted under USFWS oversight, was led by Dr. Allen Kurta, Professor of Biology at Eastern Michigan University in Ypsilanti, Michigan. Dr. Kurta identified 11 trees where the Indiana bat might roost, and those trees were removed on March 30, 2009, at the direction of USFWS.
According to USFWS, the Indiana bat typically roosts in the area between April 15 and September 15. By the time clearing and grubbing was scheduled to begin in August 2009, any bats in the area would have already roosted in the trees identified by Dr. Kurta - trees scheduled to be removed to facilitate TCRA activities. Therefore, these trees were removed prior to April 15 to prevent the Indiana bat from roosting in the trees and being displaced or harmed during clearing and grubbing activities. Bats attempting to roost in the area would seek trees outside the TCRA area to establish habitat.
3.2.2 Permitting
Consistent with the provisions of CERCLA Section 121(e) (1), no permits for removal activities were required because all removal activities were conducted onsite.
ARCADIS received a permit from MDNR to install buoys in the river (MDNR 2009) to mark construction areas. MDNR closed the river to recreational use during construction activities. See Section 3.2.2 for additional information. The water generated during soil and sediment dewatering was managed in accordance with Substantive Requirements Document (SRD) – No. MIU990028 (MDEQ 2009). See Section 3.5.2 for additional information.
3.2.3 Property Access
ARCADIS obtained property access from private property owners and MDNR to conduct construction activities on their properties.
3.2.4 Identification of Borrow Material
Sources of sand backfill, aggregate material, river run rock, concrete, and topsoil (collectively, borrow material) were identified prior to construction. Borrow material sources were contacted to verify that material was available in the required quantities.
Borrow material used in restoration or grading activities was sampled at a rate of one composite sample per 10,000 cubic yards (cy) prior to use. Composite samples consisted of nine subsamples collected from various areas of the offsite source material selected in the field and biased towards areas of staining, if present. Backfill samples were analyzed for Target Compound List (TCL) volatile organic compounds, TCL semivolatile organic compounds, TCL pesticide/PCBs, Resource Conservation & Recovery Act metals, and total petroleum hydrocarbons (diesel range organics and gasoline range organics). Topsoil sources were also analyzed for grain size, pH, and total organic content to verify that they would support vegetation. Results of the sampling are summarized in Table 1 and laboratory analytical data are included in Appendix C-1. Samples were collected in accordance with the project-specific Quality Assurance Project Plan (QAPP) (ARCADIS BBL 2007b).
Analytical results were compared to applicable Part 201 cleanup criteria and Part 213 risk- based screening levels provided in Operational Memorandum No. 1 (Table 2, Column #19, Direct Contact Criteria & RMSLs), issued by the Remediation and Redevelopment Division of MDEQ on December 10, 2004. Sampling results indicate that all material from the borrow sources were acceptable for use.
Aggregate material used to construct access roads was re-used from the former Plainwell Impoundment TCRA completed in June 2009 and summarized in the former Plainwell Impoundment TCRA Final Construction Completion Report (ARCADIS 2010a). Virgin aggregate material from offsite borrow sources was used to supplement the re-used aggregate material as necessary. See Section 3.2.5 for additional information.
3.2.5 Mobilization and Project Area Preparation
Clearing and grubbing of vegetation from wooded areas was performed to the extent required throughout the project to establish access roads, staging areas, project support areas, and excavation areas. Cleared vegetation was chipped and used for dust and erosion control, hauled to landfills for offsite disposal, salvaged for marketable timber, used for constructing roads, or staged for later use.
Project area preparation activities commenced in August 2009 and included mobilization and construction of equipment, materials, support facilities, and personnel necessary for completion of the project. Support facilities included two temporary trailers for the subcontractor, one temporary office trailer for USEPA, and one temporary office trailer for ARCADIS. Facilities also included worker sanitation areas, equipment maintenance and storage areas, break areas, and personal decontamination areas.
Security measures including chain link fence and locked access gates were installed at each active work area within the project area. Temporary high-visibility fencing was used in areas where work did not warrant permanent fencing or to distinguish areas such as exclusion zones. Notification and warning signs were also posted where appropriate to label work areas.
With the cooperation of MDNR, the river was closed to public access throughout the duration of the project. ARCADIS provided signage stating that the river was closed. These signs and standard regulatory buoys were deployed by ARCADIS both upstream and downstream of the project area and at major boat launches in the area. Public notices were issued through MDNR and ARCADIS public communications specialists.
