Basis_of_Design_Report.pdf

BASIS OF DESIGN REPORT

LOWER ROUGE RIVER — OLD CHANNEL

Prepared for

U.S. Environmental Protection Agency’s Great Lakes National Program Office and

Honeywell International, Inc.

Prepared by

Anchor QEA, LLC1

9 Water Street, First Floor

Amesbury, Massachusetts 01913

EA Engineering, Science, and Technology, (MI) PLC2

5918 Meridian Blvd, Suite 4

Brighton, Michigan 48116

Amec Foster Wheeler Environment and Infrastructure

46850 Magellan Drive, Suite 190, Novi, Michigan 48377

January 2018 (Appendices A, B, M, and Q updated)

1 Anchor QEA, LLC, is the sole member of its affiliate, Anchor QEA of Michigan, LLC.

2 EA Engineering, Science, and Technology, Inc., does business as EA Science and Technology in the State of

Michigan and EA is affiliated with EA Engineering, Science, and Technology (MI), PLC.

Basis of Design Report January 2018 Lower Rouge River — Old Channel i 130287-03.01

TABLE OF CONTENTS

1 INTRODUCTION

1.1 Site Background

1.2 Project Coordination

1.3 Summary of Planned Remedial Action

2 REMEDIAL ACTION OBJECTIVES AND REMEDIAL ACTION LIMITS

2.1 RAOs Developed During the 2013 FS

2.2 Uncertainty Bounds of Numeric RAL Criteria

3 SUMMARY OF SITE INVESTIGATIONS

3.1 RI/FS Investigations

3.2 Pre-Design Investigation

3.2.1 Desktop Study

3.2.2 Sampling for Chemical Analysis

3.2.3 In-River and Upland Geotechnical Investigations

3.2.4 Shoreline Structural Survey

3.2.5 Bathymetric and Topographic Survey

3.2.6 Upwelling and River Velocity Surveys

3.2.7 Turbidity and Total Suspended Solids Surveys

3.2.8 Utility Mapping

4 DELINEATION OF REMEDIAL BOUNDARIES

4.1.1 Lateral Extents of Contamination

4.1.2 Vertical Extents of Contamination

5 EXISTING SITE CONDITIONS AND OTHER CONSIDERATIONS

5.1 Existing Site Conditions

5.1.1 River Navigation

5.1.2 Bridges and Structures

5.1.3 River Hydraulics

5.1.4 Utilities

5.2 Marine Traffic

6 REMEDIAL ACTION DELIVERY STRATEGY

Table of Contents

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7 BASIS OF DESIGN

7.1 Permanent Sheet Pile Wall

7.1.1 Limit Equilibrium Methodology

7.1.2 Representative Cross Sections

7.1.3 Model Development

7.1.4 Loading Cases

7.1.5 Factors of Safety

7.2 Site Support Facilities for Dredging, Capping, and Temporary Stabilization

7.2.1 Site Support Areas

7.2.1.1 Pointe Mouillee CDF

7.2.1.2 Honeywell Site Staging Area General Facilities

7.2.1.3 Material Storage

7.2.1.4 Decontamination Pad

7.2.1.5 Wastewater Treatment

7.2.1.6 Waterfront Support

7.2.2 Barge Selection

7.3 Sediment Dredging

7.3.1 Dredge Unit Development

7.3.1.1 Dredge-Only Areas

7.3.1.2 Dredge and Cap Areas

7.3.2 Dredge Design Assumptions

7.3.3 Dredge Equipment

7.3.4 Dredge Prism Slope Stability Evaluation

7.4 Dredged Material Handling, Transportation, and Disposal

7.4.1 Waste Streams

7.4.2 Strike Removal, Handling, and Disposal

7.4.2.1 Optional Upland Handling and Disposal

7.4.2.2 Landfill Disposal and Recycling

7.4.3 Navigation to CDF

7.4.4 Sediment Disposal

7.5 Slope Stabilization and Temporary Sheet Pile Wall

7.5.1 Slope Stability Modeling

7.5.2 Structural Stability Design

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7.5.3 Temporary Sheet Pile Wall Design

7.5.4 Dredging Techniques for Structural Stabilization

7.5.5 Special Instrumentation During Dredging

7.6 In Situ Capping

7.6.1 Chemical Isolation Layer

7.6.2 Filter Layer

7.6.3 Armor Layer

7.6.4 Cap Materials, Layer Thickness, and Overplacement Allowance

7.6.5 Placement Equipment and Techniques

8 HABITAT SUBSTRATE ENHANCEMENT

9 SITE RESTORATION

10 SUSTAINABILITY CONSIDERATIONS

11 ASSUMED CONSTRUCTION SEQUENCE AND SCHEDULE

12 ENVIRONMENTAL CONTROLS AND BEST MANAGEMENT PRACTICES

12.1 Best Management Practices

12.2 Engineering Controls

12.2.1 Mobile Resuspension System

12.2.2 NAPL Release and Sheen Control

12.3 AK Steel Water Intake Protection Barrier

12.3.1 Intake Protection Barrier Layout

12.3.1.1 Intake Protection Barrier Components

12.3.2 Intake Protection Barrier Anchoring

13 LONG-TERM MONITORING AND MAINTENANCE

14 PERMITTING REQUIREMENTS

15 ACCESS REQUIREMENTS AND EASEMENTS

16 CONSTRUCTION QUALITY ASSURANCE

16.1 Dredge Verification

16.1.1 Sampling Locations and Approach

16.1.2 Sequence of Response Activities

16.2 Dredged Material and Debris Disposal

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16.3 Cap, Residuals Cover, and Backfill Placement Verification

