10.2.6_-_2012b_-_Proposed_Plan_Nov_2012.pdf

FINAL

DUPONT CHAMBERS WORKS FUSRAP SITE

PROPOSED PLAN

November 2012

U.S. ARMY CORPS OF ENGINEERS

PHILADELPHIA DISTRICT

FORMERLY UTILIZED SITES REMEDIAL ACTION PROGRAM

DuPont Chambers Works FUSRAP Site FINAL Proposed Plan

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TABLE OF CONTENTS

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

Purpose of Proposed Plan .................................................................................... 1-1 1.1

Preferred Remedial Alternative ........................................................................... 1-2 1.2

Public Participation .............................................................................................. 1-4 1.3

2.0 SITE BACKGROUND ...................................................................................... 2-1

Site History .......................................................................................................... 2-1 2.1

Previous Investigations ........................................................................................ 2-2 2.2

3.0 SITE CHARACTERISTICS............................................................................. 3-1

Environmental Setting ......................................................................................... 3-1 3.1

Nature and Extent of Contamination ................................................................... 3-3 3.2

3.2.1 Soils ...................................................................................................................... 3-3

3.2.2 Groundwater ........................................................................................................ 3-4

Contaminant Fate and Transport .......................................................................... 3-5 3.3

4.0 SCOPE AND ROLE OF THE REMEDIAL ACTION .................................. 4-1

5.0 SUMMARY OF SITE RISKS........................................................................... 5-1

Human Health Risk Assessment .......................................................................... 5-1 5.1

Ecological Risk .................................................................................................... 5-6 5.2

6.0 REMEDIAL ACTION OBJECTIVES ............................................................ 6-1

Media-Specific RAOs .......................................................................................... 6-1 6.1

Constituents of Concern ....................................................................................... 6-2 6.2

Applicable or Relevant and Appropriate Requirements ...................................... 6-2 6.3

Development of Remediation Goals (RGs) ......................................................... 6-3 6.4

Area and Volume of Contaminated Media .......................................................... 6-5 6.5

7.0 SUMMARY OF REMEDIAL ALTERNATIVES .......................................... 7-1

Alternatives S1 and GW1: No Action ................................................................ 7-1 7.1

Soil Alternatives................................................................................................... 7-1 7.2

7.2.1 Alternative S2: Excavation Followed by Off-Site Disposal ................................ 7-2

7.2.2 Alternative S3: Excavation, Treatment and Off-Site Disposal ........................... 7-3

Groundwater Alternatives .................................................................................... 7-5 7.3

7.3.1 Alternative GW2: Ex Situ Groundwater Treatment ............................................ 7-7

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7.3.2 Alternative GW3: Monitored Natural Attenuation (MNA) .................................. 7-8

Other Common Elements ..................................................................................... 7-9 7.4

8.0 EVALUATION OF REMEDIAL ALTERNATIVES .................................... 8-1

Threshold Criteria ................................................................................................ 8-3 8.1

Primary Balancing Criteria .................................................................................. 8-4 8.2

Modifying Criteria ............................................................................................... 8-7 8.3

9.0 PREFERRED ALTERNATIVE ....................................................................... 9-1

10.0 COMMUNITY PARTICIPATION ................................................................ 10-1

11.0 REFERENCES ................................................................................................. 11-1

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LIST OF TABLES

Table 5-1: Results of Radiological Dose and Risk Assessment ................................................. 5-4

Table 5-2: Results of Chemical Risk Assessment ...................................................................... 5-5

Table 7-1: Summary of Remedial Action Alternatives .............................................................. 7-1

Table 8-1: Comparative Analysis of Alternatives – Soil ............................................................ 8-2

Table 8-2: Comparative Analysis of Alternatives – Groundwater ............................................. 8-2

LIST OF FIGURES

Figure 2-1 Location of DuPont Chambers Works

Figure 2-2 Designations of Operable Units (OUs) and Areas of Concern (AOCs)

Figure 3-1 Total Uranium Concentrations in AOC 1, Cross Section View (A-A’)

Figure 3-2 Total Uranium Concentrations in AOC 2, Cross Section View (A-A’)

Figure 3-3 Total Uranium Concentrations in AOC 6 (OU 3), Cross Section View (B-B’) under East Road

Figure 3-4 Total Uranium Concentrations in OU 1 Groundwater, A Aquifer (AOCs 1 and 2)

Figure 3-5 Total Uranium Concentrations in OU 1 Groundwater, B Aquifer (AOCs 1 and 2)

Figure 3-6 Total Uranium Concentrations in AOC 6 Groundwater, B Aquifer

Figure 3-7 Area of Interest 1 (AOI 1) Well Locations (AOC 4)

Figure 5-1 Location of Exposure Units and Areas Addressed in FS

Figure 5-2 General Conceptual Site Model

Figure 6-1 Total Uranium Concentrations in Soil for AOC 1

Figure 6-2 Total Uranium Concentrations in Soil for AOC 2

Figure 6-3 Total Uranium Concentrations in Soil for AOC 6

Figure 7-1 Assumed Excavation Cutlines for OU 1

Figure 7-2 Assumed Excavation Cutlines for AOC 6

Figure 7-3 Soil Excavation Location and Treatment Diagram

Figure 7-4 Schematic of Soil Sorting with Segmented Gate System

Figure 7-5 Uranium in Groundwater - AOC 1

Figure 7-6 Uranium in Groundwater - AOC 2

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Figure 7-7 Uranium in Groundwater - AOC 6

