Howards Bay_2020 Certified Final - RTA_ DDR_1 of 2.pdf

USACE, Detroit District

100% DESIGN DOCUMENT

REPORT, GLLA SEDIMENT

CLEANUP IN HOWARDS BAY,

SUPERIOR, WISCONSIN

Contract No. W911XK-16-C-0019

January 24, 2020

100% DESIGN DOCUMENT REPORT

arcadis.com G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx

100% DESIGN

DOCUMENT REPORT,

GLLA SEDIMENT

CLEANUP IN

HOWARDS BAY,

SUPERIOR,

WISCONSIN

Prepared for:

U. S. Army Corps of Engineers

Detroit District

Contract No. W911XK-16-C-0019

Prepared by:

Arcadis U.S., Inc.

One Lincoln Center

110 W Fayette St #300

Syracuse, NY 13202

Tel 315 446 9120

Fax 315 449 0017

Our Ref.:

16935001.0000

Date:

January 24, 2020

Mark Gravelding

Lead Engineer

Wisconsin PE #44865

Heather VanDewalker

Quality Assurance Manager

Sarah A. Hill

Project Manager

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx

CERTIFICATION

I, Mark O. Gravelding, P.E., hereby certify that I am a registered professional engineer in the State of

Wisconsin, registered in accordance with the requirements of ch. A-E 4, Wis. Adm. Code; that this document has been prepared in accordance with the Rules of Professional Conduct in ch. A-E 8, Wis.

Adm. Code; and that, to the best of my knowledge, all information contained in this document is correct and the document was prepared in compliance with all applicable requirements in chs. NR 700 to 726, Wis. Adm. Code.

Mark O. Gravelding, P.E. (WI# 44865)

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx

VERSION CONTROL

Revision No Date Issued Description Reviewed by

0 03/20/2017 95% Draft submitted for ITR review M. Gravelding, D. Cowin, S. Hill

1 04/07/2017 95% Draft submitted for Partner review M. Gravelding, D. Cowin, S. Hill, ITR

2 05/12/2017 Responses to Partner comments in preparation for May 17, 2017 design review conference

M. Gravelding, S. Hill

3 08/18/2017 100% document submitted for Partner review

M. Gravelding, H. VanDewalker, S.

Hill, ITR

4 11/26/2018 100% document submitted for Partner approval

M. Gravelding, H. VanDewalker, S.

Hill, ITR

5 01/24/2020 Finalize document incorporating Partner comments

Note: H. VanDewalker replaced D. Cowin as the Quality Assurance Manager in May 2017.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx i

CONTENTS

Certification .................................................................................................................................................... ii

Acronyms and Abbreviations ........................................................................................................................ iv

1 Introduction

1.1 Purpose

1.2 Report Organization

1.3 Project Description and Existing Conditions

1.3.1 Site Description

1.3.2 Summary of Sediment Investigations and Areas of Contamination

1.3.3 Benthic Community and Toxicity Tests

1.3.4 Remedial Action Objectives and Description of Remedial Action

2 Basis of Design and Key Design Elements

2.1 Summary of Pertinent Data

2.2 Modeling Summary

2.2.1 EVS Model Procedures

2.2.2 Placement Criteria Evaluation and Procedures

2.2.3 EVS Model Output Summary

2.2.4 Placement Evaluation Results

2.3 Dredge Prism Development

2.4 Access and Permits

2.5 Mobilization and Site Preparation

2.5.1 Mobilization

2.5.2 Survey

2.5.3 Utility Clearance

2.5.4 Staging Areas

2.5.5 Community Air Monitoring

2.5.5.1 Monitoring Requirements

2.5.5.2 Action Levels

2.5.6 Turbidity Monitoring

2.6 Dredging

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx ii

2.6.1 General Approach

2.6.2 Debris Removal

2.6.3 DMU Sequencing

2.6.4 Engineering Controls

2.6.5 Confirmation Sampling

2.7 Residuals Cover

2.7.1 General Approach

2.7.2 Engineering Controls

2.8 Enhanced Natural Recovery

2.8.1 General Approach

2.8.2 Engineering Controls

2.9 Material Handling

2.9.1 Debris Handling and Disposal

2.9.2 Dredged Material Handling and Placement

2.9.3 Water Handling and Treatment

2.10 Project Completion

2.10.1 Decontamination

2.10.2 Upland Restoration

2.10.3 Post-Construction Survey and Sampling

2.10.4 Demobilization

2.11 Safety Considerations

3 Quantity and Cost Estimates

4 Technical Review Documentation

5 References

TABLES

1 Preliminary Remedial Goals (in text)

2 Summary of Changes to Dredge Management Units

3 Estimated Top of Sediment and Clay Elevations

4 Remedial Design Units and Estimated Quantities

5a Wisconsin Point Landfill Placement Evaluation

5b List of Samples Included in Arithmetic Average Calculations for Each Dredge Management Unit

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx iii

5c Average Concentration for Contaminants of Concern in Each Dredge Management Unit

6 Summary of Required Permits (in text)

7 Air Quality Action Levels and Response Actions

FIGURES

1 Site Location Map

2 Site Areas and Main Features

3 Summary of Analytical Data – Area 1

4 Summary of Analytical Data – Area 2

5 Bathymetric Surface

6 Example EVS Model Output (in text)

7 Proposed Staging Areas

8 Proposed Off-Site Placement Locations

APPENDICES

A Sediment Core Logs

B Wisconsin Department of Natural Resources Communications

C Calculations

D Decision Tree

E Technical Review Documentation

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx iv

ACRONYMS AND ABBREVIATIONS

AOC Area of Concern

Arcadis Arcadis U.S., Inc.