16.3.1 Verification of Import and Capping Material Quality

16.3.2 Cap, Residuals Cover, and Backfill Placement Verification

16.4 Water Quality Monitoring During Construction

16.4.1 Monitoring Location and Criteria

16.4.2 Monitoring Approaches

16.4.3 Response Actions and Limitations

16.5 Temporary Shoreline Stabilization

16.6 Permanent Shoreline Stabilization

16.7 Staging Area, Disposal, and Restoration Requirements

16.7.1 Staging Area

16.7.2 Water Discharge Monitoring

16.7.3 Restoration

17 CONSTRUCTABILITY AND VALUE ENGINEERING

18 ENGINEERING DRAWINGS AND TECHNICAL SPECIFICATIONS

19 ESTIMATE OF PROBABLE PROJECT COST

20 REFERENCES

List of Tables Table 2-1 Summary of Remedial Action Limits

Table 5-1 USACE Navigation Channel Project Depths

Table 5-2 Utility Summary

Table 7-1 Slot Dredging Requirements

Table 7-2 Cap A (DU-41) Thickness and Allowable Overplacement Requirements ...72

Table 7-3 Cap B (DUs-32 to -34) Thickness and Allowable Overplacement Requirements

Table 12-1 Turbidity Controls and Configurations

Table 12-2 East- and West-end Barrier Options

Table 14-1 LRROC Regulatory Requirements

Table 15-1 Parcels with Upland Disturbance

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Table 16-1 Construction Quality Assurance Monitoring Summary

Table 16-2 Water Quality Monitoring Approach per Construction Activity

List of Figures Figure 1-1 Property Ownership and Structures Map Figure 2-1 IWTU Prediction Error in Porewater Figure 5-1 LRROC Commercial Docks Figure 16-1 Dredge Verification Decision Matrix

List of Appendices Appendix A Engineering Drawings

Appendix B Technical Specifications

Appendix C Pre-Design Investigation Report

Appendix D Permanent Sheet Pile Wall Design

Appendix E Site Support Facilities Technical Memorandum

Appendix F Dredge Unit Development

Appendix G Dredge Design Slope Stability Evaluation

Appendix H Dredged Material Handling, Transportation, And Disposal Plan

Appendix I Shoreline Stabilization Technical Memorandum

Appendix J Cap Design

Appendix K Habitat Restoration Technical Memorandum

Appendix L Sustainability Memorandum

Appendix M Project Schedule

Appendix N Operation, Maintenance, and Monitoring Plan

Appendix O Environmental Permits

Appendix P Summary of USACE Value Engineering Screening

Appendix Q Estimate of Cost

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LIST OF ACRONYMS AND ABBREVIATIONS

ADCP Acoustic Doppler Current Profiling

Amec Foster Wheeler AMEC Foster Wheeler Environment and Infrastructure

AOC Area of Concern

BMP best management practice

BODR Basis of Design Report

BUI beneficial use impairment

CDF Confined Disposal Facility cfs cubic foot per second

CK0U consolidated undrained

CQA construction quality assurance

CSO combined sewer overflow

CWA Clean Water Act

CWALSHT Sheet Pile Wall Design/Analysis Program cy cubic yard

D50 median particle size

DOC depth of contamination

DPW Department of Public Works

DSS direct simple shear

DU Dredge Unit

EA EA Engineering, Science, and Technology, PLC

EOC elevation of contamination

FCV Final Chronic Value

ESBTU equilibrium-partitioning sediment benchmark toxicity unit

FS Feasibility Study

FOS factor of safety

GIS geographic information system

GLLA Great Lakes Legacy Act

List of Acronyms and Abbreviations

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GLNPO Great Lakes National Program Office

GLNPOCS Great Lakes National Program Office Cleanup Services

GLWA Great Lakes Water Authority

GPS global positioning system

H:V horizontal to vertical

HDPE high-density polyethylene

Honeywell Honeywell International, Inc.

IGLD85 International Great Lakes Datum of 1985

IPB Intake Protection Barrier

IWTU interstitial water toxicity unit

JPA joint permit application

LF linear foot

LRROC Lower Rouge River – Old Channel

MDEQ Michigan Department of Environmental Quality

MDNR Michigan Department of Natural Resources mg/kg milligram per kilogram

MGD million gallons of water per day

NAPL non-aqueous phase liquid

NAVD88 North American Vertical Datum of 1988

NOAA National Oceanic and Atmospheric Administration

NREPA Michigan’s Natural Resources and Environmental Protection Act

NTU Nephelometric Turbidity Unit

OMMP Operation, Maintenance, and Monitoring Plan

PAH polycyclic aromatic hydrocarbon

PDI Pre-Design Investigation

PE probability of exceedance

PGA peak ground acceleration

PRG preliminary remediation goal psf pounds per square foot

List of Acronyms and Abbreviations

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RAL remedial action limit

RAO remedial action objective

RD remedial design

RFTOP Request for Task Order Proposal

RI Remedial Investigation

RTK-DGPS real-time kinematic – differential global positioning system

Shoring Suite Shoring Suite Version 8.12n

SHPO State Historic Preservation Office

TOC total organic carbon

TSS total suspended solids

USACE U.S. Army Corps of Engineers

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

UU unconsolidated undrained

UVOST ultraviolet optical screening tool

VES vacuum extraction system

XPM Excavator Position Monitor

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1 INTRODUCTION

This Basis of Design Report (BODR) provides information to support the remediation of sediment containing polycyclic aromatic hydrocarbons (PAHs) and non-aqueous phase liquid (NAPL) in the Lower Rouge River – Old Channel (LRROC) located within a portion of the Rouge River Area of Concern (AOC). Project activities were conducted as part of the Great Lakes Legacy Act (GLLA) Project Agreement (USEPA and Honeywell 2013) for the LRROC between the U.S. Environmental Protection Agency’s (USEPA’s) Great Lakes National Program Office (GLNPO) and the non-federal sponsor, Honeywell International, Inc.

