Stantec Report on Riverside Park

REMEDIAL INVESTIGATION REPORT/CONCEPTUAL SITE MODEL

Former Station A Manufactured Gas Plant

DTE Gas Company

Detroit, Michigan

Prepared for:

DTE Gas Company

One Energy Plaza Drive, Suite 655 GO

Detroit, Michigan 48226

Prepared by:

Stantec Consulting Services Inc.

27280 Haggerty Road, Suite C-11

Farmington Hills, MI 48331

January 20, 2015

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TABLE OF CONTENTS

1.0 INTRODUCTION ................................................................................................................ 1

2.0 SITE HISTORY AND POTENTIAL CONTAMINANT SOURCE AREAS .................................... 3

2.1 Site History .................................................................................................................... 3

2.2 Potential Contaminant Source Areas ...................................................................... 4

2.3 1984 Response Actions .............................................................................................. 6




3.0 2014 REMEDIAL INVESTIGATION WORK SCOPE .............................................................. 9

3.1 Soil Boring Installation ................................................................................................. 9

3.2 Monitoring Well Installation ..................................................................................... 10

3.3 River Gauges ............................................................................................................. 11

3.4 Groundwater Gauging and Sampling .................................................................. 12

3.5 Flux Chamber Sampling .......................................................................................... 12

4.0 SITE DESCRIPTION ........................................................................................................... 14

4.1 Site Setting ................................................................................................................. 14

4.2 Geology/Hydrogeology .......................................................................................... 14

5.0 SUMMARY OF PREVIOUS RESPONSE ACTIONS ............................................................. 16

6.0 COMPLETED INTERIM RESPONSE ACTIONS.................................................................... 18

7.0 SOIL CHARACTERIZATION .............................................................................................. 19

7.1 Oily Substances and Tar-Like Materials ................................................................. 19

7.2 Constituents of Potential Concern in Soil .............................................................. 19

7.3 Part 201 Soil Cleanup Criteria ................................................................................. 19

7.4 Evaluation of Copcs in Soil ...................................................................................... 20

7.4.1 1984 Soil Data .......................................................................................................... 20

7.4.2 2011 Soil Data .......................................................................................................... 21

7.4.3 2012 Soil Data .......................................................................................................... 21

7.4.4 2014 Soil Data .......................................................................................................... 21

8.0 GROUNDWATER CHARACTERIZATION .......................................................................... 22

8.1 Non-Aqueous Phase Liquids ................................................................................... 22

8.2 COPCs in Groundwater ........................................................................................... 22

8.3 Part 201 Groundwater Cleanup Criteria ............................................................... 22

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TABLE OF CONTENTS (Cont.)

8.4 Evaluation of COPCs in Groundwater ................................................................... 23

9.0 SOIL GAS CHARACTERIZATION ..................................................................................... 24

9.1 COPCs in Soil Gas ..................................................................................................... 24

9.2 Part 201 Soil Gas Screening Criteria ....................................................................... 24

9.3 Evaluation of COPCs in Soil Gas ............................................................................. 24

10.0 AMBIENT AIR CHARACTERIZATION................................................................................ 26

11.0 ENVIRONMENTAL RECEPTORS AND PATHWAYS ........................................................... 27 11.1 Drinking Water Pathway ........................................................................................ 27

11.2 Volatilization of COPCs in Soil and Groundwater to Indoor Air ........................ 28

11.3 Volatilization of COPCs in Soil to Ambient Air ..................................................... 28

11.3.1 Parcel 1 .................................................................................................................... 28

11.3.2 Parcel 2 .................................................................................................................... 29

11.3.3 Parcel 2A ................................................................................................................. 29

11.4 Direct Contact with COPCs in Soil ........................................................................ 29

11.4.1 Parcel 1 .................................................................................................................... 29

11.4.2 Parcel 2 .................................................................................................................... 29

11.4.3 Parcel 2A ................................................................................................................. 30

11.5 Groundwater/Surface Water Interface Pathway .............................................. 30

12.0 CONCLUSIONS ............................................................................................................... 31

13.0 DATA GAPS .................................................................................................................... 33

14.0 ADDITIONAL FUTURE RESPONSE ACTIONS .................................................................... 34

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TABLE OF CONTENTS (Cont.)

LIST OF FIGURES

1. Site Location Map

2. Site Parcel Map

3. Site Map

4. Site and Surrounding Properties Map

5. Residual Contaminant Source Materials and Soil Exceeding Part 201 Criteria 1984

- 2012 Soil Samples Map

6. Residual Contaminant Source Materials and Soil Exceeding Part 201 Criteria 2014

Soil Samples Map

7. Groundwater Analytical Results May 29, 2014 - June 2, 2014 8. Groundwater Contour Map May 29, 2014 9. Geologic Cross Section Location Map

10. Geologic Cross Sections - A-A through C-C 11. Soil Gas Analytical Results September 24, 2012

LIST OF TABLES

1. 1984 Soil Analytical Results Detectable VOCs and Base/Neutrals 2. 1984 Soil Analytical Results Metals 3. 2011 Soil Analytical Results

4. 2012 Soil Analytical Results VOCs, PAHs, Phenols, Available Cyanide and pH 5. 2012 Soil Analytical Results - Metals

6. 2012 Soil Gas Analytical Results

7. 2014 Soil Analytical Results VOCs, PAHs, Available Cyanide, Ammonia and pH 8. 2014 Soil Analytical Results Metals 9. 2014 Soil Analytical Results Phenols 10. 2014 Groundwater Analytical Results VOCs, PAHs, Metals, Cyanide and

Ammonia

11. 2014 Groundwater Analytical Results Phenols 12. Groundwater Elevation Data

LIST OF APPENDICES

A. Parcel 1 Aerial Photographs

B. Boring Logs

C. Map of PVC Membrane

D. Laboratory Analytical Reports 2014 Soil Data E. Laboratory Analytical Reports 2014 Groundwater Data F. Ambient Air Assessment Report

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1.0 INTRODUCTION

Stantec Consulting Corporation (Stantec), on behalf of DTE Gas Company (DTE Gas), a

subsidiary of DTE Energy, has prepared this Remedial Investigation Report/Conceptual

Site Model (Report) for the former Station A manufactured gas plant (MGP) located at

3085 West Jefferson in Detroit, Michigan (the Site). Refer to the Site Location Map

(Figure 1) for detailed information on the location of the Site. The Site is no longer

owned by DTE Gas and currently consists of portions of the City of Detroits Riverside

Park along with land owned by the Norfolk Southern Corporation (NSC).

The Site consists of approximately 10 acres of land and is located adjacent to the

Ambassador Bridge with the Detroit River bordering the Site to the southeast. Riverside

Park consists of three parcels. Parcels 1 and 2 are shown on Figure 2 and were part of

the former Station A manufactured gas plant. Parcel 3 was not historically owned or

used by DTE Gas and is not included in this Report. Based on available information, the

approximate locations of the former MGP components have been overlaid onto the

existing Site Map (Figure 3). Refer to the Site Map (Figure 3) and Site and Surrounding

Properties Map (Figure 4) for Site and surrounding area features including the

approximate locations of the former MGP structures. Soil borings and monitoring wells

have been installed on the Site. Soil and groundwater samples have been collected to

investigate potential subsurface impacts related to historical MGP activities at the Site.

Concentrations of volatile organic compounds (VOCs), polynuclear aromatic

hydrocarbons (PAHs) and inorganics have been detected in soil and groundwater

samples above Part 201 of Public Act 451 of 1994, as amended (Part 201) cleanup

criteria.