BOD Basis of Design

BUIs Beneficial Use Impairments

CBSQG Consensus-Based Sediment Quality Guidelines

City City of Superior

CS Cummings Slip

COCs contaminants of concern cy cubic yards

DMU dredge management unit

Draft DDR Draft 65% Design Document Report

DSR Sediment Data Summary Report

ENR enhanced natural recovery

EVS Earth Volumetric Studio

FC Federal Channel

FFS Focused Feasibility Study for Sediment Cleanup in Howards Bay

FOS factor of safety

FP Frog Pond

Fraser Fraser Shipyards, Inc.

FS Fraser Slip

GLLA Great Lakes Legacy Act

GLNPO Great Lakes National Program Office

HB Howards Bay

HS Hughitt Slip

IGLD 85 International Great Lakes Datum of 1985

IJC International Joint Commission

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx v

ITR Internal Technical Review

LEL lower explosive limit

LWD low water datum

MEC midpoint effect concentration mg/kg milligrams per kilogram mg/kg-TOC% milligrams of organic constituent per kilogram of dry-weight sediment normalized at 1% total organic carbon

MPCA Minnesota Pollution Control Agency

NAD83 North American Datum of 1983

NAVD88 North American Vertical Datum of 1988

NTU nephelometric turbidity units

PAH polycyclic aromatic hydrocarbon

Partners Howards Bay Project Partners

PEC probable effect concentration

PID photoionization detector

PM10 particulate matter less than 10 microns in diameter

PRG Preliminary Remedial Goal

P&S 65% Plans and Specifications

RA Remedial Action

RAO Remedial Action Objective

RAP Remedial Action Plan site Howards Bay

SLRAOC St. Louis River Area of Concern

SND strategic navigation dredging

SPI sediment profile imagery

TEC threshold effect concentration µg/kg micrograms per kilogram

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx vi

USACE United States Army Corps of Engineers

USEPA United States Environmental Protection Agency

WDNR Wisconsin Department of Natural Resources

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 1

1 INTRODUCTION

Arcadis U.S., Inc. (Arcadis) has prepared this 100% Design Document Report (DDR) for the Great Lakes

Legacy Act (GLLA) sediment cleanup project in Howards Bay, located in the City of Superior in Douglas

County in northwest Wisconsin (site; Figure 1). This DDR was prepared under contract W911XK-16-C-

0019 to the United States Army Corps of Engineers (USACE) Detroit District and in coordination with the

Howards Bay Project Partners (Partners), which include the United States Environmental Protection

Agency (USEPA) Great Lakes National Program Office (GLNPO), the Wisconsin Department of Natural

Resources (WDNR), the City of Superior (City), and Fraser Shipyards, Inc. (Fraser). The USACE is providing technical and engineering support to USEPA for this project.

This document presents the basis for the environmental dredging and cover design for sediment cleanup in Howards Bay. This DDR has been prepared in general accordance with: 1) USACE Engineer

Regulation (ER)-1110-2-1150; 2) the Focused Feasibility Study for Sediment Cleanup in Howards Bay

(FFS; Arcadis 2015); and 3) applicable USEPA guidance for contaminated sediment remediation (USEPA

2005). The remedial action (RA) activities described in this DDR were designed considering that federal navigation channel maintenance will be completed by the USACE as “Strategic Navigation Dredging”

(SND), which is linked to the cleanup of contaminated sediment that is addressed in this DDR. Funding for the SND is provided under the Great Lakes Restoration Initiative, is contingent on the cleanup of the contaminated sediment in Howards Bay, and will be implemented in concert with the environmental dredging.

The elements of the project that are unique to the environmental dredging are described and developed herein and in the drawings and specifications, referenced herein and prepared under separate cover. The

USACE will separately prepare the design drawings and specifications for the SND project. It is anticipated that the two designs will be combined by USACE as one set of contract documents and bid as one contract. This document will be provided as reference to the Contractor; however, the environmental dredging technical specifications and design drawings are considered the contract documents and supersede information in this document.

1.1 Purpose

The RA activities are proposed to remediate impacted sediment and restore Howards Bay to ultimately achieve removal of beneficial use impairments (BUIs) identified for the St. Louis River Area of Concern

(SLRAOC). Impacted sediments in Howards Bay potentially contribute to the following BUIs listed for the

SLRAOC (Stage I Remedial Action Plan [RAP], Minnesota Pollution Control Agency [MPCA] and WDNR

1992):

• BUI 1: Fish Consumption Advisories

• BUI 3: Fish Tumors and Other Deformities

• BUI 4: Degradation of Benthos

• BUI 5: Restrictions on Dredging

• BUI 9: Loss of Fish and Wildlife Habitat

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 2

The project designed in this report is a refinement of the alternative that was selected by consensus among the project Partners with the recognition that areas, volumes, and other details would be refined during design (Partners 2015). Refer to Section 1.3.4 for a description of the selected alternative.

1.2 Report Organization

The organization of this DDR is presented as follows.

Section Description

1 – Introduction

Presents the purpose of the DDR, summarizes the report organization, provides a description of site conditions, presents a description of the site characterization and nature and extent of environmental impacts, and outlines the remedial action objectives (RAOs) and the remedial action.