(Honeywell).

This BODR has been prepared through the collaborative efforts of Amec Foster Wheeler Environment and Infrastructure (Amec Foster Wheeler); Anchor QEA, LLC; EA Engineering, Science, and Technology, PLC (EA); and Ramboll Environ on behalf of the USEPA GLNPO and Honeywell.

1.1 Site Background

The LRROC is located in Detroit, Wayne County, Michigan, in a highly industrialized area along the northern and western boundaries of Zug Island (Figure 1-1). The LRROC is a 1.5-mile-long channel connecting the Detroit River with the Rouge River around Zug Island.

Flow in the LRROC is primarily governed by the conditions of the Detroit River, with surface water generally entering from the Detroit River at the northeast end of Zug Island, then flowing counterclockwise around Zug Island to the confluence with the main branch of the Rouge River. On rare occasions, flow reversals in the LRROC have been observed, as discussed in Section 5.1.3.

The LRROC is surrounded by industrial developments dating back to the late 1800s.

Discharge from industry, stormwater outfalls, combined sewer overflows (CSOs), and non-point pollution sources have contributed to the accumulation of contaminants within the sediments of the LRROC, but by far the predominant sources of contamination in the sediments were past industrial discharges. Contaminants within the sediments, primarily PAHs and NAPL, are contributing factors to the designated beneficial use impairments (BUIs) of the AOC, as summarized in the LRROC Feasibility Study (FS; AMEC et al. 2013).

Introduction

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The LRROC also contains a Federal navigation channel, and water depths are maintained by the U.S. Army Corps of Engineers (USACE). For most of the navigation channel, the dredge limits are 100 feet wide, with water depths of 17 to 25 feet relative to the low water datum of

571.1 feet International Great Lakes Datum of 1985 (IGLD85) (571.27 feet North American Vertical Datum of 1988 [NAVD88]). Due to relatively stable sediment conditions, the LRROC is dredged infrequently for channel maintenance. Areas of the navigation channel with water depths less than the authorized depth are typically limited to edges of the channel, leading to steep riverbank slopes.

1.2 Project Coordination

As part of the Rouge River AOC, the LRROC is a “target remediation site” under the GLLA.

In May 2010, USEPA GLNPO and Honeywell entered into a project agreement to conduct a Remedial Investigation (RI) and FS for the LRROC. Following completion of the RI (Weston 2012) and FS (AMEC et al. 2013), USEPA GLNPO and Honeywell entered into another project agreement in September 2013 to conduct the remedial design (RD). USEPA GLNPO and Honeywell worked collaboratively to design a plan to remediate contaminated sediments within the LRROC addressing BUIs with the goal of assisting the eventual delisting of the larger Rouge River AOC. The RD documented in this BODR was developed by a team of four firms: EA on behalf of USEPA GLNPO and Amec Foster Wheeler, Anchor QEA, and Ramboll Environ on behalf of Honeywell. Design tasks and responsibilities were divided among the members of this team and are documented in the RD project agreement (USEPA and Honeywell 2013). This BODR represents the collaborative work of all parties within the project team.

1.3 Summary of Planned Remedial Action

The LRROC remedy consists of a combination of dredging and engineered capping.

Sediment removal within the LRROC will consist of dredging approximately 70,000 cubic yards (cy) of sediment over an area of approximately 10 acres. The dredge footprint has been divided into 41 individual Dredge Units (DUs)3 (see Appendix A; Great Lakes National

3 DUs are numbered from 1 to 42 with no DU 39, which was eliminated during the design process.

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Program Office Cleanup Services [GLNPOCS] Engineering Drawings; Sheets C-300 to C- 305). Within each DU, the removal depth is specified as either an elevation or a depth below the existing mudline and further translated into final design grade lines as shown in the GLNPOCS Engineering Drawings in Appendix A (GLNPOCS Engineering Drawings; C-300 to C-305). Dredged material will be transported by barges and disposed of at the Pointe Mouillee Confined Disposal Facility (CDF).

Given the existing steep slides slopes of the LRROC, dredging without prior slope stabilization could result in destabilization of the slopes and shoreline structures. Therefore, as part of the remedial activities, temporary and permanent sheet pile walls will be installed to stabilize the marginal shorelines and upland structures prior to the start of dredging activities. A permanent sheet pile wall will be installed along the mainland bank of the LRROC (Appendix A; Permanent Sheet Pile Wall Engineering Drawings; Sheets 4, 19, 20 and 21) to allow for the complete removal of contaminated sediments. This permanent sheet pile wall will be anchored with tiebacks and deadmen.

Temporary sheet pile walls are planned for four locations along the LRROC dredge footprint to allow dredging to occur under stable conditions (see Appendix I for details). Backfill will be placed following sediment removal in these areas and then the sheet pile walls will subsequently be removed.

Following dredging activities, an engineered cap will be installed in DUs 32, 33, 34, and 41 (Appendix A) where complete removal of contaminated sediments is not practical or cost-effective. The engineered cap will physically and chemically isolate the remaining contaminated sediments from overlying surface water, ecological receptors, and humans.

The RD in these areas requires some dredging prior to cap placement to provide sufficient clearance, such that the top of cap elevation is at least 3 feet below the authorized navigation channel elevation. The 3 feet between the top of the cap and the authorized navigation channel will provide a buffer so that future maintenance dredging within the LRROC does not impact the placed caps (communication with Jon Imbrunone of the USACE Detroit District).

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A post-dredge verification program will be implemented to verify that target dredge elevations have been achieved, and to assess the sediment quality of the post-dredge surface.