The Plainwell No. 2 Dam Area Traffic Control Plan Allied Paper, Inc./Portage Creek/Kalamazoo River Superfund Site (Traffic Control Plan, ARCADIS 2009b) was issued in July 2009 to detail traffic routes, entrances to public roads, traffic control measures, safety procedures, communication, and manifesting procedures. A revised Traffic Control Plan (Rev. 1 was issued in March 2010 (ARCADIS 2010b) to address alternate truck routes to the landfills due to potential construction or road closures.
3.2.5.1 Access Road Construction
Access roads were constructed to provide access to work areas along the banks of the Kalamazoo River and material staging areas, and to connect staging areas to public roadways (Figure 2). Three access points located on private residential property were established to access work areas.
The roads were constructed of geotextile material underlying aggregate material. Material specifications for these materials are included in Appendix D. Aggregate material imported from an offsite borrow source or from the former Plainwell Impoundment TCRA was used at the Plainwell No. 2 Dam Area TCRA. Aggregate imported from the borrow source was sampled according to the parameters described in Section 3.2.4. Aggregate material re-used from the former Plainwell Impoundment TCRA had previously been sampled as described in Section 3.2.3 of the Former Plainwell Impoundment Time-Critical Removal Action Final Construction Completion Report (ARCADIS 2010a).
Access roads connecting the work areas to the staging areas were referred to as haul roads. Prior to leaving the project area, vehicles that used the haul roads were decontaminated by pressure washing or by a truck tire wash installed at each staging area. Water from the truck tire wash was collected and treated with the decant water. See Section 3.5.2 for additional information regarding water treatment.
Where appropriate, pre- and post-construction soil samples were collected from access roads constructed on private property. Pre- and post-construction soil sampling was not required on MDNRE property. Air was monitored for particulate matter as activities required (such as truck traffic, pug mill operations) and based on the discretion of the health and safety officer. Air monitoring logs are included in the daily activity reports in Appendix A
The pre- and post-construction soil samples were collected to document the PCB concentration of subsurface soil before and after the TCRA. Samples were collected from 0 to 6 inches below the surface using a stainless steel trowel and submitted to KAR Laboratories in Kalamazoo, Michigan or Test America Laboratories (TAL) in Burlington, Vermont for PCB analysis. Access roads were sampled at a rate of one sample every 200 feet. Pre- and post-construction sampling results are included in Table 2. Laboratory analytical data are included in Appendix C- 2. Samples were collected and analyzed in accordance with the project-specific QAPP (ARCADIS BBL 2007b).
3.2.5.2 Staging Area Construction
Three staging areas were constructed for sediment and soil dewatering, processing, and staging before transport for offsite disposal. The staging areas were also used to collect and treat decant water from gravity drainage of the excavated sediments and soils. The staging areas, identified as Staging Areas 1, 2, and 3, varied in size (Figure 2). Staging area construction included grading and constructing berms from the underlying material to facilitate the collection of decant water for water treatment, installation of geosynthetic liner material, installation of aggregate material, set-up of material processing facilities, and installation of the water treatment system (Staging Areas 1 and 3 only). Dewatering water collected at Staging Area 2 was transported to Staging Area 1 for treatment. Trailers were only located at Staging Areas 1 and 3. See Section 3.5.2 for additional information regarding water treatment.
The size, location, and layout of the staging areas described in the Design Report (ARCADIS 2009a) were modified as necessary based on field conditions. Locations and orientations were modified at the request of the land owner whose property was utilized for staging area construction. Size was modified based on the estimated quantity of material to be processed in the area, and the layout of the staging area was modified to maximize the material processing area. See Figure 3 for a typical as-built layout of the staging areas. Table 3 summarizes the size and operating dates of the three staging areas.
Table 3 -- Staging Area Size and Operating Dates
Staging Area Approximate
Area (square feet)
1 122,000 May 2010 October 2010
2 45,000 May 2010 October 2010
3 90,000 August 2009 December 2009
The staging areas were cleared of vegetation and graded to collect water at one end. A sand base was installed at Staging Areas 1 and 3 to grade the construction area to a flat surface and berms were constructed around the sides of all staging areas to control water runoff. A sand base was not required to evenly grade Staging Area 2. Three layers of geosynthetic material were installed on top of underlying sand material. The geosynthetic layers served as a barrier between excavated material and the ground surface, and consisted of 40-millimeter high- density polyethylene (HDPE) geomembrane liner installed between two layers of non-woven geotextile fabric. The geotextile fabric was used to provide support and to prevent damage to the geomembrane liner. The HDPE layer served to prevent rainwater and decant water from
dewatering activities from migrating into the subsurface soils. Material specifications for these materials are included in Appendix D. The HDPE was seamed and tested to verify proper installation. Seaming records can be found in Appendix E. Aggregate material was installed above the second layer of geotextile fabric to serve as a base for work activities.