2 – Basis of Design Presents the process and tools used to identify design components.

3 – Quantity and Cost

Estimates

Provides the remedial areas and volumes, placement volumes, and summarizes the cost estimates to implement the remedial action.

4 – Technical Review

Documentation

Presents the technical reviews conducted by staff not associated with the direct design of the project but have qualifications to accomplish the required work.

5 – References Lists sources used to prepare this report.

Five appendices are included herein to supplement the contents of this DDR. These appendices provide additional information related to the implementation of the RA activities and include the following:

• Sediment Core Logs (Appendix A);

• Wisconsin Department of Natural Resources Communications (Appendix B);

• Calculations (Appendix C);

• Decision Tree (Appendix D);

• Technical Review Documentation (Appendix E).

Additionally, technical specifications and design drawings are generally referenced throughout this DDR.

These documents have been prepared under separate cover and will be the basis for the contract documents and supersede information contained in this document.

1.3 Project Description and Existing Conditions

This section provides a summary of the site background and history, as well as the site characterization, nature and extent of environmental impacts, and the RA.

1.3.1 Site Description

Howards Bay is a priority area for remediation within the larger SLRAOC, in the City of Superior, Douglas

County, Wisconsin (Figure 1). It has been the home of a series of shipyards, grain terminals, commercial fishing operations, and other industrial operations for over 100 years. It is located on the east side of the

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 3

St. Louis River, and is bisected by the Interstate 535 (I-535) Bridge (Blatnik Bridge) crossing over Howards

Bay. The Howards Bay study area includes the bay proper and three ship slips constructed along the south shore – the Fraser Slip (FS), Cummings Avenue Slip (CS), and Hughitt Avenue Slip (HS) – in addition to two dry docks along the south shore. The area at the head of Howards Bay is referenced as the Frog Pond

(FP). Until this design, the site was divided into Area 1 and Area 2. For purposes of design and construction, this division is no longer necessary; however, a description of the breakdown can be found in the FFS

(Arcadis 2015). The approximate size of the Howards Bay study area, including the three slips, is about

300 acres.

Several shoreline types are present around the bay and the associated slips, including sheet pile, rip-rap, former wooden and concrete wharf structures (some of which are dilapidated), existing and former bridge approaches and abutments, and earthen banks. These features are shown on Figure 2. Water depths in

Howards Bay vary from shallow along the north shore to approximately 33 feet below the Lake Superior low water datum (LWD) within the federal channel (FC) that runs nearly the entire length of the bay. The

Lake Superior LWD is at an elevation of 601.1 feet using the International Great Lakes Datum of 1985

(IGLD 85).

Commercial maritime needs in the bay are met by the federal navigation channel and access to the ship slips and dock areas. The federal channel ranges from approximately 100 to 275 feet wide with an authorized project depth of 27 feet below LWD (elevation of 574.1 feet) in the project area. Fraser, the

City of Superior, and CHS Inc. own the large majority of land bordering Howards Bay. The Hughitt

Avenue Slip is used for loading and unloading ships at the CHS Inc. grain elevators, and the Sivertson

Fisheries docks and boats are situated at the south end of the slip. The Cummings Avenue Slip has most recently been used by Fraser for long-term layup of ships and by Lake Assault Boats LLC for launching small, aluminum craft. Fraser also has installed a boat ramp in the southern end of the slip. Uses during construction by others are expected to be limited to mooring for work barges and smaller craft in approximately the northern one third of the slip. The Fraser Slip is used by Fraser and local law enforcement for docking smaller boats and this is also the intended use for the future. Additional information on land ownership and use is provided in Section 2.4.

An outfall discharges stormwater drainage from the City of Superior into Cummings Slip and a drainage ditch functions as a tributary at the far east end of Howards Bay. Additional stormwater outfalls exist in

Fraser Slip and the Hughitt Slip. Stormwater runoff from the Blatnik Bridge may enter Howards Bay as well (WDNR 2015).

At the time the FFS was undertaken, the former Baxter Avenue Embayment which consists of an area along the south shore of Howards Bay between the Cummings and Fraser Slips was open water;

however, the embayment is no longer part of the project area. The area was infilled in 2016 and isolated from the bay with a sheet pile bulkhead through a separate project to create additional ship berthing space along the federal channel. The area along the bulkhead will be utilized for staging and processing as part of the RA activities.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 4

1.3.2 Summary of Sediment Investigations and Areas of Contamination

A summary of the findings of sediment sampling activities conducted at the site in 2007, 2010, 2013, and

2014 is provided in the FFS and the Howards Bay Sediment Data Summary Report (DSR; Arcadis 2014).

Additional sampling was conducted in 2015 and these data have been included in the basis of design

(BOD) provided herein to refine the RA horizontal and vertical boundaries. The sediment data collected in

2007, 2010, 2013, 2014, and 2015 provide a refined understanding of the nature and extent of contamination at the site. The combined data sets include more than 500 sediment data points from approximately 160 attempted core or grab sample locations in Howards Bay. Additional samples were collected and analyzed in 2016 to characterize the SND material for disposal; however, these data are not germane to the RA and are not included in this DDR.