The October, 30, 2013 Response Activity Plan (ResAP) prepared by Stantec and

approved by the Michigan Department of Environmental Quality (MDEQ) on

December 5, 2013 was implemented in January through June 2014. An additional work

plan was developed through email correspondence between the Michigan

Department of Environmental Quality (MDEQ), DTE Gas and Stantec to collect ambient

air samples using flux chambers on Parcel 1. The work scope and flux chamber

sampling locations were approved in a November 15, 2013 email from the MDEQ to the

DTE Gas and Stantec. The flux chamber sampling work plan was implemented in

September 2014. The activities completed during implementation of the ResAP and

flux chamber sampling are discussed in Section 3.0.

This Report has been prepared to include the information present in a Conceptual Site

Model (CSM). This Report was prepared to identify the current conditions using historical

and current data for the Site and surrounding area. This information presented in the

Report generally follows the Standard Guide for Developing Conceptual Site Models for

Contaminated Sites (ASTM E1689-95 (Reapproved 2008)). The objectives of the Report

were the following:

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To integrate technical information from various sources;

To evaluate potential risks to human health and the environment; and,

To identify data needs and data collection activities.

The Report includes:

A description of background and operational history of the Site;

A summary of the Sites environmental setting;

A chronology of Site characterization activities and interim response actions;

A summary of completed interim response actions;

A description of the nature and extent of impacts in soil and groundwater;

An evaluation of migration pathways; and,

An evaluation of environmental receptors.

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2.0 SITE HISTORY AND POTENTIAL CONTAMINANT SOURCE AREAS

2.1 Site History

A summary of the history of the Site was derived from historical maps provided by DTE

Gas, historical photographs and previous environmental reports. The significant

historical operations and features of the Site and adjacent properties are summarized in

this section.

The former Station A MGP was constructed by the Detroit Gas and Light Company in

1867 and was operated by the Detroit Gas and Light Company, Detroit City Gas

Company and Michigan Consolidated Gas Company (MichCon) until 1954 at which

time natural gas pipelines became established. Please note that MichCon changed its

legal name to DTE Gas Company (DTE Gas), a subsidiary of DTE Energy, in 2013.

The MGP primarily generated coal gas and water gas to supply the city of Detroit prior

to the availability of natural gas. The coal gas manufacturing process consisted of

heating bituminous coal in retorts. The water gas manufacturing process generally was

similar to the coal gas process but also injected steam to produce gas. Coke

generated during the gas production was either returned to the ovens for further

processing or sold locally. Impurities in the gas were removed before delivery to the

customer. The byproducts typically associated with MGP processes included tar, pitch,

hydrogen cyanide, hydrogen sulfide, and various liquids. Many of these impurities were

useful products that could be sold.

Based on readily available historical drawings and maps, the following non-DTE Gas

operations were also previously present on Parcels 1, 2 or 2A:

Tar Distillation Operation;

Railroad;

Pintsch Gas Plant;

Toluene recovery operation;

Detroit International Bridge Company; and,

Boat slip.

Parcel 2A of the former MGP site was sold to Wabash Railroad Company (predecessor

of NSC) in 1969 and has continued to be used for railroad related usage. Parcels 1 and

2 of the former MGP site were sold to the City of Detroit in 1979 and were developed

into an extension to the Riverside Park. Parcel 1 currently consists of a baseball diamond

infield, two small bleacher sections and a fenced backstop. The remainder of Parcel 1

consists predominantly of grassy areas. There are no play structures, picnic areas or

other recreational features on Parcel 1. Parcel 2 consists of an asphalt parking lot,

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grassy areas and picnic pavilion adjacent to the Detroit River. The City of Detroit is the

owner of Parcels 1 and 2. Railroad tracks and property owned by NSC (Parcel 2A)

separates Parcels 1 and 2. According to the City of Detroit Recreation Department,

Riverside Park is currently closed and will remain closed until environmental remediation

is completed.

2.2 Potential Contaminant Source Areas

The primary potential contaminant source areas on the Site are former MGP operations,

tar distillation operations, toluene recovery operations, and pintsch gas plant

operations.

MGP Operations

The MGP structures indicated on historical and Sanborn maps included the following as

shown on Figure 3:

Two (2) relief gas holders;

Condenser and scrubber;

Purifiers;

Water Gas Tar, Oil Water, and Oil Tar Separators;

Retorts;

Tar Tanks and Gas/Oil Storage Tanks;

Ammonia well and tank;

Oil and Tar Wells; and,

Other Various Buildings.

During the generation of manufactured gas, byproducts from two primary processes

often resulted in impacts to the environment: gas production and gas clean-up. During

gas production, the coal gas and water gas processes generated residual

hydrocarbons. According to Management of Manufactured Gas Plant Sites (Hayes

and others; 1996, Amherst Scientific Publishers, Amherst, Massachusetts), the

hydrocarbon residuals associated with the coal gas process consisted primarily of coke

and hydrocarbons (tars, oils and lampblack). The gas cleanup phase generally

consisted of scrubbing the gases to remove naphthalene, ammonia, cyanide and light

oils.

Tar Distillation Operations

Historical documentation indicated that tar distillation operations occurred on the Site

from the early 1900s to the 1920s. The tar distillation company was a distiller of coal tar

products and a manufacturer of roofing and paving materials including:

Pitch (for paving, roofing and waterproofing);

Felt (for building, roofing and slater);

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Asphalt; and,

Tarvia (a surfacing and binding material for roads and drives).

As indicated on Figure 3, tar distillation operations occurred at the western portion of

Parcel 2. Former structures associated with tar distillation operations included tar tanks,

storage tanks, condensers, stills and boiler and coolers. Potential residual contaminants

associated with a tar distillation operation include various hydrocarbons (including tars).

Toluene Recovery Operations

Historical documentation shows that a toluol recovery plant was built and operated to

generate toluene from the coal and water gas from approximately 1917 to 1919. The

toluene was a critical war material used for the primary purpose of manufacturing

trinitrotoluene (TNT). As indicated on Figure 3, toluene recovery operated within Parcel

1. Former structures associated with the toluene recovery operations included toluol

tanks, toluol pipe trench, toluol loading pipe trench, and a toluol machinery building.

Toluene would be the primary potential residual contaminant associated with a toluol

recovery plant.

Pintsch Gas Plant Operations

Historical documentation indicated that a Pintsch Gas Plant operated at the Site from

the 1890s to the 1930s. Pintsch plants were typically operated by railroad companies

and these plants produced compressed illuminating gas for use in passenger rail cars.

As indicated on Figure 3, former structures associated with a Pintsch Gas Plant included

a gas plant, tar holders, gas holders and storage tanks. These former structures are

noted on Parcels 1 and 2A (Figure 3). Types of wastes that would result from a Pintsch

gas operation could include hydrocarbons released during production, ash from coal

and coke incineration and wastes derived as a result of tar management and gas

purification.

Other Potential Sources

During the 2014 investigation activities, contractors working for the Detroit International

Bridge Company (DIBC) were observed to be installing large diameter utilities along the

eastern portion of the Site without City of Detroit permission. Barren soil and soil piles

were observed on Parcel 1 along the entire eastern boundary. This information and

concern over the potential for exacerbation of potential subsurface impacts were

communicated to the City of Detroit and the MDEQ. This potential exacerbation is a

potential contaminant source area. Aerial photographs of the site disruption are

included as Appendix A.

Also, historical documentation indicated that various activities may have occurred on

the Site that may have exacerbated or contributed potential contaminants. Some of

these activities include: Placement of fill materials to expand shoreline, railroad

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operations, Steamship S.S. Montrose salvage activities, storm sewer installation by

Wayne County Road Commission, and various other historical adjacent operations.

2.3 1984 Response Actions

In 1984 a site investigation of Parcels 1 and 2 was conducted by EDI Engineering &

Science (EDI) on behalf of DTE Gas. The work scope and results of this investigation are

presented in Site Investigation Former Coal Gas Manufacturing Plant Station A (EDI;

October 1984).