Depending on the intended use of the area, two types of aggregate material were placed above the geotextile material. 21AA aggregate was installed in areas used by off-road trucks and gravel-train trucks. Both natural and crushed concrete types of aggregate material were used. 6A rounded stone aggregate was used in sediment and soil decanting, processing, and staging areas. The material was sampled prior to use according to the sampling procedures outlined in Section 3.2.4. Results of the sampling are summarized in Table 1 and laboratory analytical data are included in Appendix C-1. A water truck was used in the staging areas for dust control as conditions warranted. Air was monitored for particulate matter as needed near the staging areas. Air monitoring logs are included in the daily activity reports in Appendix A.
As described in Section 3.2.5.1 for access road construction, pre- and post-construction samples were collected from the staging areas. A five-part composite sample, composited from the four corners and center of the staging area, was collected from each staging area. Samples were analyzed as described in Section 3.2.5.1.
Pre- and post-construction sampling results are included in Table 2. Laboratory analytical data are included in Appendix C-2.
3.2.5.3 Installation of Erosion Controls
Temporary erosion and sediment controls were installed before construction activities were initiated and were maintained through the duration of the project. Location-specific erosion and sediment controls were implemented at each removal area consistent with the measures described in the Design Report (ARCADIS 2009a). The specific locations of erosion and sediment controls were selected based on project area-specific considerations related to drainage, topography, and work activities. The selection of erosion and sediment control measures was based on, but not limited to, the scope of removal activities, location and topography, type of ground cover, type of material excavated, anticipated run-off from the project area, and operational/maintenance considerations.
Silt fencing consisting of a non-woven, needle-punched, polyester or polypropylene silt fence was used as the primary means of erosion control around all surface soil disturbances and potential run-off areas. Material specifications for the silt fence were reviewed and approved by ARCADIS prior to use (Appendix D).
Additional erosion control measures included spreading wood chips generated during clearing and grubbing activities throughout the area to reduce wind erosion.
During active work periods throughout the duration of the project, temporary erosion and sediment controls were inspected by the CQA Observer, documented in the daily reports, and maintained and/or modified on a daily basis, consistent with the recommended frequencies outlined in the Guidebook of Best Management Practices for Michigan Watersheds (MDEQ 1998). Temporary erosion and sediment controls were maintained, as appropriate, until a final surface cover was established as part of restoration activities.
3.3 Resuspended Sediment Control Structures
Control systems were installed in the river to minimize downstream transport of resuspended materials associated with the removal of sediments and soils. The selected systems had a relatively short setup/breakdown time and could be easily modified to adapt to changes in field conditions. The structures used to control resuspended sediment were capable of functioning under a variety of potential river flow and depth scenarios. The system used throughout the TCRA included a combination of turbidity curtains with a flow deflector wall.
Inspections of the sediment resuspension control systems were conducted each day at the beginning of removal activities, in response to visible sediment plumes migrating from the project area, or in response to turbidity levels measured above the action level. Routine daily resuspended sediment control system inspections consisted of a surface assessment of the condition, location, and anchoring of curtains and flow deflector walls. Inspections in response to turbidity levels above the action level metric began with a surface inspection using a boat. Additional inspections were conducted, as appropriate, following higher-flow periods, noticeable turbidity increases outside the system, unexpected system position/behavior, contact with the system by equipment or debris, or other abnormal events. Due to changing water levels and flow velocities, turbidity curtains were adjusted on a regular basis throughout the course of the project. Visible silt plumes were observed on several occasions, but did not result in elevated turbidity readings. Upon observation of a visible silt plume, excavation activities were suspended, and resuspended sediment controls were inspected and repaired.
3.3.1 Turbidity Curtains
Turbidity curtains were used extensively throughout the TCRA to control resuspended sediments. Curtains consisted of 22-ounce impermeable fabric, 8-inch diameter closed cell foam floatation devices, and double continuous 1/4-inch (upper) and 3/8-inch (lower) chain ballast enclosed in fabric pockets at the bottom edge of the curtain. The curtains had dual center tension cables that were reefable for water depth variation adjustments. A material
specification is included in Appendix D. One hundred-foot curtain segments were joined by metal side connecters and laced grommet edges to create a continuous barrier the length of an entire removal area (Figures 4.1 through 4.7). The curtains were anchored upstream to downstream using primarily steel sheeting driven to the river bed. Steel sheeting was generally used to connect adjacent 100-foot sections of turbidity curtain. Some galvanized steel fence posts were used in areas of low flow. The downstream and upstream ends of the curtains were attached to the shore. Throughout the project, the curtains were installed or removed as necessary.