Based on a 2011 report prepared for USEPA (Weston 2011) to summarize data collected in 2010, polycyclic aromatic hydrocarbons (PAHs), tributyltin, and lead were identified as contaminants of concern

(COCs; Partners 2014). USEPA and WDNR requested consideration of mercury as an additional COC as part of the DSR and the FFS. Concentrations of the COCs vary within Howards Bay sediments due to the history of various sources, dredging activity, construction projects and other activities within the bay, including but not limited to ship movements and ice breaking. As described in the DSR, the site sediment sample data were compared to the WDNR recommended sediment quality guidelines (WDNR 2003), including Threshold Effect Concentration (TEC) and Probable Effect Concentration (PEC) screening levels, which are levels at which the potential for toxicity to benthic organisms are predicted to be unlikely and probable, respectively. The Midpoint Effect Concentration (MEC) is the average of the TEC and PEC values. In comparison to the WDNR MEC values, the largest potential exposures to concentrations of the project COCs in surface sediment occur as follows: in the Cummings Avenue Slip, Fraser Slip, and east end of Howards Bay for lead; in the Cummings Avenue Slip and Hughitt Avenue Slip for mercury; at the head of the Cummings Avenue Slip and near the Blatnik Bridge for PAHs; and in the Hughitt Avenue Slip, adjacent to the Hughitt Avenue Slip in the federal channel, and near the head (i.e., west end) of the federal channel for tributyltin. The COC mass and associated volume of sediment represented by each sediment core with concentrations exceeding selected comparison values (that include the WDNR screening levels) provided an indication of relative mass distribution within the site (see Figure 4-8 of the

DSR). COC mass inventories are concentrated in the three slips, in the southeastern end of the bay, in the head of the federal channel, and along the immediate margins of the federal channel. In the shallower water, north of the federal channel, there are large areas with comparatively little COC mass inventory.

Data gaps were identified during development of the design. Additional sampling was conducted in June

2017 by USEPA and WDNR. Results of these sampling activities were summarized in a memorandum drafted by WDNR and reviewed by the Partners (Appendix B). The data were used to refine the BOD between the 65% and 95% design phases.

1.3.3 Benthic Community and Toxicity Tests

As described in the FFS, human health and ecological risk assessments have not been completed for

Howards Bay. Recreational contact with sediments as a result of wading (for example by fisherman) or other incidental contact with sediment along the north shore for the site is possible. Worker contact with sediments could occur in association with marine construction activities in the bay and shipyard activities, G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 5 such as contact with anchors and other equipment or during dry-dock cleanout activities (removal of small amounts of sediment that may come in with bay water when ships are taken into dry-dock).

Ecological exposures may occur through the benthic community and could include higher level receptors that may accumulate bioaccumulative compounds through the food chain. Toxicity tests conducted with the crustacean Hyalella azteca and the insect Chironomus dilutus were performed to determine whether chemicals were present in the Howards Bay sediment at concentrations that would be harmful to the test organisms. These tests indicated spatially limited adverse effects on the benthic community of Howards

Bay in comparison to reference and control samples, with the exception of one sample which resulted in genotoxicity to the bacterium Vibrio fischeri (see DSR for additional details on test results). This sample was located within Fraser Slip. A limited number of toxicity tests were conducted within the study area.

Because of the variability among sample results, there is high uncertainty with respect to the representativeness of toxicity data for the whole study area.

Results of the benthic sampling described in the DSR showed a macroinvertebrate community that is typical of finer-grained sediments with organisms that often “burrow” in finer sediments, such as oligochaetes (39 percent [%] segmented worms), dipterans (36% fly larva) and nematodes (14% roundworms). The Partners decided that efforts to interpret the benthic community data relative to background, to evaluate the data with respect to need for remediation, or to use these data to develop potential remedial endpoints would not be undertaken for the purposes of this GLLA project. However, it was acknowledged that these data may be useful for post-cleanup comparisons at a future date if adequate data analysis is undertaken to control for sources of variability.

1.3.4 Remedial Action Objectives and Description of Remedial Action

This section summarizes the RAOs provided in the FFS, as well as the RA to be implemented to support achievement of these objectives.

As identified in the FFS, the following RAOs were developed for the COC-impacted sediments in

Howards Bay:

1. Reduce potential for human health risks associated with exposure to COCs through direct contact with sediments and incidental sediment ingestion.

2. Reduce potential for risks to benthic organisms.

3. Reduce potential for risks to other organisms (fish, birds, mammals, etc.).

4. Reduce sediment concentrations of COCs to ultimately meet criteria, standards, and guidelines per

International Joint Commission (IJC) and AOC RAP documents.

5. Reduce the potential for contaminated sediment within Howards Bay to act as a source of contamination outside of Howards Bay in the St. Louis River Estuary.