Twenty-nine soil borings were advanced and four surface soil samples were collected

on Parcels 1 and 2 in 1984. The soil borings are identified on Figure 3 as S-1 through S-16,

S-19 through S-28 and S-30 through S-32. The four surface soil sample locations are

designated on Figure 3 as SS-1, SS-2, SS-3 and SS-9. Soil samples were collected from

selected soil borings for laboratory analysis of volatile organic compounds (VOCs),

base/neutrals, total cyanide (wet weight), total phenols (wet weight) and metals. The

VOCs, base/neutrals and metals analytical results of the 1984 soil samples are

presented in Tables 1 and 2. These tables contain the MDEQ Part 201 nonresidential soil

cleanup criteria for comparison purposes.

Six monitoring wells (W-1 through W-6 on Figure 3) were installed on Parcels 1 and 2 to

determine groundwater flow direction and collect groundwater samples for laboratory

analysis. Because the sampling methodologies are not known, the 1984 groundwater

data are not presented in this Report. In 2012, these monitoring wells were not

observed on Parcels 1 and 2.

Six subsurface air wells were installed and these air wells are identified as A-1 through A-

6 on Figure 3. According to EDI October 1984, these air wells were installed to depths

ranging from five to ten feet below the surface (bs). In 2012, these air wells were not

observed on Parcels 1 and 2.

Drilling logs for the 1984 soil borings, monitoring wells and air wells are presented in

Appendix B. The depths of the soil borings advanced in 1984 ranged from three feet to

30 feet below the surface. The information presented on these drilling logs indicate that

contaminant source materials from former MGP operations and/or other former

operations on Parcels 1 and 2 were encountered in the subsurface. The 1984 boring

locations where potential contaminant source materials are indicated are presented

on Figure 5. Figure 5 also presents the 1984 soil samples that exceeded the Part 201

screening criteria.


The results of the 1984 site assessment indicated that shallow soils (generally upper

twelve inches) within a portion of Parcel 2 were stained blue as a result of ferric

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ferrocyanide being present within these soils. The results of the investigation of the blue-

stained soils are presented in Additional Investigation, Investigation of Blue Staining of

Surface Grasses, Riverside Park, Station A (EDI; March 1985). To prevent potential direct

contact exposures, a blue PVC membrane overlain by approximately one to two and a

half feet of clean granular material, topsoil and grass was emplaced over parts of the

grassy areas within Parcel 2. A map showing the extent of the PVC membrane/barrier is

presented in Appendix C. In 2012 and 2014, the presence of the blue PVC membrane

was confirmed. The components of the 1985 response actions are presented in

Remedial Action Plan (EDI; October 1985).


In October 2011, a subsurface investigation was conducted by TEI Environmental

Solutions (TEI) on behalf of the City of Detroit Recreation Department. The results of this

subsurface investigation are presented in Phase II Subsurface Investigation Riverside

Park (TEI; January 17, 2012). Six soil borings were advanced on Parcels 1 and 2. These

six borings are referred to as SP-1 through SP-6 on Figure 3. Three of the soil borings (SP-

1, SP-2 and SP-3) were advanced on Parcel 1 and the three remaining soil borings (SP-4,

SP-5 and SP-6) were advanced on Parcel 2. During the advancement of these six soil

borings, soil samples were collected for laboratory analysis of VOCs, semi-volatile

organic compounds and metals. The October 2011 soil analytical results are presented

in Table 3. The boring locations where contaminant source materials are indicated are

presented on Figure 5. Figure 5 also presents the 2011 soil samples that exceeded the

Part 201 screening criteria.

Temporary monitoring wells were installed in borings SP-2, SP-3 and SP-6 and

groundwater samples were collected for laboratory analysis from these temporary

monitoring wells. Temporary monitoring wells were not installed in borings SP-1, SP-4 and

SP-5 because groundwater was not encountered during the advancement of theses

borings. The construction details of the temporary monitoring wells are not known. The

MDEQ generally requires that monitoring wells be allowed to stabilize for at least 72

hours before groundwater samples are collected. Because the construction details of

the temporary monitoring wells are unknown and the groundwater samples were

collected on the same day the boring was advanced, the October 2011 groundwater

data are not presented in this Report.

Drilling logs for the 2011 soil borings are presented in Appendix B. The depths of the

October 2011 soil borings ranged from 15 feet to 20 feet below the surface.


In September and November 2012, a subsurface investigation consisting of soil and soil

gas sampling on Parcels 1 and 2 was completed by Stantec, on behalf of DTE Gas. The

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results of this investigation are presented in Response Activity Plan (Stantec; October 30,

2013) This investigation consisted of the advancement of 54 shallow soil borings (33 on

Parcel 1 and 21 on Parcel 2) and the installation of 15 soil vapor points in 15 of the soil

borings. On Figure 3, these borings are designated as:

SB-1 through SB-5;

SB-10, SB-11 and SB-11A;

SB-14 through SB-39;

SB-41 and SB-43 through SB-46;

VP-1 through VP-10; and,

VP-12 through VP-16.

The depths of the borings ranged from one foot to 6.5 feet bs.

During the advancement of the soil borings, soil samples were collected for laboratory

analysis of selected VOCs, polynuclear aromatic hydrocarbons (PAHs), metals, phenols,

available cyanide and pH. The soil analytical results are presented in Tables 4 and 5.

Soil gas samples were collected from the soil vapor points for laboratory analysis of

selected VOCs, naphthalene, 2-methylnaphthalene and mercury. The soil gas data are

presented in Table 6.

The soil and soil gas data for Parcels 1 and 2 were presented to the MDEQ and the City

of Detroit during meetings conducted in early 2013. The results of the soil and soil gas

data from Parcel 1 were presented in Response Activity Plan Parcel 1 (Stantec;

February 20, 2013).

Drilling logs for the 2012 soil borings are presented in Appendix B. The information

presented on these drilling logs indicate that contaminant source materials from former

MGP operations and/or other operations formerly present on Parcels 1 and 2 were

encountered in the subsurface. The 2012 boring locations where contaminant source

materials are indicated are presented on Figure 5. Figure 5 also presents the 2012 soil

samples that exceeded the Part 201 screening criteria.

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3.0 2014 REMEDIAL INVESTIGATION WORK SCOPE

A proposed work scope for a subsurface investigation consisting of soil sampling,

monitoring well installation and groundwater sampling on Parcels 1, 2 and 2A was

outlined in the ResAP prepared and submitted by Stantec on October 30, 2013 and

approved by the MDEQ in December 2013. In January through July 2014, the work

outlined in the ResAP was completed by Stantec, on behalf of DTE Gas. Additionally, in

order to evaluate the Ambient Air Volatile Source Inhalation pathway, a work plan was

developed through email correspondence between the MDEQ, DTE Gas and Stantec

to collect flux chamber samples on Parcel 1. The work scope and flux chamber

sampling locations were approved in a November 15, 2013 email from the MDEQ to DTE

Gas and Stantec. Stantec, on behalf of DTE Gas, completed the flux chamber

sampling on September 18, 2014. The timing of the flux chamber sampling was delayed

because the sampling criteria (as outlined in the MDEQs Guidance Document for the

Vapor Intrusion Pathway dated May 2013) could not be met due to weather

conditions and delayed the sampling. A summary of the work completed in 2014 is

provided below.

3.1 Soil Boring Installation

The ResAP proposed the advancement of fifty-eight soil borings with fifteen of the soil

borings being converted to monitoring wells. Prior to beginning the soil boring

installation activities, a MISS DIG utility locate meeting was conducted to determine the

accessibility of each proposed boring location. During this meeting, numerous utility

manholes were observed along the east side of Parcel 1. The origin of the utility

manholes and the associated underground utilities were not known to the City of

Detroit or the attendees at the MISS DIG utility locate meeting. Based on available

information, it appears that the unknown utilities were installed by the DIBC.