If contamination in post-dredge residuals remains above acceptable levels for those areas not subject to capping or stabilization backfill (placed following dredging in areas of temporary sheet pile stabilization), additional response actions will be performed in accordance with the residuals management decision tree discussed in Section 16.1. Residuals management actions may include additional dredging and/or placing a layer of clean cover material or engineered cap.

In total, the remedial construction elements will include:

• Installation of 2,540 linear feet (LF) of permanent sheet pile wall (total length including windows), including tiebacks and deadmen (Sheet Pile Wall Stations4 100+00 to 125+40), with five windows for utility/bridge clearance to facilitate dredging

• Placement of approximately 8,000 cy of fill shoreward (e.g., upland) of the permanent sheet pile wall between the top of riverbank and sheet pile wall

• Installation and removal of approximately 700 LF of temporary sheet pile walls to facilitate dredging

• Removal of debris from within the planned dredge areas including an estimated 13 cars, 50 tires, and 8 pile clusters, 50 miscellaneous pilings, 2 dock structures, and other unknown debris

• Removal of approximately 70,000 cy of contaminated sediments (including overdredge allowance)

• Placement of approximately 0.7 acre (total) of sediment cap to be installed in two individual capping areas

• Placement of approximately 13,000 cy of stabilization backfill, where temporary and permanent sheet pile walls and slot dredging will be used

• Possible residuals dredging based on the results of verification sampling

4 Note that the Sheet Pile Wall Stations begin at 100+00 and are measured along the alignment of the wall.

Sheet Pile Wall Station 100+00 is at approximately River Station 8+85 and Sheet Pile Wall Station 125+40 is at approximately River Station 33+75. These station numbers are independent from the river stations. See Appendix A; Permanent Sheet Pile Wall Installation Engineering Drawings; Sheets 4, 19, 20 and 21 for Sheet Pile Wall Stationing.

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• Possible placement of post-dredge cover material based on the results of verification sampling

GLNPOCS Engineering Drawings and Technical Specifications are provided in Appendix A and Appendix B, respectively.

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2 REMEDIAL ACTION OBJECTIVES AND REMEDIAL ACTION LIMITS

Remedial action objectives (RAOs) were developed for the LRROC during the FS (AMEC et

al. 2013) as a means of contributing to the removal of the following BUIs:

• Loss of Fish and Wildlife Habitat

• Degradation of Benthos

• Restriction on Dredging

• Restrictions on Fish and Wildlife Consumption

• Fish Tumors or Other Deformities

2.1 RAOs Developed During the 2013 FS

RAO 1: Reduce the exposure of the aquatic benthic community to PAH concentrations in sediment that are greater than protective levels.

Achieving this RAO will help reduce potential toxicity associated with LRROC sediment PAH exposure to biota and will indirectly reduce the potential for fish tumors and deformities, to the extent they may occur due to exposure to LRROC sediments. This RAO addresses ecological exposures based on PAHs in sediment. To the extent that sediment contaminants contribute to Rouge River AOC BUIs, achieving this RAO will contribute to the improvements associated with the following BUIs:

• Loss of Fish and Wildlife Habitat

• Degradation of Benthos

• Restriction on Dredging

• Restrictions on Fish and Wildlife Consumption

• Fish Tumors or Other Deformities

RAO 2: Reduce human exposures for direct sediment contact to PAHs and NAPL in sediments of the LRROC.

This RAO addresses direct human contact with sediments impacted by PAHs and/or NAPL.

Direct human contact with impacted sediments can be reduced through sediment remedial actions and the use of access restrictions and institutional controls.

Remedial Action Objectives and Remedial Action Limits

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RAO 3: Improve habitat within the LRROC.

This RAO focuses on improving the aquatic habitat within the LRROC. Habitat improvements do not necessarily serve to achieve other RAOs but will benefit the ecology as a whole within the LRROC.

To meet the RAOs outlined above, the following preliminary remediation goals (PRGs) were developed during the FS and adopted as remedial action limits (RALs) during the RD phase (Table 2-1).

Table 2-1 Summary of Remedial Action Limits

Contaminant Media Depth Interval RAL

PAHs Surface sediment 0-1 foot IWTU1 = 5

PAHs Subsurface sediment Greater than 1 foot ESBTU2 = 7.5

NAPL

Surface and subsurface sediment All depths Presence of NAPL

Notes:

ESBTU = equilibrium-partitioning sediment benchmark toxicity unit IWTU = interstitial water toxicity unit NAPL = non-aqueous phase liquid (NAPL defined for the project as saturated layers, continuous oil-phase streaks, multiple blebs, or zones that have the potential to be mobile; the observation of tiny flecks, individual blebs, or sheens are not considered source material and would not be classified as “NAPL”) PAHs = polycyclic aromatic hydrocarbons RAL = remedial action limit 1 An “upper bound” IWTU of 13 was used in determining remediation boundaries when using a multiple-lines-of-evidence approach (see Section 2.2).

2 An “upper bound” ESBTU of 12 was used in determining remediation boundaries when using a multiple-lines-of-evidence approach (see Section 2.2).

Individual PAH compounds have a wide range of chemical properties that affect bioavailability and benthic toxicity. The RI/FS and RD used the PAH toxicity metrics of interstitial water toxicity units (IWTUs) and equilibrium-partitioning sediment benchmark toxicity units (ESBTUs) (USEPA 2003, 2009) to assess PAH contamination in the LRROC.

The interpretation of both of these metrics is based upon a target water concentration of each PAH compound, the Final Chronic Value (FCV). The USEPA (2003) derived the FCVs for PAHs using the National Water Quality Criteria Guidelines as the toxicity endpoint for the

Lower Rouge River — Old Channel 8 130287-03.01 equilibrium partitioning sediment benchmarks. USEPA indicated “this value is intended to be the concentration of a chemical in water that is protective of the presence of aquatic life.”