MEC values were adopted as preliminary remedial goals (PRGs) for the project COCs. In formulating remedial alternatives, consideration was given to the degree to which PRGs were exceeded in the deeper sediments below the uppermost sample layer, specifically in comparison to whether the PEC value was

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 6 also exceeded and the depth intervals within which the exceedances were observed. The following table lists the sediment PRG value for each COC:

Table 1. Preliminary Remedial Goals

COC Sediment PRG Value

Total PAHs 12.2 mg/kg-TOC%

Tributyltin 0.0017 mg/kg-TOC%

Lead 83 mg/kg

Mercury 0.64 mg/kg

Notes: mg/kg = milligrams per kilogram; mg/kg-TOC% = milligrams of organic constituent per kilogram of dry-weight sediment normalized at 1% total organic carbon

The FFS identified and assessed a total of eight alternatives based on seven evaluation criteria (Arcadis

2015), and the Partners agreed on selection of Alternative A-4 as the preferred alternative due to moderate to high scorings on the criteria evaluated. Alternative A-4 includes sediment removal in refined dredge management units (DMUs), except for enhanced natural recovery (ENR) in Units 15D and 25B and No Action in Units 12B, 13B, 14B, 15B-C, 17B-C, 19A, 20, 22, 25A, 28. The Partners agreed that associated dredge limits and costs of Alternative A-4 would be refined in the remedial design phase. A preliminary revision to Alternative A-4 was completed in September 2015 to account for the 2014 and

2015 sample results, which were not considered in the FFS (Partners 2015). This preliminary revision included adjustments to the DMU boundaries, removal depths, and intended remedial action. Table 2 summarizes the changes to the DMU nomenclature following the FFS, and the current layout of DMUs is provided herein as Figures 3 and 4. Further DMU refinement conducted during the design process is discussed in Section 2.2.

Alternative A-4 considers that USACE is responsible for dredging sediments within the federal channel to achieve the SND authorized project depth of 27 feet below LWD (elevation of 574.1 feet) plus 1-foot of overdepth (elevation of 573.1 feet). The RA activities described herein address contaminated sediments that exist in some areas at elevations below the SND dredging limits as well as the contaminated sediments outside of the federal channel boundaries. The final elevation will be confirmed following completion of the SND dredging, and the environmental dredge design in these areas will be reevaluated as needed. For example, DMUs FC-7 and FC-11 are considered as “no action” areas based on the assumption that the impacted sediment in these units will be removed by the SND dredging. If SND overdepth removal does not proceed to sufficient elevations in these DMUs based on the bottom elevations of known impacts, additional dredging may be required during the environmental phase.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 7

2 BASIS OF DESIGN AND KEY DESIGN ELEMENTS

As discussed in Section 1.3.4, the Partners agreed on refining the dredge limits of Alternative A-4 during the remedial design efforts. This section describes the process used to refine the dredge limits of

Alternative A-4 and the general dredging approach for the RA activities, as well as the approach for the

ENR areas, material handling, and safety considerations. The following items are discussed in this section, which includes the BOD and key design elements:

• Summary of pertinent data

• COC modeling summary

• Dredge prism development

• Access and permits

• Mobilization and site preparation

• Dredging

• Residuals cover

• ENR

• Material handling

• Project completion

• Safety considerations

2.1 Summary of Pertinent Data

The COC data, 2013, 2014, and 2015 bathymetry survey data, and top of sediment and top of clay elevation data for the core locations collected in 2007, 2010, 2013, 2014 and 2015 were used to refine the dredge limits of Alternative A-4 using the software Earth Volumetric Studio (EVS) from C Tech

Development Corporation. Data from cores collected in 2017 were incorporated after the EVS model was complete as part of the dredge prism development (see Section 2.3).

The COC data compared to the MEC from the sediment sampling activities conducted at the site in 2007, 2010, 2013, 2014, and 2015 are shown on Figures 3 and 4. Additional sample locations and data from the 2017 sampling event are included in Appendix B. Harbor-wide bathymetry survey data from 2015 have been used in combination with survey data from 2013 and 2014 where 2015 survey data were not available. The survey data were collected and provided by USACE. The combined bathymetry data as generated using the EVS software are shown on Figure 5. This combined bathymetry surface prioritized the most recent survey information, and then supplemented with the older data as needed.

The project area is underlain by a distinct unit of native clay that is denser than the overlying soft sediment and where COC concentrations are less than RAOs; thus, the clay layer serves as a confining layer. Top of sediment elevation and top of native clay elevation data are provided in Table 3 for samples collected within the proposed work area. The core logs are included as Appendix A. Note that core logs were not recorded for samples collected in 2017; rather, sampling information was documented in a

WDNR memorandum (Appendix B).

Not all core samples contained a plug of native red clay at the bottom – some cores met with refusal without recovering native clay (the native clay may have been too stiff or fallen out of the core or the core

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 8 tube could have encountered other dense material limiting its advancement). Approximately 30% of the sampling locations encountered the native red clay layer. Top of native clay elevations were estimated using top of sediment elevation and sediment coring field notes and core logs. Core stratigraphy logs indicate the approximate thickness (0 to 14 feet) of the sediment layer in the core tube overlying the plug of native red clay in the bottom of the core when it was present.

In general, the amount of sediment in the core samples is interpreted to be approximately equal to the thickness of soft sediment above native clay, where native clay is present1. Where native clay was not present, the total thickness of sediment was not inferred from core logs. Based on the top of sediment surface elevations assigned to each core and core stratigraphy logs, the bottom-of-sediment/top-of-native-clay elevation was established for each core with the native clay layer (Table 3). Based on the difference between this bottom-of-sediment/top-of-native-clay and the bathymetry, the estimated sediment thickness at each of these core locations was calculated. These data have high uncertainty in some areas, especially along the sides of the federal channel where bed slopes are greatest and core sampling was limited.

2.2 Modeling Summary

EVS software was used to refine the dredge limits of Alternative A-4 by creating a three-dimensional visualization of the removal areas to confirm removal limit assumptions. Detailed information regarding the software can be found at the manufacturer’s website: http://www.ctech.com/products/earth-volumetric-studio/.