Some damage to turbidity curtains occurred during excavation activities as a result of normal wear and tear. Damage was discovered by visual inspection of the curtains, identification of a silt plume escaping the curtain, and/or a turbidity exceedance. Curtains were repaired as soon as possible after damage was identified. Curtains that could not be repaired were replaced and staged for offsite disposal. At the conclusion of the project, curtains that were in good condition and could be re-used in the future were decontaminated, folded, and placed in storage.
3.3.2 Flow Deflector Walls
Flow deflector walls were used in conjunction with turbidity curtains to control resuspended sediments in areas where increased water depths or flow velocities were encountered. The use of flow deflector walls reduced the frontal impact of currents on the silt curtain system. The sheet pile used to construct the flow deflector walls was installed by machinery located on shore and was not affected by high flow velocities.
3.3.3 Resuspended Sediment Monitoring
Turbidity monitoring and surface water sampling were conducted throughout construction activities to monitor the effectiveness of the resuspended sediment control structures. Methods and results are described below.
3.3.3.1 Turbidity Monitoring
Real-time turbidity data were collected daily during removal activities using NexSens iSIC (Intelligent Sensor Interface & Control) automated meters from one fixed location upstream (approximately 200 feet) and from two fixed locations downstream (approximately 200 and 300 feet) of an active work area. A copy of the specification for the iSIC meter is included in Appendix D. Turbidity readings were collected from approximately mid-depth at all locations. The specific monitoring locations were adapted based on field conditions and river flow path. The USEPA OSC was typically consulted when selecting monitoring locations. The assessments were relative: downstream data were compared to concurrent upstream data to
identify increases in turbidity. Turbidity monitoring devices with associated telemetry equipment were installed at the locations upstream and downstream of the removal area. Four readings were collected each hour and processed to generate a moving average. That hourly average was compared to the standard.
A handheld YSI 650 MDS multi-parameter probe was present onsite in the event one of the automatic meters was to fail. In this event, workers could collect turbidity readings from the monitoring location every hour until the automatic meter was repaired. The turbidity meter was calibrated, operated, and maintained according to the manufacturer’s instructions and was able to measure turbidity at a resolution of +/- 1 nephelometric turbidity unit.
Turbidity readings were collected from all monitoring locations at the following times:
• Prior to placement of any equipment or materials in a work area.
• Following placement of equipment and materials but prior to removal actions.
• Every hour during removal actions.
• At the beginning of each work day and 2 hours after work was initiated in a given work area.
• At the end of each work day after activities were completed in a given work area.
The measurements collected at the location 200 feet downstream of the work area were used as an early warning of potential exceedances. The measurement collected at the location 300 feet downstream of the work area was compared against the upstream data. If the most downstream (usually approximately 300 feet) turbidity data were two times (2x) the concurrent upstream data, specific steps were initiated until the exceedance was mitigated to below the action level. Due to the proximity to the right diversion structure, turbidity monitoring locations could not be established 300 feet downstream of Removal Area 5A. Turbidity monitoring locations were installed as far downstream as possible (150 to 200 feet) without compromising worker safety by encroaching upon the right diversion structure.
Turbidity monitoring records are included in Appendix F. In the event turbidity reached unacceptable levels (i.e., downstream turbidity data were 2x the concurrent upstream data), a range of mitigation measures was implemented based on the magnitude of the turbidity changes noted.
An inspection of turbidity monitoring devices and resuspension controls was performed if an elevated turbidity reading was recorded at the 200 feet downstream location. However, no formal mitigation measures were performed unless the reading at the furthest downstream monitoring location exceeded 2x the concurrent upstream data.
Mitigation measures included inspecting resuspended sediment control systems for visible plumes, inspecting the turbidity meter to verify proper function, and slowing or halting excavation activities until turbidity levels returned to acceptable levels. During high river flow events, crews inspected the turbidity curtains twice daily and adjusted the turbidity curtains as needed.