For both the IWTU and ESBTU, the toxicity units for each PAH compound (defined as the ratio of the measured or estimated concentration of the compound in porewater to the FCV) are summed to provide an estimated total toxicity for the whole sample. The IWTU is based on the analysis of PAHs in porewater and, thus, directly reflects PAH bioavailability; it provides the best estimate of benthic toxicity relevant to PAHs in sediment. The ESBTU is based on the partitioning of PAH compounds between the total organic carbon (TOC) in bulk sediment and the porewater; it is used to estimate the porewater concentration. In samples for which porewater data are available (these are limited to surface sediments), IWTU values are used; in all other samples, ESBTU values are used.

The RAL for PAH IWTU was identified from a sediment toxicity database that was generated by the Energy and Environmental Research Center between 2003 and 2011. The database was obtained from Arp et al. (2011). The RAL for porewater PAHs was identified as the IWTU level in the Arp et al. (2011) dataset associated with 80% survival of Hyalella (H.)

Azteca (IWTU=5). This target corresponds to the control performance criterion for H. azteca survival in laboratory toxicity tests (USEPA 2000) and is commonly used as an approximation of a biologically significant effect threshold (e.g., Phillips et al. 1998).

The ESBTU value corresponding to an IWTU of 5 was calculated using a site-specific dataset of paired sediment and porewater samples, collected from the LRROC in 2011. The relationship between IWTU and ESBTU was determined through linear regression of the natural log-transformed data (Appendix A of the FS; AMEC et al. 2013). The ESBTU value corresponding to an IWTU of 5 is approximately equal to 7.5, which was selected as the RAL for the subsurface sediment in the LRROC.

2.2 Uncertainty Bounds of Numeric RAL Criteria

Delineation of areas for remediation is a complex process that takes into account factors such as the local spatial distribution of chemical concentrations, outliers, geography, and geomorphology. The objective of this section is to determine upper bound values for ESBTU that can be used as a line of evidence in situations where delineation is uncertain.

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As noted in Section 2.1 and further described in the FS (AMEC et al. 2013), the numerical RALs selected for the project include an IWTU of 5 and an ESBTU of 7.5. The IWTU value of 5 is actually a conservative estimate of the value corresponding to 80% survival of H. Azteca in laboratory studies. This is because the IWTU corresponding to H. azteca survival of 80% is actually equal to 7, as shown in Figure A-1 in Appendix A of the FS (AMEC et. al. 2013). In the FS, the PRG for IWTU was decreased from 7 to 5 for the site in order to provide an additional “safety factor” with respect to protectiveness of the benthic community. During delineation, the conservative nature of the RAL is considered in the weight-of-evidence evaluation.

An additional investigation of the relationship between survival and IWTU was performed as part of the RD, with the goal of defining an IWTU range acceptable for use in remedial decision-making, in conjunction with other lines of evidence as discussed in Section 4. The approach is based upon the predictive power of a specific IWTU value. This was evaluated using the database upon which the PRGs were developed (Arp et al. 2011). The approach involved counting, in this published database, for various values of IWTU, the number of “false positives,” which are samples that had IWTU values higher than a specific value but were non-toxic to study organisms; and “false negatives,” which are samples that had IWTU values lower than a specific value but were toxic. In the context of this evaluation, primary interest was in false negatives, because these represent cases in which a toxic sample could be mistakenly classified as non-toxic (i.e., potentially “missing” significant contamination in the remediation).

The Arp et al. (2011) data produce a false negative of 5% at an IWTU of 13. That is, in the published database, of the samples with IWTU less than 13, only 5% were classified as toxic (see Figure 2-1). Based on this relatively low false negative rate, the RD team (Anchor QEA, Amec Foster Wheeler, EA, and Ramboll Environ) concluded that that an upper bound IWTU value of 13 should be used when using multiple lines of evidence in drawing final remediation limits, as discussed in Section 4. This upper bound was only used in evaluating outlier samples that were not supported by surrounding data.

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Similar to the RAL, an upper bound value for ESBTU was determined by regression using the selected IWTU value. Using the upper bound IWTU of 13 as discussed in the previous paragraph, the regression analysis produced the ESBTU value of approximately 12.5.

Therefore, the ESBTU value of 12 was selected as an upper bound value to be used in a multiple-lines-of-evidence determination of the lateral and vertical extent of contamination, as discussed in Section 4.

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3 SUMMARY OF SITE INVESTIGATIONS

Investigation of sediment, shorelines, and water quality in the LRROC has been ongoing for a decade. Data serving as the primary basis for design originated from three sources:

• RI Report for the LRROC site (Weston 2012)

• FS Report of the LRROC site (AMEC et al. 2013)

• Pre-Design Investigation (PDI) Report for the LRROC site (EA 2016)

3.1 RI/FS Investigations

Below is a brief summary of the field activities, studies, and investigations performed on the LRROC to support the RI/FS:

• Hydrographic/side-scan sonar and sub-bottom profile surveys to estimate sediment surface elevations, sediment thickness and volume, sediment texture, types of debris, and locations

• Geophysical surveys to identify utilities and sediment thickness within the LRROC

• Bulk sediment and porewater sampling and analyses to define the nature and extent, and bioavailability of PAH contamination

• Bulk sediment sampling for waste characterization

• Acoustic Doppler Current Profiling (ADCP) and the installation of sediment traps to support a sediment transport evaluation

• Borings along the riverbanks to assess the possible presence of NAPL using the ultraviolet optical screening tool (UVOST) technology in conjunction with visual observations

• Geotechnical borings and testing to support assessment of shoreline stability and the design of potential stabilization measures

• A habitat assessment and shoreline conditions/in-river structure survey using visual observations

3.2 Pre-Design Investigation

The PDI was a multi-phased effort conducted during the RD phase of the project performed between August 2014 and February 2016.