Additionally, a storm sewer and electric line were identified on maps obtained from the

Michigan Department of Transportation (MDOT) as being connected to the pump

house southwest of Parcel 2. Based on the presence of these utilities, proposed borings

A1 and E1 and proposed monitoring wells AA1, EE1, Q1 and P1 were not installed due

to utility concerns. Soil borings SB-105-14, SB-106-14 and SB-107-14 were advanced to

replace proposed borings Q1, EE1 and P1, respectively. Additionally, SB-96-14 through

SB-101-14 were advanced to investigate oily substances and/or tar-like materials

observed in soil borings installed during the 2014 investigation.

Based on these changes to the ResAP, the 2014 investigation consisted of the

advancement of 61 soil borings (33 on Parcel 1, 26 on Parcel 2 and 2 on Parcel 2A). On

Figure 3, these borings are designated as SB-47-14 through SB-107-14. A prefix of P1, P2

or P2A was added to each boring name to identify the Parcel where the boring was

installed. The borings that were installed on each parcel are:

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Parcel 1

P1SB-47-14 through P1SB-68-14;

P1SB-94-14 through P1SB-98-14; and,

P1SB-102-14 through P1SB-107-14.

Parcel 2

P2SB-69-14 through P2SB-86-14;

P2SB-89-14 through P2SB-93-14; and,

P2SB-99-14 through P2SB-101-14.

Parcel 2A

P2ASB-87-14 and P2ASB-88-14.

The depths of the borings ranged from 4 feet (auger refusal) to 36 feet bs.

During the advancement of the soil borings, soil samples were collected from select

boring locations as outlined in the October 2013 ResAP. The soil samples were

submitted for laboratory analysis of selected VOCs, PAHs, metals, phenols, available

cyanide, ammonia and pH. The soil analytical results are presented in Tables 7 through

9. Figure 6 presents the 2014 soil samples that exceeded the Part 201 screening criteria.

Laboratory analytical reports from the 2014 soil sampling are included as Appendix D.

The following Quality Assurance/Quality Control (QA/QC) samples were collected

during the soil boring installation:

Duplicate soil samples (4) results shown on Tables 7 through 9;

Matrix Spike/Matrix Spike Duplicate samples (4);

Equipment Blanks (2);

Field Blanks (4); and,

Trip Blanks (5).

Drilling logs for the 2014 soil borings are presented in Appendix B. The information

presented on these drilling logs indicate that contaminant source materials from historic

operations formerly present on Parcels 1, 2 and 2A were encountered in the subsurface.

A highly plastic clay unit was observed at depths ranging from 26 to 36 feet bs. Visual

impacts were not noted within this clay unit. The 2014 boring locations where

contaminant source materials are indicated are presented on Figure 6.

3.2 Monitoring Well Installation

The Work Plan proposed the installation of fifteen monitoring wells. Groundwater was

not encountered at all of the soil borings at the Site. Therefore, monitoring wells were

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only installed at locations where a groundwater unit was observed. Based on these

observations, eleven monitoring wells were installed at the Site. The monitoring well

locations are shown on Figure 3. The wells that were installed on each parcel are:

Parcel 1

P1SB-65-14/MW-1;

P1SB-64-14/MW-2;

P1SB-59-14/MW-3;

P1SB-68-14/MW-4; and,

P1SB-105-11/MW-11

Parcel 2

P2SB-89-14/MW-5;

P2SB-81-14/MW-6;

P2SB-93-14/MW-7;

P2SB-92-14/MW-8;

P2SB-91-14/MW-9; and,

P2SB-90-14-/MW-10

Monitoring wells were not installed at the P1SB-94-14, P1SB-106-14 and P1SB-107-14

locations as groundwater was not observed at these locations. A monitoring well was

not installed at the proposed AA1 location (see Figure 3) due to utilities. A replacement

well was not proposed for this location due to the proximity of P1SB-65-14/MW-1.

Drilling/Well Construction logs for these monitoring wells are presented in Appendix B.

Following installation of the monitoring wells, the wells were developed by

pumping/surging until the pumped water was relatively free of particulate matter or the

well went dry at least three times. The top-of-casing elevation was then surveyed. From

top-of-casing elevations and depth to groundwater measurements, groundwater

elevations were determined.

3.3 River Gauges

It was stated in the Email Response to Notice of Approval of Response Activity Plan

Letter (DTE Gas email to the MDEQ dated December 5, 2013) that DTE will plan to

utilize stilling wells to monitor the river levels as suggested and will consider instrumenting

the stilling wells with data loggers when routine monitoring is implemented. Stilling well

installation was not completed during the soil boring/monitoring well installation phase

of the investigation as ice was still prevalent on the Detroit River and significant

anchoring to the seawall would need to be completed. Therefore, in order to establish

the elevation of the Detroit River during the groundwater sampling event, two river

gauges (RG-1 and RG-2 shown on Figure 3) were established at the top of the seawall

in Parcel 2. The river gauge elevations were surveyed relative to site elevation

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benchmarks. If necessary, a methodology for installing the stilling wells can be discussed

with the MDEQ and provided to the City of Detroit for review and approval prior to

installing stilling wells.

3.4 Groundwater Gauging and Sampling

Depth to groundwater gauging data and groundwater samples were collected from

site monitoring wells on May 29 through June 2, 2014. A second groundwater gauging

event was completed on July 7, 2014. During the May 29, 2014 groundwater gauging

event, non-aqueous phase liquid (NAPL) was identified at the bottom of monitoring

wells MW-1, MW-3 and MW-5. Therefore, groundwater samples were not collected from

these monitoring wells.

Groundwater samples were submitted for laboratory analysis of selected VOCs, PAHs,

metals, phenols, available cyanide, ammonia and pH. The groundwater analytical

results are presented on Tables 10 and 11 and Figure 7. Groundwater elevation data

are presented in Table 12 and a groundwater contour map is included as Figure 8.

Laboratory analytical reports from the 2014 groundwater sampling are included as

Appendix E.

The following QA/QC samples were collected during the groundwater sampling event:

Duplicate groundwater samples (1) results shown on Tables 10 and 11;

Matrix Spike/Matrix Spike Duplicate samples (1); and,

Field Blanks (1).

An equipment blank was not collected as detailed in the ResAP as dedicated

downhole sample tubing was utilized for each individual monitoring well.

3.5 Flux Chamber Sampling

To further evaluate the potential ambient air risks from subsurface MGP residual

materials at and around the VP-3 area, the isolation flux chamber method (dynamic-

chamber method) was used to directly measure contaminant concentration at the soil-

air interface. A sampling plan to collect ambient air samples using flux chambers was

prepared and submitted to the MDEQ as part of a November 13, 2013 electronic

message from Stantec. In their November 15, 2013 electronic message to Stantec, the

MDEQ approved of the flux chamber sampling plan. The flux chamber samples were

collected on September 18, 2014. As noted above, the flux chamber sampling would

have occurred sooner, however, sampling criteria (as outlined in the MDEQs

Guidance Document for the Vapor Intrusion Pathway dated May 2013) could not be

met due to weather conditions and delayed the sampling.

13

On September 18, 2014, flux chamber samples were collected within a 100 foot radius

of VP-3 at the nine locations at and around VP-3 (Figure 3). On this figure, the flux

chamber sample locations are identified as P1FC-01-14 through P1FC-09-14. Flux

chamber samples were collected three times on September 18, 2014 at each sample

location. The work scope, sampling procedures and results of the sampling activities are

presented in Appendix F.

14

4.0 SITE DESCRIPTION

4.1 Site Setting

The Site is located in Section 24 of Township 2 South, Range 11 East (T2S R11E) of Wayne

County at 3085 West Jefferson Avenue in the City of Detroit, Michigan (Figure 1). The

Site is located adjacent to the Detroit River and Ambassador Bridge and consists of

approximately 10 acres of land. DTE Gas currently does not own any portions of the

Site.