3.3.3.2 Surface Water Samples
Surface water grab samples were collected for PCB analysis near the turbidity monitoring locations upstream and downstream of the active removal area on a weekly basis to observe spatial and temporal trends in PCB concentrations and were not used as a metric to control the rate of excavation. One grab sample each was collected from the furthest downstream location (approximately 300 feet downstream) and the upstream location (Figures 4.1 through 4.7). Samples were collected from mid-depth of the river channel using a Kemmerer™ stainless steel bomb sampler at approximately the same time for each weekly sampling event (2 hours after the start of excavation activities). Water quality parameters (temperature, conductivity, and turbidity) were recorded using an YSI 650R multi-parameter probe before collecting the sample.
Sampling procedures, preservation and handling, and analytical protocols for monitoring of PCBs were consistent with USEPA Method 608, with a quantification level of 0.1 microgram per liter (μg/L) (in accordance with the project-specific QAPP [ARCADIS BBL 2007b]). Samples were analyzed by TAL. A rinse blank was collected from the bomb sampler during each sampling event. A duplicate sample and matrix spike/ matrix spike duplicate samples were collected for one out of every 20 samples.
Surface water samples were only collected during excavation activities (September through October 2009 and June through September 2010). A total of 76 surface water samples (38 upstream/downstream pairs), 5 duplicate samples, and 38 rinse blank samples were collected.
Surface water sample results are summarized in Table 4 and laboratory analytical reports are included in Appendix C-4.
PCBs were detected in one sample (TS30143). Sample TS30143 was collected on October 15, 2009 from the turbidity monitoring location located 300 feet downstream of Removal Area 3. PCBs were not detected in any of the rinse blank samples. The PCB detection was an estimated concentration, as noted by the ‘J’ qualifier. This qualifier means that PCBs were positively identified at a concentration above the method detection limit, but below the quantification limit.
3.4 Soil and Sediment Removal
Areas to be removed as a part of the TCRA were delineated in the Design Report (ARCADIS 2009a) based upon a review of analytical studies performed on sediments, bank soils, and floodplain soils.
Background
As described in Section 1.2 of the Design Report, the Plainwell No. 2 Dam Area has been the focus of a series of investigations by ARCADIS, MDNR (now MDNRE), and USEPA since 2000. The most recent PCB data were generated during a sampling effort conducted by ARCADIS between 2008 and 2009. A variety of targeted studies of the impoundment were also conducted in 2009 to further characterize site topography, bank stability/disposition, flow hydrodynamics, equipment accessibility, and habitat quality. The results of these investigations were used to define the horizontal and vertical extents of soil excavation. The results of the delineation process are summarized in Section 1.4 and Drawings SR-1.1 through SR-1.7 of the Design Report (ARCADIS 2009a). Soil excavation was performed to these extents and confirmed complete per the requirements of the Design Report (ARCADIS 2009a).
Excavation Technique
Excavation was performed from the top-of-bank using an open bucket excavator equipped with a real time kinematic global positioning system (RTK GPS).
Excavated soil and sediment was loaded into off-road trucks and hauled to the nearest staging area for temporary storage, processing and/or reloaded for offsite disposal. Dry material was loaded directly into gravel-train trucks for transport to the offsite disposal facility. See Sections 3.5 and 3.6 for additional information regarding soil and sediment processing and disposal.
Soil and sediment removal areas were divided into three general categories:
1. Oxbow Sediments
2. Bank Soils
3. Islands
Sediment and soil removal areas were divided into six general removal areas, numbered 1 through 6, with Removal Area 1 being the most upstream removal area and Removal Area 6 being the most downstream removal area. Removal areas were further subdivided to facilitate efficiencies during excavation work. The letter “A” indicates the portion of the removal area
located along the northern bank of the river (e.g., 3A), while the letter “B” indicates the portion of the removal area located along the southern bank of the river (e.g., 3B). Not all six removal areas included portions on both sides of the river. If only one bank was removed, an ‘A’ or ‘B’ notation was not included (e.g., Removal Area 6).
Removal activities on the north side of the river were performed in 2009 and removal activities on the south side of the river were performed in 2010. Soil removal work generally progressed from upstream to downstream, beginning with Removal Area 1 on the north side of the river during the 2009 construction season. Soil and sediment removal work on the south side of the river began with Island 2, and then generally progressed from Removal Area 3B to Removal Area 6. The river stationing increased downstream to upstream, with Station 15+00 located at the downstream end of Removal Area 6. Stationing is presented in hundreds of feet upstream of the dam.
Oxbow sediment areas and islands were delineated independently from bank removal areas. Removal Areas 1 through 6 contained bank soils. Removal activities in these areas are discussed in the following sections.