Summary of Site Investigations

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Additional analytical and geotechnical data were collected and were used in conjunction with data collected during the RI/FS investigations to support the RD. The following activities were performed, and data and samples were collected during the field investigation:

• A desktop study, at the outset of the PDI, to evaluate existing site information as a means of determining the suitability of the available information for use in the RD

• Chemical analysis to refine the vertical and horizontal extent of the target remedial footprint, and determine the volume of contaminated sediment

• In-river geotechnical investigations to refine the vertical and horizontal extent of the target remedial footprint, and to support the design for shoreline stabilization approaches associated with the channel side slopes, dredge prism geometry, and/or capping components

• Upland geotechnical investigations to support the design of shoreline stabilization measures associated with channel side slopes, permanent sheet pile system, dredge prism geometry, and/or capping components

• Shoreline structural survey of 5,000 LF of shoreline to locate and assess the baseline condition of in-water shoreline structures to support evaluations of structural integrity, develop alternatives for shoreline stabilization near structures, and evaluate potential impacts to existing structures due to dredging

• Bathymetric survey of the entire project area using multi- and single-beam hydrographic survey to determine water depths and riverbed elevation, evaluate changes in riverbed topography (deposition/erosion) since the 2010 survey, identify areas with moderate- to large-scale debris items at the sediment-water interface, and identify areas of sediment texture and/or composition change

• Topographic survey to determine the slope and elevation of the existing riverbanks, evaluate changes in the basin morphology through deposition or erosion since the 2010 survey, document the condition of existing infrastructure to determine suitability/stability during or following construction, and aid in identifying areas suitable for containment facility construction

• Groundwater upwelling survey to locate areas potentially subject to significant upwelling within the proposed capping areas of the LRROC

• Turbidity studies to assess typical conditions in the LRROC

• Utility surveys to verify the presence/absence of utility crossings within the dredge footprints

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A detailed summary of the PDI methods and results is presented in the PDI Report (Appendix C) and are described in more detail in the following subsections.

Additional geotechnical borings beyond those noted in the PDI Report were collected in February 2016 by Amec Foster Wheeler to supplement the upland geotechnical data collected as part of the PDI and support the design of the permanent sheet pile wall. A description of this supplemental geotechnical investigation and the results of the subsequent analyses is presented in Appendix D.

3.2.1 Desktop Study

As part of the initial PDI effort, existing site characterization information was compiled, such as data received from landowners and stakeholders, data received from State and Federal agencies from prior environmental surveys, data collected during the RI/FS, and publicly available information from State and local agencies. A detailed desktop study was performed as a means of determining the suitability of the available information for use in the RD. The evaluation was designed to identify obvious gaps in data coverage, suspect data, or necessary updates to available information. The desktop study indicated that debris, habitat, and water elevation data were sufficient for conceptual-level design and permitting needs, and that a shoreline structural survey, bathymetry and topography surveys, and underwater utility mapping were required. These studies are discussed further in the following subsections.

3.2.2 Sampling for Chemical Analysis

Sonic coring was performed in 2014 and 2015 as part of the PDI to collect sediment samples at 72 locations, with core depths ranging from 4 to 25 feet below sediment surface. Grab samples from the sediment surface were collected at 45 locations to provide extracted porewater for chemical analysis and IWTU calculations. Sampling locations were based on an analysis of vertical and horizontal data gaps performed by the design team. Within each core, sediment lithology was logged, observations of NAPL were recorded, and samples were collected from each 1-foot depth interval for potential analysis. The decision to analyze a sample was based on past sampling results and field observations. In some cases, the initial round of analysis was followed by analysis of archived samples to determine the horizontal

Lower Rouge River — Old Channel 14 130287-03.01 and vertical boundary of contamination. Analysis of archived samples was determined based on a weight-of-evidence approach by the project design team; this was typically triggered by detection of NAPL or ESBTU in depth intervals that were not vertically bounded downward.

The decision to analyze archives also considered whether additional vertical characterization would assist in setting dredge boundaries. Samples were analyzed for percent moisture, TOC, and 38 PAHs. PAH results were used to calculate ESBTU for sediment and IWTU for porewater. Sampling results—including observations of NAPL, ESBTU exceedance in sediments below 6 inches depth, and IWTU exceedance in porewater in the top 6 inches of sediment—were combined with similar data from past efforts and used in a weight-of-evidence approach to define vertical extent and horizontal extent, as described in Section 4.

Analytical results show a range of total PAH concentrations from 0.079 milligram per kilogram (mg/kg) to 39,420 mg/kg in sediment; this is based on the sum of all 38 PAHs analyzed. ESBTU measured in subsurface sediments (below 1-foot sediment depth) demonstrated values that ranged from 0.0352 to 568.3. ESBTU are elevated in the former Detroit Coke and Tar plants (ESBTU ranging from less than 1 to 569), near the AK Steel water intake plant (ESBTU ranging from less than 1 to 321), and in front of the Superior Materials Cement Plant (ESBTU ranging from less than 1 to 112). Elevated ESBTU were rarely measured deep within clay layers but were found on occasion within the top 1 to 2 feet of the lacustrine clay. IWTU measured for porewater in surface sediments ranged from 0.00191 to 94.2. Analytical porewater results showed elevated porewater values above RALs west of the former Detroit Coke and Tar plants (IWTU ranging from less than 1 to 536) and on either side of the Delray Connecting Swing Bridge (IWTU ranging from less than 1 to 1,860). Maps of ESBTU exceedances and core profiles showing exceedances of RALs can be found in Appendix C.