2.2.1 EVS Model Procedures

The following procedures were used in setting up and running the model to initially define and visualize removal areas. Once the dredging boundary conditions were defined, the design shifted from EVS to

Microstation/Terramodel for development of the dredge prism, as discussed in Section 2.3.

Model setup:

• Bathymetric survey data collected by USACE in 2013, 2014, and 2015 were loaded into the model. An order of precedence was set to use the most recent survey data available in a given location.

• The sediment core locations were input with the top of core elevation for each location set as the sediment elevation at the time the core was collected. The elevation of each core strata and corresponding COC data were incorporated based on the top of core elevation at the time of collection and the representative core intervals (not from the bathymetric surface in the model).

• DMU boundaries were added to the model. The horizontal boundaries were taken from the revised Alternative A-4 figures (Partners 2015), with further refinements made along the shoreline to reflect site conditions (see Figures 3 and 4).

1 While using the measured recovered core sediment thickness provides a reasonable estimate of the actual in-situ sediment thickness for purposes of the design, the measured thickness may not be representative of the full, actual sediment thickness due to sampling limitations such as potential material compression or angled penetration of core tube into the bed.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 9

• The vertical boundaries within the federal channel were set as the SND dredge elevation +1 foot overdepth (573.1 feet IGLD 85).

Model runs:

• The analytical data for the primary COCs (TPAH, TBT, lead, and mercury) were interpolated for the entire site using a Kriging method to generate a three-dimensional representation of the contaminant distribution (3D distribution) in the sediment bed and channel slopes.

• The core data were categorized as either having at least one COC above its MEC or no COCs exceeding an MEC. All COCs were treated as equal in identifying removal limits.

• The 3D Kriged chemical distributions were compared to the analytical core data, highlighting regions where any COC exceeded the MEC.

• The DMU areal boundaries were overlaid on the Kriged 3D distributions to isolate these areas for further evaluation and identify potential boundary modifications.

• The vertical extent of the Kriged 3D distributions were evaluated as follows:

o Kriging was used to identify the bottom elevation of MEC exceedances (i.e., the elevation of contamination) for all DMUs. This step used both cores inside and outside of the DMU.

o Top of native clay elevations, as determined from the core logs (Table 3), were added to the model where available. Interpolated clay elevations were applied to the DMU to refine the vertical extent. If the Kriged bottom elevation of MEC exceedances was above the interpolated clay elevation, then the bottom elevation of MEC exceedances was used as the extent of removal; if the Kriged bottom elevation of MEC exceedances was below the interpolated clay elevation, then the interpolated clay elevation was identified as the deepest elevation of contamination.

o DMUs where MEC exceedances were observed at the bottom of the core and where there was no clay surface to bound the bottom elevation were evaluated on a case-by-case basis to review the Kriged bottom elevation. If the bottom elevation extended below the core but was supported by non-MEC exceedance data from adjacent cores, then this elevation was used as the extent of removal; if the surrounding cores all had MEC exceedances to the bottom of the core, then the bottom elevation was interpolated from the other sediment cores within the DMU.

Results from the modeling procedure provided above were reviewed by the Partners preliminarily to comment on the boundaries and identified elevations. Adjustments were made based on this interim review, and these adjusted removal area and elevations were used to develop the EVS model output as described in Section 2.2.3.

2.2.2 Placement Criteria Evaluation and Procedures

The COC concentrations in the refined DMUs, including the additional data collected in 2017, were compared to the Wisconsin Point Landfill placement criteria (Appendix B) to identify remedial dredging material suitable for disposal at this facility. For the material determined to be suitable for placement at

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 10

Wisconsin Point Landfill, an additional comparison was also performed to identify material that could be used as cover instead of subsurface fill. Remedial dredging material not acceptable for placement at

Wisconsin Point Landfill will be placed at another offsite facility (i.e., Vonco Landfill in Duluth, Minnesota – see Section 2.9). SND material will be sent to the USACE’s Erie Pier facility for disposal. The procedures outlined below were used in performing the placement criteria evaluation. The analysis was conducted using output from the EVS model and Microsoft Excel for the calculations.

• Screening was conducted only for sediment sample intervals that lie within the DMU boundaries.

• The Wisconsin Point Landfill placement criteria are provided in Appendix B. Specifically, the placement criteria are provided in Table 1 of the document “Site-Specific Residual Contamination

Levels (RCLs) for Dredged Material from Howards Bay Proposed for Placement at the Closed

Wisconsin Point Landfill in Superior, Wisconsin” dated April 19, 2017 (Appendix B), and the criteria of 5 times the values provided in Table 1 were used as screening criteria.

• Arithmetic average concentrations of the samples that lie within each individual DMU boundary

(area and top/bottom elevation) were calculated and compared against the Table 1 criteria and 5 times the Table 1 criteria.

• Each DMU and associated volume was classified as follows:

o Acceptable for surface cover: Arithmetic average of the samples that lie within individual

DMU boundary for all COCs did not exceed criteria in Table 1. In addition, and in accordance with Wisconsin Administrative Code Chapter NR 720, the cumulative excess cancer risk did not exceed 1x10-5 and the hazard index for non-carcinogens did not exceed 1.

o Acceptable for subsurface cover: Arithmetic average of the samples that lie within individual DMU boundary for all COCs did not exceed 5 times criteria in Table 1.

o Not acceptable for placement at Wisconsin Point Landfill placement: Arithmetic average of the samples that lie within individual DMU boundary exceeded 5 times criteria in Table

1 for one or more of the COCs.