The Site currently consists of portions of the City of Detroits Riverside Park (i.e., Parcel 1,

and 2) along with land owned by the NSC (Parcel 2A) (Figure 2). The Site is bounded by

Jefferson Avenue to the north, the Ambassador Bridge to the east, and the Detroit River

to the south. Railroad tracks are situated between Parcel 2A and Parcel 1 and are

reportedly used by various railroad companies. A vacant lot is situated west of

Riverside Park Parcel 1. Vehicles were observed parked in this lot during a portion of the

remedial investigation. A boat slip/launch is situated west of Riverside Park Parcel 2.

The surrounding properties are primarily commercial/industrial with the nearest

residential property located approximately 1,300 feet to the west of the Site (Figure 4).

On-Site groundwater is not being used as a drinking water source. The City of Detroit

receives its water supply from the Great Lakes System. According to the Detroit Water

and Sewerage Department (DWSD) website, the system uses fresh water from three

intakes. Two intakes are located in the Detroit River approximately 8 miles north and 14

miles south of the Site.

4.2 Geology/Hydrogeology

According to historical drilling logs for borings advanced within Township 2 South,

Range 11 East, the geology of the Site area consists of Pleistocene age glacial drift

underlain by Devonian age Dundee Limestone. The glacial drift ranges in thickness

from 73 feet to 114 feet and consists predominately of clay.

The discussion of the geology and hydrogeology of Parcels 1, 2 and 2A is based on the

evaluation of boring logs and soil descriptions presented in Appendix B.

The geology of Parcels 1, 2 and 2A consists of fill materials overlying native clay. The

thickness of the fill materials overlying the native clay ranges from approximately 8 feet

to 24 feet bg.

The fill materials above the native clay generally consist of the following:

15

Silty sand, clay and silt with concrete;

Wood debris, slag, coal, brick and concrete; and,

Dry, stiff clay (most likely a clay cap in some areas).

Residual contaminant source materials were encountered in some of the borings. As

indicated by the information in the boring logs, clay is generally present above residual

contaminant source materials. It appears likely that when the former MGP structures

and other structures were dismantled, a clay cap was placed over the contaminant

source materials.

Beneath the fill material is a brown clay unit that is present at depths ranging from 8 to

32 feet bs. Below the brown clay unit is a gray high plasticity clay unit that was

observed at depths ranging from 26 to 36 feet bs. Soil impacts were not observed within

this deeper clay unit.

The soil types and fill materials described above are presented on geologic cross

sections presented on Figures 9 and 10.

Groundwater beneath the Site was encountered intermittently within the fill materials.

Based on groundwater elevation data collected from site monitoring wells on May 29,

2014, the depth to groundwater is approximately 7 to 10 feet below the surface. The

ResAP proposed monitoring wells at the P1SB-94-14, P1SB-106-14, P1SB-107-14 and P2SB-

79-14 locations. However, groundwater was not encountered during the installation of

these borings. Therefore, monitoring wells were not installed. Based on the above

information, a continuous groundwater unit was not observed across the Site. It

appears that the groundwater encountered during the investigation does not

constitute a potable aquifer.

The May 29, 2014 groundwater contour map prepared from elevation data recorded in

site monitoring wells (Figure 8) indicates that groundwater flows south towards the

Detroit River.

16

5.0 SUMMARY OF PREVIOUS RESPONSE ACTIONS

The locations of the soil borings and monitoring wells advanced/installed as part of the

remedial investigations conducted on the Site are presented on Figure 3. A

chronological summary of the correspondence with the MDEQ are presented as

follows:

Site Investigation Former Coal Gas Manufacturing Plant Station A (EDI Engineering &

Science (EDI); October 1984);

Additional Investigation, Investigation of Blue Staining of Surface Grasses Riverside

Park, Station A (EDI; March 1985);

Remedial Action Plan (EDI; October 1985);

Phase II Subsurface Investigation (TEI Environmental Solutions (TEI): January 2012);

Meeting with MichCon, City of Detroit, MDEQ and Stantec: (April 2012);

Response Activity Plan (Stantec; July 2012);

Response Activity Plan Comments (MDEQ; August 31, 2012);

Response to MDEQ Comments (Stantec; September 7, 2012);

Response Activity Plan Parcel 1 (Stantec; February 20, 2013);

Riverside Park Closure Notification Letter (City of Detroit; March 27, 2013);

Insufficient Information Letter (MDEQ; July 19, 2013);

Meeting between MDEQ and DTE Gas (October 16, 2013);

Email Correspondence to DTE Gas with Response Activity Plan Comments (MDEQ;

October 16, 2013);

Response Activity Plan Comments Email Response (Stantec; October 30, 2013);

Response Activity Plan (Stantec; October 30, 2013);

Response Activity Plan Air Sampling Comments (MDEQ; November 5, 2013);

Revised Air Sampling Plan (Stantec; November 8, 2013);

Email Approving Revised Air Sampling Plan (MDEQ; November 15, 2013);

Notice of Approval of Response Activity Plan Letter (MDEQ; December 4, 2013);

Email Response to Notice of Approval of Response Activity Plan Letter (DTE Gas;

December 5, 2013);

Notice of Exceedance of Groundwater/Surface Water Interface Criterion Based on

Acute Toxicity Letter (Stantec; June 25, 2014); and,

Meeting between MDEQ, City of Detroit and DTE Gas (November 12, 2014).

A summary of the remedial investigations and interim response actions discussed in the

correspondence above is presented in the following table.

17

Consultant Date of Activity Activity

EDI

Engineering

& Science

(EDI)

1984

Twenty-nine soil borings (S-1 through S-16, S-19 through

S-28 and S-30 through S-32), four surface sample

locations (SS-1, SS-2, SS-3 and SS-9), six monitoring wells

(W-1 through W-6) and six subsurface air wells (A-1

through A-6) were installed. Forty-four soil samples

were submitted for analysis for VOCs, base/neutrals,

total cyanide, total phenols and metals.

EDI 1985

A blue PVC membrane overlain by approximately one

to two and a half feet of clean granular material,

topsoil and grass was placed over blue stained soil to

prevent potential direct contact exposures.

TEI

Environment

al Solutions

(TEI)

2011

Six soil borings (SP-1 through SP-6) and three

temporary monitoring wells (SP-2, SP-3 and SP-6) were

installed. Nine soil samples were submitted for analysis

for VOCs, SVOCs, and metals.

Stantec

Consulting

Services, Inc.

(Stantec)

2012

Thirty-nine shallow soil borings (SB-1 through SB-5, SB-10,

SB-11, SB-11A, SB-14 through SB-39, SB-41, SB-43

through SB-46) and fifteen vapor points (VP-1 through

VP-10 and VP-12 through VP-16) were installed.

Seventy-six soil samples were submitted for analysis for

VOCs, PAHs, metals, phenols, available cyanide and

pH. Fifteen soil gas samples were collected from the

vapor points and submitted for analysis for VOCs,

naphthalene, 2-methylnaphthalene and mercury.

Stantec 2014

Sixty-one soil borings (SB-47-14 through SB-107-14) and

eleven monitoring wells (MW-1 through MW-11) were

installed on the property. Thirty-two soil samples and

eight groundwater samples were submitted for

analysis for VOCs, PAHs, phenols, metals, available

cyanide, ammonia and pH. Flux chamber sampling

was conducted at nine locations (P1FC-01-14 through

P1FC-09-14). Twenty-seven flux chamber samples

(three samples from each flux chamber location)

were submitted for laboratory analysis for BTEX, TMBs,

Naphthalene and 2-methylnaphthalene.

18

6.0 COMPLETED INTERIM RESPONSE ACTIONS

As discussed in the Remedial Action Plan (EDI; October 1985), shallow soils (generally

upper twelve inches) within Parcel 2 were stained blue as a result of former

manufactured gas purification processes which caused ferric ferrocyanide impacts. To

prevent direct contact exposures, a blue PVC membrane overlain by approximately

two to four feet of clean granular material, topsoil and grass was emplaced over parts

of the grassy areas within Parcel 2. Appendix C includes a map of the PVC membrane.