Sediment and soil removal activities were performed over two construction seasons; from August 2009 through September 2010. 2009 removal activities were performed from September through October 2009; 2010 removal activities were performed from June through September 2010. Mobilization and demobilization activities occurred in the intermittent months.
At the completion of construction, approximately 15,700 cy of material had been removed and disposed at commercial offsite landfills.
3.4.1 Excavation Confirmation
Confirmation monitoring was performed to verify that the design specifications had been achieved and varied according to the work area being monitoring. Confirmation monitoring was conducted as soon as practical following completion of excavation so that additional response actions, if necessary, could be taken quickly, while the equipment was nearby. An RTK GPS- equipped excavator was used to give preliminary confirmation that excavation was completed in an area. Confirmation sampling was performed in all removal areas to verify completeness of excavation.
3.4.1.1 Surface Elevation Confirmation
Excavation of soil was initially confirmed by documenting the final surface elevation and comparing it to the neat line established in the Design Report (ARCADIS 2009a). Surface
elevation measurements were monitored as described below using a RTK GPS-equipped excavator.
Excavation of sediment was performed by recording a pre-construction surface elevation with the RTK GPS and excavating to the required depth as established in the Design Report (ARCADIS 2009a). The final post-excavation surface elevation was compared to the pre- construction surface elevation. See Section 3.4.2.1 for additional information on excavation.
The position of the excavator bucket as it removed sediments was displayed using a RTK GPS as manufactured by Topcon (Model 3DXi). A RTK GPS system was mounted on the excavator used during the project and communicated with a surveyed base station installed in an open area away from the river. The location of the base station changed as work progressed through the removal areas.
Three position sensors were mounted on the cab, boom, and bucket of the excavator. The three sensors worked together to triangulate the position of the bucket. The signals from these sensors were relayed to the base station which calculated errors from cover, rainfall, atmosphere, and other factors to improve accuracy.
3.4.1.1.1 RTK GPS Calibration
Prior to use of the RTK GPS unit, an initial calibration was completed by the manufacturer’s authorized representative. The initial calibration included equipment measurements and installation of the tilt sensors. During removal activities, vertical and horizontal checks were performed twice daily – once prior to commencing excavation activities and once during the day. Vertical and horizontal checks were completed by placing the excavator bucket on a pre- surveyed check-point located at a stationary point in the project area.
Additional calibrations were completed by a manufacturer’s authorized representative if one of the following occurred:
• Within 2 months after initial calibration and at least 2 months after each follow-up calibration.
• Upon equipment change or modification which affects the tilt sensor placements, including changes to the excavator bucket.
• When the vertical and horizontal twice daily checks were not within the specified manufacturer’s vertical tolerance limits of + 0.2 feet.
RTK GPS calibration logs are included in Appendix G.
3.4.1.1.2 RTK GPS Data Collection
The vertical and lateral extents of excavation are defined in Contract Drawings SR1.1 to SR1.7 in the Design Report (ARCADIS 2009a). Cross-sections of the excavation plan were converted to a three dimensional surface known as a triangular irregular network (TIN) that was viewed in real-time by the excavator operator.
The display mounted within the cab of the excavator showed the TIN as a plot of the maximum depth of penetration of the bucket versus the design neat line. Excavation proceeded until the neat line was reached.
Although bucket elevation data were displayed in real time, the data were not collected. Confirmation sampling was performed to verify that excavation was complete.
3.4.1.2 Confirmation Sampling
Completion of excavation to the extent defined in the Design Report (ARCADIS 2009a) was confirmed through PCB soil confirmation sampling for all excavation areas. The purpose of the confirmation sampling was to verify that no unacceptable PCB concentrations were left behind within the excavation boundaries. Therefore, confirmation sampling affected the depth of excavation but did not affect the lateral extent of removal which was determined using historical data before completion of the Design Report (ARCADIS 2009a). The PCB sampling performance standard was generally 5 milligrams per kilogram (mg/kg). The PCB confirmation sampling performance standard in the oxbow was 1 mg/kg. Confirmation sample locations for each removal area (as appropriate) were surveyed to document sample locations.
3.4.2 Removal Areas
The definition of each removal area and the excavation confirmation protocol performed varied for the three general categories of soil and sediment removed. The oxbow was excavated and sampled according to different methodology than the island and bank soil areas.