2.2.3 EVS Model Output Summary

The three-dimensional model files generated from the EVS software were used to determine the design approach (refer to Table 4) and initial removal extent for each DMU. These files included the footprint

(i.e., horizontal limits) and target removal elevation (i.e., target dredge surface based on elevation of contamination) for each DMU. A screenshot of the typical model output is shown below (see Figure 6).

The blue lines indicate DMU boundaries in plan view, the blue columns represent sample locations where

COCs are below removal criteria, the orange columns represent sample locations where COCs are above removal criteria, the orange/brown octagons indicate the lowest extent of exceedances, and the grey squares indicate the presence of a clay layer.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 11

Figure 6. Example EVS Model Output

Table 4 summarizes the approach used for each DMU and the corresponding estimated in-situ removal volume. Final DMU areas and elevations from the EVS model were exported to Terramodel for further engineering evaluations (e.g., considerations of stability, sloping, etc.) and then to Microstation for the creation of the Contract drawings as discussed in Section 2.3.

2.2.4 Placement Evaluation Results

Results of the placement evaluation are provided in Tables 5a through 5c. Table 5a provides a breakdown of those DMUs that meet or exceed the various criteria, with the “All COCs” (orange column) aggregating all the comparisons and summarizing the in-place volumes associated with each comparison. Table 5b summarizes the input data for the evaluation, and Table 5c summarizes the average concentrations by DMU.

The output of the placement analysis indicated that the majority of dredged material to be removed as part of the GLLA project can be sent to the Wisconsin Point Landfill for placement (SND dredged material will go to the Erie Pier facility). A total of 27 DMUs are acceptable for surface cover (approximately 44,400 neat-line cubic yards [cy]), 8 DMUs are acceptable for subsurface cover (approximately 12,000 neat-line cy), and 3 DMUs (approximately 8,300 neat-line cy) will require disposal at another offsite facility. These neat-line quantities do not include overdepth or bulking assumptions.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 12

2.3 Dredge Prism Development

Dredge Prisms

For construction, the Contractor will be provided with a set of removal grades to be achieved as part of the RA, which are also referred to as a dredge prism (see drawings package provided under separate cover). The EVS model and information summarized in Table 4 were used to develop dredge prisms for construction using the following procedures:

• The final EVS removal limits (horizontal and vertical removal surfaces) were imported to

Terramodel for use as the starting point for the prism.

• The proposed SND dredge prism based on EVS model, including an assumed 1 foot of overdepth was incorporated.

• Boundaries were adjusted based on the stability evaluation (Appendix C). This included adjusting horizontal boundaries of DMUs where setbacks will be required due to structural considerations

(e.g., existing sheet pile, foundations, shoreline conditions, etc.), as well as an evaluation of existing (pre-dredging) slopes adjacent to the navigational channel in proposed dredge areas to determine if dredging is feasible and/or safe. Note that the 1963 dredging information was referenced to assist in this evaluation, and the final side slopes commonly were in the range of 1-

1.5:1 (horizontal:vertical).

• Sloping was applied to the perimeter of DMUs based on the stability evaluation. This included determining the required dredge slope through the geotechnical evaluation for slope and shoreline stability. The required slope was then applied starting from the bottom of the DMU (the target dredge elevation) and extending out beyond the defined DMU boundary. In instances where adjacent features prevented sloping outside of the defined DMU boundary (e.g., adjacent obstruction, required offset, etc.), sloping started at the edge of the defined DMU boundary and sloped into the DMU.

• Removal grades were adjusted within the DMU for constructability (i.e., smooth dredge prism contours and transitions).

• Once the above procedures were implemented, select cross-sections were cut through the

DMUs. These cross-sections are provided in the drawings package provided under separate cover.

For slope stability, a maximum of 2:1 (horizontal:vertical) side slopes along dredge cuts was determined based on USACE’s intended practice for the SND work, site sediment properties, and common environmental dredging design practices. The 1963 dredging information showed steeper slopes were achieved post dredging, suggesting the proposed slope or steeper may be achievable. A maximum 3:1

(horizontal:vertical) slope would be required to provide a stable final grade for residual cover material

(sand) based on the angle of repose of this material and additional considerations for fully saturated conditions. Sands have a minimum angle of repose of 27 degrees in their loosest state (Das 1997), and a factor of safety (FOS) of 1.5 or greater should be included in the design. The proposed slope is equivalent to 18.5 degrees. The FOS is calculated as:

FOS = tan(soil angle of repose) / tan(slope angle) = tan (27) / tan(18.5) = 1.52.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 13

The Partners discussed that the preferred approach would be to dredge at a 2:1 (horizontal:vertical) slope to maximize COC removal and place residual cover to a final slope of 3:1 (horizontal:vertical) to allow stable conditions for the cover material following construction. The drawings package (provided under separate cover) includes a typical detail to illustrate the dredge slope in combination with the residual cover slope.

Shoreline Stability / Setbacks

Another geotechnical consideration was shoreline stability, particularly for shorelines and existing structures and bulkheads adjacent to the dredge areas. The approach was to apply setbacks that provide a reasonable level of shoreline stability assurance based on documented existing shoreline conditions, sediment material and in-situ density, slope stability modeling in critical areas, and previous sediment and dredging engineering experience. The setbacks also are assumed to be acceptable to the owners of shoreline structures as they avoid creating shoreline instability as a result of dredging activities. This assumption will be verified by USACE as part of the access agreement process with the property owners.