3.2.3 In-River and Upland Geotechnical Investigations

In-river and upland geotechnical data were collected to support the design for shoreline stabilization approaches associated with the channel side slopes, dredge prism geometry, and/or capping components. Hollow-stem auger drilling was used to collect split spoon and thin-walled steel tube samples from 14 in-river and 5 upland boring locations (does not include February 2016 borings; Appendix D). Lithology was logged, and samples were

Lower Rouge River — Old Channel 15 130287-03.01 collected for geotechnical and/or chemical analysis. Geotechnical testing included specific gravity, bulk density, percent moisture, Atterberg limits, consolidation, and multiple strength parameters. Sampling focused largely on clays and till but also included some samples in shallower layers.

Geotechnical investigations identified four primary strata extending downward from the surface. Within the river, there are shallow layers of soft sediment deposits, interbedded alluvial sand/silt/clay, lacustrine clay layer, and glacial till. These deposits are similar throughout the LRROC except in three locations where the depth to lacustrine clay is greater: 1) in front of the former Detroit Coke and Tar plants; 2) in front of the AK Steel water intake plant; and 3) near the Superior Materials Cement Plant. In the upland areas, the soft sediment layer is not present, and the surface is instead occupied by fill; underlying layers of alluvium and lacustrine clay are similar. Glacial till is the underlying stratum below all other layers, typically found at an average depth in the river of 57 feet below sediment surface and 85 feet below the upland surface. Till was encountered at an average elevation of 500 feet (NAVD88).

Geotechnical analyses identified a range of grain size, bulk density, and moisture content for soft sediments, alluvium, and lacustrine deposit. Moisture content values were generally low for a fine-grained deposit. The lacustrine clay tends to have an average low undrained shear strength of 400 pounds per square foot (psf) within the limits of the river and 600 psf upland based upon the results of unconsolidated undrained (UU) and consolidated undrained (CK0U) triaxial shear strength testing, vane shear testing, and direct simple shear (DSS) laboratory testing. Results of other tests and specific test results are documented in the PDI Report and in the geotechnical boring logs presented in Appendix C; additional geotechnical data from a supplemental geotechnical investigation by Amec Foster Wheeler is presented in Appendix D.

As discussed in Section 3.2, the results of supplemental upland geotechnical investigations by Amec Foster Wheeler to support the design of the permanent sheet pile wall are presented in Appendix D.

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3.2.4 Shoreline Structural Survey

A shoreline structural survey was performed in 2014 for 5,000 LF of shoreline to locate and assess the baseline condition of in-water shoreline structures to support evaluations of structural integrity, develop alternatives for shoreline stabilization near structures, and evaluate potential impacts to existing structures due to dredging. Eleven shoreline structures were selected for investigation based on the existing plans for the RD and preliminary observations of structures in the RI (Weston 2012). The investigation included an above-water, visual conditions survey as a baseline assessment.

The PDI Report includes a report detailing investigations of the 11 structures surveyed.

Overall findings in the structural survey area as follows:

• The visible portion of the pipe bridge foundations were in satisfactory condition.

• The Zug Island bulkhead, U.S. Steel outbuilding, Zug Island Road Bridge, Ford Water intake structure, and Detroit/Windsor Truck Ferry bulkhead were in fair condition.

• The Zug Island Ore Dock, abandoned bridge abutments, and Ferriss Marine shoreline structures were in fair to poor condition.

• The Honeywell shoreline structures and Superior Materials Cement Plant Wall were in poor condition.

Structure condition was considered as part of RD. The structural survey provided a baseline condition assessment above water consistent with structural engineering standards of practice. This included observations of state of structure deterioration, acoustic measurements of sheet pile thickness of bulkheads, and classification of structure component type and size for subsequent evaluations.

3.2.5 Bathymetric and Topographic Survey

A bathymetric survey of the entire project area was performed during the PDI using multi-and single-beam hydrographic survey methods to determine water depths and riverbed elevation, identify areas with moderate- to large-scale debris items at the sediment-water interface, and identify areas of sediment texture and/or composition change. A topographic survey was performed to determine the slope and elevation of the existing riverbanks above the water line. A vessel-mounted, high-frequency, beam-forming, multi-beam echosounder

Lower Rouge River — Old Channel 17 130287-03.01 system was interfaced with a high-resolution inertial navigation system to precisely measure water depth and geodetic position. The survey was completed with 200% coverage of the river bottom within navigable waters, and sufficient data in non-navigable water were collected for development of a seamless digital elevation model between in-water bathymetry and shoreline topography. In conjunction with the bathymetric survey, a topographic LiDAR survey was completed for shoreline areas and non-navigable waters. A terrestrial laser scanner was used to provide high-resolution views of waterfront structures, crossings, and riverbanks. Data were processed to account for water level, speed of sound cast data, and remove noise from multi-beam data.

Specific results of the bathymetric survey are available in the PDI Report. A graphic of site bathymetry is included in Appendix C. Bathymetry results indicate a large amount of debris is present underwater in the LRROC, including, but not limited to, 13 cars; tires, such as large size truck tires; one boat (located outside the dredge footprint); and at least four areas of general debris that may include large logs and/or construction debris. The general LRROC morphology is U-shaped with steep side slopes and a flatter, less sloping bottom. More than half of the side slopes of the LRROC are over-steepened (greater than a 2-foot horizontal to 1 foot vertical [2H:1V] slope) with portions of slopes being 1.5H:1V or steeper. Bathymetry indicates areas where in-water and shoreline structures are noteworthy, including seawalls, dock piles, and remnant dolphins. PDI bathymetry and topography data were used to compile base layers for the RD.