3.4.2.1 Oxbow
The oxbow area is located between Removal Areas 5B and 6. Material removed in the oxbow area included sediment in the mouth and channel of the oxbow. Due to limited pre-construction survey data, a neat line was not used to control the vertical extent of excavation in the oxbow. Instead, the sediment surface in the oxbow was surveyed immediately prior to excavation activities. The surface was then excavated from the surveyed pre-construction sediment elevation to the cut depth established in the Design Report (ARCADIS 2009a). Post-excavation sediment surface elevation was collected to confirm that excavation was complete. Excavation
was initially considered complete when the removal was performed to the prescribed excavation depth based on the maximum depth of penetration of the bucket as measured by the RTK GPS.
Confirmation sampling grids were generally established in the oxbow area in 50-foot lengths that spanned the width of the sediment removal area. At the mouth of the oxbow, the confirmation sampling grids were adjusted to be approximately 50 feet long and 50 feet wide (2,500 square feet [sf]). Due to the uneven dimensions of the oxbow, some confirmation sampling grids were modified to different configurations. The areas of these units did not exceed 2,500 sf.
Each confirmation grid was divided into six equal-sized cells (approximately 25 feet by 17 feet). Each of the six cells was divided into nine equally sized sub-sample locations. These locations were assigned a unique number from 1 to 9. A random number generator was used to generate a numerical value between 1 and 9 for each of the six cells, and the sub-sample was collected from the corresponding numerical location. Sediment samples were collected with a hand- driven push core from a depth of approximately 6 inches below the sediment surface. Soft sediment depth data were also collected by pushing a core to refusal while collecting samples or by using a rod to measure thickness. Water overlying the sediment in the core was decanted from the core sample prior to compositing the six sub-samples for submittal to the laboratory for PCB analysis. If the laboratory data confirmed that the PCB concentration for the composite sample was less than or equal to 1.0 mg/kg, the excavation of the unit was considered complete and no additional excavation was required. If the PCB concentration was greater than or equal to 1.0 mg/kg, an additional 6 inches was removed from the entire confirmation unit.
After additional excavation of sediments, sub-samples were collected from a random location within each of the six cells, composited, and submitted for laboratory PCB analysis. If the PCB concentration from the second round of sampling was less than or equal to 5.0 mg/kg, no further excavation of the area was required. However, if the PCB concentration remained greater than 5.0 mg/kg, an additional 6 inches was removed and the sampling process and analysis repeated at the direction of the USEPA OSC.
In some oxbow confirmation sampling grids, all soft sediment was removed down to the native riverbed. This generally occurred when excavation to the TIN was within 6 inches of the riverbed and excavating additional material was more time and cost effective than sampling the area and waiting for analytical data. The native riverbed consisted of sand and cobbles and could not be sampled. In these areas, the USEPA OSC and ARCADIS probed the area to determine if all soft sediment had been removed. If the USEPA OSC confirmed that all soft sediment had been removed and the area could not be sampled, excavation in the area was considered complete. Any soft sediment observed during probing was removed until the
USEPA OSC confirmed excavation to be complete in the area. See Section 3.4.4.7 for additional information regarding where sediment was excavated to native riverbed.
3.4.2.2 Bank Soil Removal Areas
Bank soil removal areas included soil materials located on the face of the bank between the toe- of-slope and top-of-bank, and soil materials located within a distance 30 feet landward from the median water line. A floodplain area adjacent to Removal Area 5B was included in the TCRA due to PCB concentrations identified during investigation activities. A neat line was established to delineate the lateral and vertical extent of excavation. The lateral and vertical extent of excavation was based on PCB sampling data as defined in Section 2.1 of the Design Report (ARCADIS 2009a).
Bank soils were removed and river banks were excavated at slopes no steeper than 3H:1V (horizontal: vertical) to reduce the potential for future erosion and sloughing, and to improve conditions for restored habitat features. Approximately 10,000 linear feet of river bank was addressed as part of the TCRA. The depth of soil removal in each targeted area varied and is depicted on Figures 5.1 through 5.17.