An evaluation was performed by USACE in January 2015 (Appendix L to the FFS; Arcadis 2015) that concluded several structures and embankments would not require any additional considerations due to limited dredging depths, while those that would require further considerations likely would require setbacks to the dredging. Shoring or other means of protection were not evaluated during design due to prohibitive costs and/or long-term concerns regarding adjacent property owners. The available data, including shoreline reconnaissance, photographs, hand-drawn cross sections, and narrative descriptions of conditions, were reviewed along with the current DMU boundaries and depths to determine what stability considerations were necessary at each location.

In all DMUs adjacent to the shoreline, a minimum (10-foot) setback with a 2:1 (horizontal:vertical) slope is specified to provide safe dredging conditions. Saturated sediment within the top 4 feet can slough without causing a stability concern for sediment behind it. This is based on the angle of repose of the saturated sediment (Das 1997). Deeper than 4 feet, sediment sloughing sediment could cause undermining or stability concerns for adjacent structures. As such, an assessment was conducted for areas along the shoreline with dredge depths over 4 feet. Areas with dredge depths less than 4 feet were not evaluated as the conditions do not pose a stability concern based on the stability of deeper cuts and common engineering practices. Five critical areas were identified for further evaluation based on shoreline structure stability concerns (i.e., Lake Superior Fishing Co. building, deteriorating wooden revetment walls, and steel sheet pile walls). The five areas consisted of three cross sections identified in the Hughitt

Slip, one typical section in Cummings Slip, and an area near the Dry Docks adjacent to the deepest dredge depth. The evaluations included a comparative approach between the FOS of the existing conditions compared to the FOS for 2:1 and 3:1 dredge slopes using the GeoStudio program Slope/W

(Geo-Slope International Ltd 2012). The resulting FOS indicate that a 2:1 slope with a 10 feet setback for the Cummings Slip, Dry Docks, and the northern end of Hughitt Slip will maintain stability of the shoreline structures. For the remainder of Hughitt Slip, it was determined a 3:1 slope with a 10 feet setback will be used to maintain stability of the shoreline structures including the Lake Superior Fishing Co. building on the west side of the slip and a deteriorating wooden revetment wall assumed to be surrounding the slip shoreline (Appendix L to the FFS; Arcadis 2015). The calculation package identifying specific sections evaluated and associated FOS can be found in Appendix C.

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 14

All scenarios were evaluated by a geotechnical engineer analyzing site conditions, dredging depths, and conditions at each DMU boundary based on professional judgement and experience, shoreline reconnaissance data, and sediment materials geotechnical parameters and typical behaviors under saturated/river conditions. These calculations were performed using the 65% design for these critical areas; however, changes to the design since this point do not warrant updates to this geotechnical evaluation and the results are still applicable. Additional analysis by a geotechnical engineer should be performed prior to additional work for areas where redredging based on confirmation sampling is proposed.

Once the geotechnical evaluation and associated slope modeling were complete, the recommended adjustments were applied to the dredge prism. The grades were reviewed again for constructability to produce the final dredge prism.

2.4 Access and Permits

USACE will coordinate obtaining access for areas intended to be used for support or that will be impacted by RA activities. It is currently assumed that access agreements will be granted for all dredge and support areas as required to perform the work. Access to the work areas will be restricted to construction-related vehicles and personnel unless otherwise negotiated with individual property owners and/or interested parties. Notifications of construction activities will be submitted to property owners prior to construction by

USACE.

Note that approximately one-third of the Cummings Avenue Slip is owned by the State of Wisconsin and leased to Fraser under the terms of a submerged land lease (No author 2010). The extent of the land-lease is provided in the drawings package (provided under separate cover). Any specific considerations or requirements for working within this portion of the site will be determined by USACE in coordination with WDNR and Fraser.

USACE and the Partners will also work with the property owner in Hughitt Slip (property currently for sale) regarding moving the docks to accommodate dredging. It is assumed that the docks will be moved such that dredging can occur per the design.

A summary of the permits required for the project is provided in Table 6. It is anticipated that Arcadis will complete the required permit applications with assistance from the Partners. Completed permits and applications for pending permits may be provided to potential Contractors during the bidding process. The selected Contractor will be required to follow the terms of all access agreements and permits.

Table 6. Summary of Required Permits

Entity Permit

City of Superior Erosion Control Permit – Fraser

Site

City of Superior Erosion Control Permit –

Wisconsin Point Landfill

USACE Section 10/404

G:\Project Docs\Div20\lryfun - 11222\LAR20\Howard Bay\0072011222_DDR Text.docx 15

Entity Permit

WDNR Public Waters Permit

WDNR 401 Water Quality Permit

WDNR

Notice of Intent (NOI) for Land

Disturbing Activity

WDNR Landfill Plan Modification

WDNR Air Pollution Controls2

Additional coordination will also be required with Arcadis/Partners and the City of Superior for the wastewater discharge and Wisconsin Point Landfill Plan modification. The selected Contractor will be required to follow any actions or procedures resulting from these coordination efforts.

2.5 Mobilization and Site Preparation

2.5.1 Mobilization

Once access agreements are secured,…