19

7.0 SOIL CHARACTERIZATION

The evaluation of constituents of potential concern (COPCs) in soil consisted of the

following:

Review of boring logs for the presence/absence of oily substances and tar-like

materials; and,

Comparison of soil data generated from vadose zone soil samples to the MDEQs

Part 201 nonresidential soil cleanup criteria.

7.1 Oily Substances and Tar-Like Materials

The presence of oily substances and/or tar-like materials was recorded in the boring

logs during the 1984, 2011, 2012 and 2014 investigations. Refer to Figures 5 and 6 for

locations of the borings indicated these residual contaminant source materials. The

data on Figures 5 and 6 indicate that residual contaminant source materials were

encountered within the former footprints of the MGP and the tar distillation operation.

Refer to Appendix B for copies of borings logs.

7.2 Constituents of Potential Concern in Soil

Soil analytical results for the individual COPCs outlined below and the Part 201

nonresidential cleanup criteria based on the December 30, 2013 MDEQ criteria tables

for these COPCs are presented in the following tables:

Table 1 1984 Soil Analytical Results Detectable VOCs and Base/Neutrals

Table 2 1984 Soil Analytical Results Metals

Table 3 2011 Soil Analytical Results

Table 4 2012 Soil Analytical Results VOCs, PAHs, Phenols, Available Cyanide and

pH

Table 5 - 2012 Soil Analytical Results Metals

Table 7 - 2014 Soil Analytical Results VOCs, PAHs, Available Cyanide, Ammonia

and pH

Table 8 2014 Soil Analytical Results Metals

Table 9 2014 Soil Analytical Results Phenols

7.3 Part 201 Soil Cleanup Criteria

The concentrations of the COPCs in soil samples collected at the Site were compared

to the MDEQs December 30, 2013 Part 201 nonresidential soil cleanup criteria.

Nonresidential cleanup criteria were used to compare to Site data because the

property is used for recreational (i.e., Riverside Park) and industrial (i.e., NSC property)

20

purposes. In Section 11.0, potential current unacceptable exposures to the COPCs for

human health and the environment are discussed based on current and potential

future uses of the Site.

In Section 7.4, the concentrations of the COPCs in soil samples are compared to the

following Part 201 nonresidential soil cleanup criteria:

Drinking water protection (DWP);

Groundwater/surface water interface protection (GSIP);

Soil volatilization to indoor air inhalation criteria (SVIIC);

Volatile soil inhalation criteria (VSIC; ambient air);

Particulate soil inhalation criteria (PSIC; ambient air); and

Direct contact.

The MDEQs Remediation and Redevelopment Division Operational Memorandum No.

2, Attachment 5 (October 22, 2004) states that the exposure assumptions inherent in the

Part 201 soil cleanup criteria are based on dry soils. Based on a review of boring logs,

soil samples SP-2 (14-15 ft), SP-3 (17-18 ft) and SP-4 (14-15 ft) were collected below

observed saturated conditions at these boring locations. Therefore, it is more

appropriate to use groundwater samples (Section 8.0) collected near these areas to

evaluate potential unacceptable exposures to COPCs. In Section 11.0, potential

current and unacceptable exposures to the COPCs to human health are evaluated.

7.4 Evaluation of COPCs in Soil

An evaluation of COPCs in soil based on the dates of sample collection is presented

below:

7.4.1 1984 Soil Data

Tables 1 and 2 present soil data collected during the 1984 investigation conducted by

EDI. Nonresidential DWP, GSIP, SVIIC, VSIC, PSIC and direct contact criteria were

exceeded in unsaturated zone soil samples collected during the 1984 investigation.

Refer to the Soil Exceeding Part 201 Criteria Map (Figure 5) for the locations of

unsaturated zone soil samples exceeding nonresidential criteria.

The potential for COPCs in soil to leach to groundwater in such a manner that

unacceptable drinking water and GSI exposures are indicated will be assessed by

evaluating the concentrations of COPCs in groundwater (Section 8.0).

21


Table 3 presents soil data collected in October 2011. Analytical results collected from

below an observed saturated zone are noted on the table. Nonresidential DWP, GSIP,

SVIIC, VSIC, PSIC and direct contact criteria were exceeded in unsaturated zone soil

samples collected during the 2011 investigation. Refer to the Soil Exceeding Part 201

Criteria Map (Figure 5) for the locations of unsaturated zone soil samples exceeding

residential criteria.





Tables 4 and 5 present shallow soil data collected in September 2012. Nonresidential

DWP, GSIP and direct contact criteria were exceeded. SVIIC, VSIC and PSIC criteria

were not exceeded in the shallow soil samples. Refer to the Soil Exceeding Part 201







Tables 7 through 9 present data for soil samples collected in January through May 2014.

Nonresidential DWP, GSIP, SVIIC, VSIC and direct contact criteria were exceeded. PSIC

criteria were not exceeded in the soil samples. Refer to the Soil Exceeding Part 201






In Section 11.0, potential current and unacceptable exposures to the COPCs to human

health and the environment are discussed based on current and potential future uses

of the Site.

22

8.0 GROUNDWATER CHARACTERIZATION

The evaluation of COPCs in groundwater consisted of the following:

Review of gauging data for the presence/absence of NAPLs; and,

Comparison of groundwater data generated from samples collected from site

monitoring wells to the MDEQs Part 201 nonresidential groundwater cleanup

criteria.

8.1 Non-Aqueous Phase Liquids

Approximately 2-3 inches of Dense Non-aqueous phase liquids (DNAPLs) were observed

at the bottom of the monitoring wells MW-1, MW-3 and MW-5 during the groundwater

gauging/sampling event on May 29, 2014. Refer to Figure 3 for locations of MW-1, MW-

3 and MW-5. The presence of DNAPL at each location was verified with a disposable

bailer.

NAPLs were observed within the soil during previous site investigations and the 2014

remedial investigation. The locations and depths of the observed NAPLs are shown on

Figures 5 and 6.

8.2 COPCs in Groundwater

Groundwater analytical results for the individual COPCs outlined below and Part 201

nonresidential cleanup criteria for these COPCs are presented in the following tables:

Table 10 Groundwater Analytical Results VOCs, PAHs, Metals, Cyanide and

Ammonia

Table 11 Groundwater Analytical Results Phenols

8.3 Part 201 Groundwater Cleanup Criteria

The evaluation of COPCs in groundwater consisted of the comparing groundwater

data to the following Part 201 groundwater cleanup criteria:

Non-residential drinking water criteria;

GSI criteria;

Final acute value (FAV); and,

Nonresidential volatilization to indoor air inhalation criteria (GVIIC).


health are evaluated.

23

8.4 Evaluation of COPCs in Groundwater

A groundwater sampling event was conducted from May 20 through June 2, 2014.

Refer to Tables 10 and 11 for a summary of the analytical results from this event. Refer

to the Groundwater Analytical Map May 29 June 2, 2014 (Figure 7) for the

groundwater analytical data.

The May-June 2014 data indicate that the horizontal extent of COPCs in groundwater

has not been defined. The following compounds and the MDEQ cleanup criteria that

were exceeded are:

Benzene (DW, GSI, Final Acute Value (FAV));

Toluene (GSI);

Ethylbenzene (DW, GSI, FAV);

Xylenes (DW, GSI, FAV);

1,2,4-trimethylbenzene (DW, GSI);

1,3,5-trimethylbenzene (DW, GSI);

Acenaphthene (GSI);

Flourene (GSI);

Naphthalene (DW, GSI, FAV);

Phenanthrene (GSI, FAV);

2-Methylnaphthalene (GSI);

2-4-dimethylphenol (GSI);

Cresols (GSI);

Arsenic (DW, GSI, FAV);

Lead (DW, GSI);

Available Cyanide (GSI, FAV); and,

Unionized Ammonia (GSI)

The May June 2014 data indicate that the groundwater concentrations did not

exceed the nonresidential volatilization to indoor air inhalation criteria.



of the Site.