For the bank and floodplain soil removal areas, a nominal 75-foot long by 30-foot wide confirmation grid divided into six 25-foot by 15-foot cells was established. As soon as practical following excavation of a bank or floodplain soil confirmation grid, a sub-sample was collected from a random location within each of the six cells. Each of the six cells was divided into nine equally sized sub-sample locations. These locations were assigned a unique number from 1 to 9. A random number generator was used to generate a numerical value between 1 and 9 for each of the six cells, and the sub-sample was collected from the corresponding numerical location. Samples did not include sediment from the toe-of-bank. The sub-sample location could be modified in the field (at the direction of the USEPA OSC) if the majority of the surface area of a cell contained materials that appeared to be the materials targeted for removal. Soil samples were collected from the 6-inch depth increment below the floor of the excavation, composited, and submitted to the laboratory for PCB analysis. If the laboratory data confirmed that the PCB concentration for the composite sample was less than or equal to 5.0 mg/kg, the excavation of the confirmation grid was considered complete and no additional excavation was required. If the PCB concentration was greater than 5.0 mg/kg, an additional 6 inches was removed from the entire confirmation grid. Soil samples were again collected from a random location within each of the six cells, composited, and submitted for laboratory PCB analysis. If the PCB concentration from the second round of sampling was less than or equal to 5.0 mg/kg, no further excavation of the area was required. However, if the PCB concentration remained greater than 5.0 mg/kg, the confirmation grid was backfilled and restored unless USEPA and Georgia-Pacific determined that additional excavation should be conducted.
At the request of USEPA, split samples were collected from each of the individual sub-samples at 5% of the confirmation units prior to the homogenization process. The split samples were stored in accordance with the procedures identified in the Multi-Area QAPP (ARCADIS BBL 2007b) for analysis at the conclusion of the removal action. The confirmation sampling grids where sub-samples were split were identified prior to the start of removal activities each construction season. The selection was designed to obtain a distribution of confirmation units for this sampling purpose over the entire project area. Split samples were collected from Removal Area 2 Grid 3, Removal Area 3A Grids 10 and 13, Removal Area 4A Grid 2, Island 2 Grids 8 and 21, Removal Area 4B Grid 7, and Removal Area 6 Grid 5. The split samples were analyzed and compared to the composite data within 60 days after the TCRA was completed for use in the future evaluation of removal and/or remedial projects. The results of the sampling are included in Table 11. Laboratory analytical reports are included in Appendix C-3.
3.4.2.3 Island Removal Areas
Soil materials from two islands (Islands 1 and 2) were also removed as part of the TCRA. Islands 1 and 2 were excavated to a neat line established based on pre-construction sampling data. Island areas were excavated to the neat line and confirmation samples were collected according to the bank soil sample protocol described in Section 3.4.2.2.
3.4.2.4 Confirmation Sampling Surveying and Analytical Data
Sample locations were surveyed using the State Plane, North American Datum 1983 (NAD 83), Michigan South Zone for horizontal datum and National Geodetic Vertical Datum 29 for vertical datum. All analytical laboratory sampling and analysis were conducted in accordance with the project-specific QAPP (ARCADIS BBL 2007b). Soil samples were analyzed by KAR Labs and TAL for PCBs. The results of soil sampling are included on Figures 6.1 through 6.11 and Table 5. Laboratory analytical reports are included in Appendix C-3.
3.4.3 2009 Removal Activities
2009 removal activities included soil removal at Removal Area 1, 2, 3A, 4A, and 5A. Approximately 4,450 cy of material was disposed of at offsite commercial landfills. Excavation occurred upstream to downstream. The following sections summarize removal activities in each area. Bank stabilization activities and habitat reconstruction are discussed in Section 3.7.
3.4.3.1 Clearing and Grubbing
Vegetation was cleared from Removal Areas 1 through 5A in August and September 2009 to provide access for construction activities.
3.4.3.2 Removal Area 1
A flow deflector wall was installed at the upstream portion of Removal Area 1. Turbidity curtains were installed around Grids 1 through 8 and then Grids 9 through 12 in September 2009 to control resuspended sediments. Excavation of bank soil in Removal Area 1 was performed in September and October 2009. Excavated material was removed from this area and transported to Staging Area 3 for processing and disposal.
Approximately 1,050 cy of material from 840 linear feet of bank was excavated to the neat line from Removal Area 1. The removal area was divided into 12 confirmation sampling grids. Laboratory data confirmed that PCB concentrations in one grid (Grid 6) exceeded the PCB performance standard of 5 mg/kg. See Figure 6.11 and Table 5 for confirmation sampling grid locations and results. Laboratory analytical data are included in Appendix C-3.
The PCB concentration detected in sample TS20279 (6.9 mg/kg), collected from Removal Area 1, Grid 6 on September 24, 2009, exceeded the performance standard of 5 mg/kg. An additional 6 inches of material were removed on October 2, 2009 and the grid was resampled (TS20294). PCBs were not detected in sample TS20294 (0.33 mg/kg U2). Therefore, additional excavation was not warranted, and removal in the area was considered complete.
3.4.3.3 Removal Area 2
A flow deflector wall was installed at the upstream portion of Removal Area 2. Turbidity curtains were installed around Grids 1 th

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