3.2.6 Upwelling and River Velocity Surveys

Upwelling and river velocity surveys were performed to identify areas that are potentially subject to significant (i.e., artesian) upwelling within the proposed capping areas of the LRROC, and measure river velocity to inform if additional design studies (quantitative measures of upwelling) were required. Upwelling surveys were conducted by measuring temperature, conductivity, pH, turbidity, salinity, dissolved oxygen, and oxidation-reduction potential throughout the water column at stations arranged in transects. Key findings of this survey include two locations where results indicated that upwelling potentially exists: 1) in the known upwelling area on the banks of Zug Island across from the former Detroit Tar Plant; and 2) south of the Zug Island Road Bridge within the main channel. Although the

Lower Rouge River — Old Channel 18 130287-03.01 two sampling locations south of the Zug Island Road Bridge have potential to be associated with upwelling, it is possible that results were influenced by a stormwater outfall immediately upstream of these locations. After further discussion and evaluation with the project team, it was noted that these locations may be indicative of low-level upwelling but are not indicative of significant artesian upwelling. The velocity study results indicated that flow was highest along the shoreline transect, followed by the AK Steel water intake plant, and lastly, the Superior Materials Cement Plant transect. Specific results of upwelling studies are available in the PDI Report

3.2.7 Turbidity and Total Suspended Solids Surveys

Turbidity and total suspended solids (TSS) may increase during dredging. To better understand ambient conditions, turbidity and TSS were monitored near the AK Steel water intake plant for 1.5 months in 2014 and 2015. Key findings from the surveys were that water quality management should consider the use of moving averages or composites of a period of hours to minimize impacts of short-term variations in ambient turbidity measurements.

Water quality management should also account for potential influence of seasonal changes, precipitation, and the presence of outfalls through appropriate placement of upstream and downstream monitoring points. Under ambient conditions, TSS and turbidity correlated well for data collected from the LRROC and this relationship suggests that it is possible to use turbidity to access compliance with a TSS criterion. However, it is not known whether TSS associated with other disturbances, such as vessel propeller wash (propwash), with higher turbidity values will demonstrate the same relationship. Specific results of turbidity and TSS studies are available in the PDI Report

3.2.8 Utility Mapping

A field utility survey within the dredge footprint was completed for the PDI, with specific focus on utilities that were identified by the desktop survey. Using advanced electromagnetic locating systems and acoustic sub-bottom profilers in conjunction with survey-grade sonar and global positioning system (GPS), DoC Mapping, a subcontractor to the design engineering team, performed surveys of the suspected locations of 16 utilities.

Location of the 16 utilities were based on the desktop evaluation of historical records performed as part of the PDI (Appendix C) and included both the suspected locations and

Lower Rouge River — Old Channel 19 130287-03.01 areas immediately adjacent. DoC Mapping was able to obtain positions and depth-of-cover readings for 12 individual utilities. Of the remaining four, one could not be surveyed because it is thought to lie directly beneath the Zug Island Road Bridge. Surveys were performed for the other three suspected utilities using multiple survey techniques but did not find evidence of utilities present.

This design does not indicate or imply that lack of evidence of suspected utilities from the survey fully supports a conclusion that they are absent. The desktop study (Appendices K and L of the PDI Report) upon which the PDI utilities survey was based and the full report of findings for surveyed utilities (Appendix Q of the PDI Report) was used in planning the RD for dredging, capping, and permanent sheet pile wall design. The utility surveys have been provided as a basis for design and as useful information for planning implementation. The Sheet Pile Wall Contractor and the GLNPOCS Contractor will independently verify the utility survey information provided in this BODR prior to initiating activities.

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4 DELINEATION OF REMEDIAL BOUNDARIES

A weight-of-evidence approach using data collected during the RI/FS and PDI efforts (see Section 3) was used to develop an optimal and effective delineation of the lateral and vertical extents of contamination exceeding the RALs. Data from the PDI used in the delineation are included in the PDI Report. Section 2 presents the basis for the RALs, which are briefly summarized below.

Sediments exceeding one or more of the following RALs were targeted for remediation:

• Surface sediments (0- to 1-foot depth) with an IWTU greater than 5

• Subsurface sediments (great than 1-foot depth) with an ESBTU greater than 7.5

• NAPL at any depth interval

The IWTU directly reflects PAH bioavailability in porewater and provides the best estimate of benthic toxicity relevant to PAHs in sediment. All surface sediment samples collected as part of the RI/FS and PDI were subjected to porewater analysis. The ESBTU is based on the partitioning of PAH compounds between the TOC in bulk sediment and the porewater, and an expected porewater concentration is calculated. The ESBTU was used as the RAL for subsurface sediment because porewater analyses were not performed for subsurface sediments.

Details of the remedial boundary development are provided in the following subsections.

Sections 7.3 and 7.7 discuss the development of dredging and capping designs, respectively, to remediate the sediments within the delineated remedial boundaries.

4.1.1 Lateral Extents of Contamination

The lateral extents of contamination were initially defined by inspecting core data. Samples collected from 237 locations during site investigations dating back to 2010 were reviewed and mapped with geographic information system (GIS) software. Thiessen polygons were developed around each core as a way to delineate the influence of data from individual cores to a larger surrounding area (i.e., the properties throughout each polygon are represented by a single core at the center of the polygon).

Delineation of Remedial Boundaries

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Initially, the remedial boundaries were delineated to include all polygons that exceeded one or more of the RALs. However, the RD team concluded that delimiting areas for remediation should be based on a variety of factors, including not only the numeric RALs for IWTU and ESBTU, but also reasonable uncertainty bounds of those values…