24

9.0 SOIL GAS CHARACTERIZATION

9.1 COPCs in Soil Gas

Soil gas analytical results for the individual COPCs outlined below and Part 201

nonresidential cleanup criteria for these COPCs are presented in Table 6 Soil Gas

Analytical Results.

BTEX

Naphthalene

2-methylnaphthalene

TMBs

Mercury

9.2 Part 201 Soil Gas Screening Criteria

The evaluation of COPCs in soil gas consisted of comparing soil gas data to the

Nonresidential Vapor Intrusion Deep Soil Gas Screening Level published by the MDEQ in

May 2013.


health are evaluated.

9.3 Evaluation of COPCs in Soil Gas

Refer to the Response Activity Plan Parcel 1 Riverside Park (Stantec; February 20, 2013)

for the soil gas sampling methodology. The soil gas analytical results are presented in

Table 6. The MDEQs Part 201 nonresidential vapor intrusion deep soil gas screening

levels (SGVI-nr) are presented in Table 6 for comparison purposes. SGVI-nr values are used

to evaluate vapor intrusions of COPCs into indoor air.

The data in Table 6 indicate that mercury was not detected in the soil gas samples.

The data in Table 6 and on Figure 11 indicate that SGVI-nr screening values were not

exceeded in 14 of the 15 soil gas samples collected. As indicated in Table 6, the screen

intervals of the Parcel 1 soil gas probes ranged from 3 feet to 5.5 feet bs. The screen

intervals of the Parcel 2 gas probes ranged from 1.5 feet to 4.0 feet bs. Based on the

review of boring logs presented in the Appendix B, with the exception of one boring

(VP-3), residual MGP source materials were not encountered in the upper 5 feet of the

subsurface. Residual MGP source materials were encountered in the soil gas probe VP-

3 boring at 3.5 feet to 6 feet bs. The screen of VP-3 was installed within MGP residue

from 5 feet to 5.5 feet bs. Therefore, since the VP-3 screen was installed within MGP

25

residue (source of soil gas impacts), the soil gas sample collected from VP-3 is

considered representative of residual MGP source materials (i.e. represents worst case

soil gas emissions).

The data in Table 6 indicate that the concentration of benzene in VP-3 (Parcel 1)

exceeded the SGVI-nr screening values. No exceedances of the SGVI-nr screening values

were observed on Parcel 2.



of the Site.

26

10.0 AMBIENT AIR CHARACTERIZATION

On September 18, 2014, flux chamber samples were collected at nine locations at and

around VP-3 (Figure 3). The flux chamber sample locations are identified as P1FC -01-14

through P1FC-09-14 on Figure 3. Flux chamber samples were collected at three

different times on September 18, 2014 at each sample location. The flux chamber

samples were transported to a laboratory for analysis of the following compounds by

method TO-15:

BTEX;

TMBs; and,

2-Methylnaphthalene and naphthalene.

The flux chamber analytical results are presented in Appendix F. As indicated by the

information in Appendix F, the flux chamber analytical results indicate that there are no

unacceptable exposures to the ambient air pathway.

27

11.0 ENVIRONMENTAL RECEPTORS AND PATHWAYS

Exposure to a receptor can only occur if there is a complete exposure pathway, and a

complete exposure pathway consists of the following elements as listed below (Risk

Assessment Guide for Superfund, Volume II: Environmental Evaluation Manual; USEPA,

1989).

A source of chemical;

A mechanism by which the chemical is released;

A retention or transport medium through which a chemical travels from the point of

release to the receptor location; and,

A route of exposure (ingestion, inhalation, or dermal contact) by which the

chemical enters the receptors body and causes potential adverse health effect.

If any of these elements do not exist or are not present, the exposure pathway is

considered incomplete and exposure is unlikely.

The exposure pathways that appear to be relevant to the on-Site and off-Site

environmental receptors are:

Drinking water exposure pathway (on-Site and off-Site)

Groundwater/surface water interface pathway

Volatilization to indoor air exposure pathway

Volatilization to ambient air exposure pathway

Direct contact with soil

Based on soil, groundwater and/or soil gas analytical results and background research

on the Site and surrounding area, the evaluation of the above environmental receptors

and relevant exposure pathways is presented in subsequent sections of this report.

11.1 Drinking Water Pathway

Groundwater underneath the Site is not used as a drinking water source. The drinking

water for the City of Detroit is supplied by the Detroit Water and Sewerage Department

(DWSD) that obtains fresh water from the Great Lakes System. According to the DWSD

website, the system uses fresh water from three intakes. Two intakes are located in the

Detroit River: one to the north near the mouth of Lake St. Clair (approximately 8 miles

from the Site) and one to the south near Lake Erie (approximately 14 miles from the

Site). The third intake is located in Lake Huron (approximately 61 miles from the Site). As

stated in Section 4.2, groundwater is only intermittently present underneath the parcels.

Based on the above, the drinking water pathway is not relevant and the drinking water

criteria are not applicable.

28

11.2 Volatilization of COPCs in Soil and Groundwater to Indoor Air

There are no buildings situated on Parcels 1, 2 and 2A. Therefore, unacceptable indoor

air exposures are not indicated. Because of the lack of buildings and since buildings

are not planned to be constructed on the parcels, the indoor air pathway is not

relevant and the Part 201 soil and groundwater indoor air criteria are not applicable.

11.3 Volatilization of COPCs in Soil to Ambient Air

11.3.1 Parcel 1

This pathway is relevant; however, for reasons discussed below there are no

unacceptable exposures. The data in Table 6 indicate that the concentration of

benzene in VP-3 exceeded the SGVI-nr screening values. However, as described in

Response Activity Plan Parcel 1 Riverside Park (Stantec; February 20, 2013), the

concentrations of COPCs in the VP-3 soil gas do not result in unacceptable ambient air

exposures to recreational users. To further evaluate potential ambient air risks, the

following activities were conducted:

Ambient air concentrations of COPCs detected in the VP-3 soil gas sample were

estimated by modeling the vapor flux rates of COPCs from soil gas;

The risk associated with the modeled concentrations of COPCs in ambient air was

then calculated and the risks were determined to be acceptable (i.e, no

unacceptable risk) per Part 201; and,

As indicated by the information in Appendix F, the flux chamber analytical results

indicate that there are no unacceptable ambient air exposures.

During the 2014 remedial investigation, a soil sample collected from the P1SB-105-

14/MW-1 (8-13) location indicated benzene, naphthalene and phenanthrene

concentrations exceeding VSIC. Based on the presence of clay from the ground

surface to 13.5 feet bs, there are no unacceptable ambient air exposures.

29

11.3.2 Parcel 2


unacceptable exposures. The data in Table 6 indicate that the concentrations of

COPCs in the soil gas samples did not exceed the SGVI-nr screening values. Based on this

information, there are no unacceptable ambient air exposures on Parcel 2.

11.3.3 Parcel 2A


unacceptable exposures. Parcel 2A consists of railroad property and is maintained by

NSC. Access to Parcel 2A is reasonably restricted by fencing separating Parcel 2A from

public activities on Parcel 1 and Parcel 2. Based on this information and the ambient air

assessment completed around VP-3, there are no unacceptable ambient air exposures

on Parcel 2A.

11.4 Direct Contact with COPCs in Soil

11.4.1 Parcel 1

Potential unacceptable exposures to the direct contact pathway were evaluated by

comparing the concentrations of COPCs in soil to nonresidential direct contact criteria.

The soil samples that contained COPCs in excess of nonresidential direct contact

criteria are presented on Figures 5 and 6. As indicated on these figures and the soil

analytical tables, none of the soil samples that exceeded the direct contact criteria on

Parcel 1 were collected at the surface. The soil samples exceeding direct contact

criteria were identified at depths ranging from 7.5 to 15 feet bs. Based on the depth of

the soil exceeding the direct contact criteria, there are no current unacceptable

exposures on Parcel 1 to the direct contact pathway. However, as previously noted the

DIBC appears to have completed subsurface activities along the northeastern

boundary of Parcel 1 since the 2012 site investigation. It may be necessary for the DIBC

or the City of Detroit to further evaluate the area disturbed by the DIBC to ensure

exacerbation of subsurface contamination hasnt occurred. Future potential direct

contact exposures will be prevented by conducting additional interim response actions

and/or restricting subsurface activities.

11.4.2 Parcel 2




criteria are presented on Figures 5 and 6. The soil samples exceeding direct contact

criteria on Parcel 2 were identified at depths ranging from 0.5 to 9 feet bs. The shallow

30

soil sample exceeding direct contact on Parcel 2 (P2SB-70-14 0.5-2 bs) is located

beneath the asphalt parking lot. The soil sample (P2SB-92-14 7-9 bs) exceeding direct

contact criteria within the grassy area of Parcel 2 is at a depth of 7 to 9 feet bs.

Additionally, as shown in Appendix C, a PVC membrane was emplaced within the

grassy areas of Parcel 2 to prevent direct contact exposure. Based on access to Parcel

2 being restricted by a locked gate, the presence of asphalt and the PVC membrane,

there are no current unacceptable exposures on Parcel 2 to the direct contact

pathway. Future potential direct contact exposures will be prevented by conducting

additional interim response actions and/or restricting subsurface activities.

11.4.3 Parcel 2A




criteria are presented on Figures 5 and 6. Soil samples collected on Parcel 2A did not

exceed the direct contact criteria. Based on access to Parcel 2A being reasonably

restricted there are no current unacceptable exposures on Parcel 2A to the direct

contact pathway. Future potential direct contact exposures will be prevented by

conducting additional interim response actions and/or restricting subsurface activities.

11.5 Groundwater/Surface Water Interface Pathway

Concentrations of COPCs in groundwater samples collected from monitoring wells

located near the river exceed generic GSI and FAV criteria. The exceedances are

shown on Table 10. Based on these data and the proximity of the monitoring wells to

the Detroit River, the evaluation of potential unacceptable impacts to the river is

warranted.

31

12.0 CONCLUSIONS

The following conclusions were derived based on the information presented in this

Report:

The former MGP, tar distillation, Pintsch gas plant and toluene production

structures have been identified in historical maps and photographs as the

primary potential contaminant source areas.

Oily substances and/or tar-like materials were observed at boring locations

advanced in proximity to the former MGP, tar distillation, toluene production

structures and Pintsch gas plant structures.

Current unacceptable exposures to the drinking water pathway are not

occurring because Site groundwater is not used as a drinking water source.

Future potential unacceptable drinking water exposure can be prevented by

restricting groundwater uses.

There are no buildings situated on Parcels 1, 2 and 2A. Therefore, there are no

unacceptable indoor air exposures occurring.

Concentrations of COPCs in groundwater samples collected from monitoring

wells located near the river exceed generic GSI criteria and FAV screening levels.

A Notice of Exceedance of Groundwater/Surface Water Interface Criterion

Based on Acute Toxicity letter was submitted to the MDEQ on June 25, 2014.

Additionally, a Notice of Intent to Evaluate Final Acute Value Exceedances letter

was submitted to the MDEQ on July 21, 2014. As discussed in Section 14.0 of this

Report, future response actions include a Request for Mixing Zone Determination

and Feasibility Analysis. These response actions will satisfy the requirements

outlined in the July 21, 2014 letter to commence activities to evaluate the FAV

exceedances.

Based on visual observations, the native clay unit observed from 26 to 36 feet bs

at the Site delineates the vertical extent of the impacts.

Ambient Air Exposure

o Ambient air concentrations of COPCs detected in the VP-3 soil gas sample

were estimated by modeling the vapor flux rates of COPCs from soil gas. This

location was chosen because the benzene soil gas concentrations at VP-3

(79,000 ppbv) was the only exceedance of the SGVI-nr screening values.

32

Based on the modeled concentrations of COPCs at VP-3 in ambient air, there

are no unacceptable risks associated with the VP-3 area (refer to the

Response Activity Plan Parcel 1 Riverside Park (Stantec; February 20, 2013).

o As indicated by the information in Appendix F, the flux chamber analytical

results indicate that there are no unacceptable ambient air exposures at any

of the parcels (Parcel 1, 2, or 2A).

o In addition, either pavement or a PVC membrane covers Parcel 2 to further

limit any potential risks. Also, access to Parcel 2A is reasonably restricted and

soil samples collected from Parcel 2A did not exceed the VSIC criteria.

Direct Contact Exposure

o There are no current unacceptable exposures to the direct contact pathway

on Parcel 1. This is concluded because the only soil samples that exceeded

direct contact criteria were identified at depths ranging from 7.5 to 15 feet

below the surface on Parcel 1. Future potential direct contact exposures will

be prevented by conducting additional interim response actions and/or

restricting subsurface activities.


on Parcel 2. This is concluded because the only soil samples that exceeded

direct contact criteria were identified at depths ranging from 0.5 to 9 feet

below the surface on Parcel 2. Access to these locations is restricted either

by pavement or a PVC membrane installed under the grassy areas on Parcel

2. Future potential direct contact exposures will be prevented by conducting

additional interim response actions and/or restricting subsurface activities.


on Parcel 2A. This is concluded because the soil samples collected on Parcel

2A did not exceed the direct contact criteria. Oily and tar-like substances

were observed on Parcel 2A at depths of 8 to 12 feet bs. Based on access to

Parcel 2A being reasonably restricted and the depth to the observed

impacts, there are no current unacceptable exposures on Parcel 2A to the

direct contact pathway. Future potential direct contact exposures will be

prevented by conducting additional interim response actions and/or

restricting subsurface activities.

33

13.0 DATA GAPS

The following potential data gaps have been identified based on the information

presented in this Report.

The lack of groundwater use and subsurface activities restrictions (i.e., Restrictive

Covenant) for the Site is a data gap. Such restrictions will likely be required to

procure a No Further Action status.

The lack of mixing zone-based GSI criteria is a data gap. A request to develop

mixing zone-based GSI criteria will be submitted to the MDEQ.

The lack of location and depth information for the utilities located along the east

side of Parcel 1 is a data gap. The origin of these utilities is unknown. The utility

location and construction information should be obtained by the City of Detroit for

the utilities that have been installed on their property (if possible).

The lack of soil and groundwater analytical data from the east side of Parcel 1 is a

data gap. Soil borings/monitoring wells can be installed in this area after utility

information is obtained by the City of Detroit.

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14.0 ADDITIONAL FUTURE RESPONSE ACTIONS

The objectives of the future response actions are to:

Further define the extent of residual MGP subsurface source materials within and

around potential contaminant source areas.

o Additional site investigation activities will be completed to further define the

extent of any remaining MGP impacts.

Complete additional evaluation of potential unacceptable impacts to the Detroit

River.

o A Request for a Mixing Zone Determination will be completed and submitted

to the MDEQ. The Mixing Zone Determination will request site-specific

groundwater/surface water interface criteria for the interface with the Detroit

River. Prior to the preparation of the Request for Mixing Zone Determination,

an evaluation will be completed to determine if additional data are required

to complete the Request. Additional data collection may include, but is not

limited to, monitoring well installation and groundwater sampling events.

Complete a Feasibility Analysis to determine the appropriate remedial action plan.

o Following receipt of the additional investigation data and the Request for

Mixing Zone Determination, a Feasibility Analysis will be completed. The

Feasibility Analysis will include options for remediation or elimination of

exposure pathways and the data required to complete this evaluation.

Stantec Report on Riverside Park

Documents

Transcript of Stantec Report on Riverside Park