Figure 7-8 Conceptual Layout - Groundwater Treatment OU 1

Figure 7-9 Conceptual Layout - Groundwater Treatment AOC 6

Figure 8-1 Detailed Analysis Criteria for the Evaluation of Remedial Alternatives

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LIST OF ACRONYMS AND ABBREVIATIONS

AEC Atomic Energy Commission

AOC(s) Area(s) of Concern

AOI(s) Area(s) of Interest

ARARs Applicable or Relevant and Appropriate Requirements bgs below ground surface

BNI Bechtel National, Inc.

BRA Baseline Risk Assessment

BTEX benzene, toluene, ethylbenzene, xylene

CABRERA Cabrera Services Inc.

CDD Central Drainage Ditch

CEA Classification Exception Area

CERCLA Comprehensive Environmental Response, Compensation and Liability Act

COC(s) Constituent(s) of Concern

COPC(s) Constituent(s) of Potential Concern

COPEC(s) Constituent(s) of Potential Ecological Concern

CSM Conceptual Site Model

DOE U.S. Department of Energy

DuPont E.I. DuPont de Nemours & Company

EU(s) exposure unit(s)

FS Feasibility Study ft feet/foot

FUSRAP Formerly Utilized Sites Remedial Action Program

GAC Granular Activated Carbon

HHRA Human Health Risk Assessment

HI Hazard Index

ILCR(s) Incremental Lifetime Cancer Risk(s)

ISV investigative screening value

LNAPL light non-aqueous phase liquid

LUC(s) land use control(s)

MCL maximum contaminant level

MNA monitored natural attenuation mrem/yr millirem per year µg/L micrograms per liter

MED Manhattan Engineer District

NCP National Oil and Hazardous Substances Pollution Contingency Plan

NAVD 88 North American Vertical Datum of 1988

NJAC New Jersey Administrative Code

NJDEP New Jersey Department of Environmental Protection

O&M operation and maintenance

OU(s) Operable Unit(s)

ORNL Oak Ridge National Laboratory pCi/g picocuries per gram

Ra-226 radium-226

RAGS Risk Assessment Guidance for Superfund

RAO(s) remedial action objective(s)

RCRA Resource Conservation and Recovery Act

RESRAD RESidual RADioactivity

RG remediation goal

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RI Remedial Investigation

RME Reasonable Maximum Exposure

ROD Record of Decision

SGS Segmented Gate System

SLERA Screening-Level Ecological Risk Assessment

SWMU solid waste management unit

Th-230 thorium-230

U-234 uranium-234

U-235 uranium-235

U-238 uranium-238

U(4+) tetravalent uranium ion

U(6+) hexavalent uranium ion

USACE U.S. Army Corps of Engineers

USEPA U.S. Environmental Protection Agency yd3 cubic yard

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GLOSSARY OF TERMS

Technical or unfamiliar terms (italicized in text) are defined below for reference purposes.

Adsorption: A process in which a substance (e.g., contaminant) accumulates on the surface of a solid material, forming a thin film, often only one molecule thick. Adsorption is the process that transfers contaminants from air or water onto the surfaces of activated carbon particles.

Aquifer: An underground, porous layer of sand or rock or group of layers that contains water and can be used as a source of groundwater to supply wells and springs.

Aquitard: A water-saturated soil or rock layer whose permeability is so low it is not capable of transmitting any useful amount of water.

Burrito Bag: A specialized waste transport bag with a four-flap enclosure method utilized for top loading; most commonly used when bulk-loading soil or debris into a container for transport.

Granular Activated Carbon Canister:

A component of a treatment system, acting as a filter, used to remove organics and other contaminants from air or water. The carbon has been processed (or ‘activated’) to make it extremely porous and capable of attracting the contaminants (by adsorption) as the air or water passes through the canister.

Isopleth: On a map, a line connecting points that have the same numerical value, such as a topographic contour line.

Light Non-Aqueous Phase Liquid

(LNAPL)

Organic liquids that are relatively insoluble (do not mix easily) in water and are less dense than water. As a result, LNAPLs, such as oil and petroleum chemicals float on the surface of the water table, forming a distinct layer on top of the water.

Limited Restricted Use Remedial Action:

Under the New Jersey Administrative Code; “any remedial action that requires the continued use of institutional controls but does not require the use of an engineering control.” (NJAC 7:28-12.3 Definitions).

Monitored Natural Attenuation

A cleanup approach that relies on natural attenuation processes to reduce (or lessen) the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater over time. The in situ (in place) processes include absorption, adsorption, degradation, dilution, and/or transformation.

North American Vertical Datum of

1988 (NAVD 88)

A vertical control datum used for measuring the elevation of points on the Earth's surface. NAVD 88 is the official vertical datum in the United States and Canada.

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GLOSSARY OF TERMS (continued)

Oxidizing Environment:

Environmental conditions characterized by an abundance of oxygen or the loss of electrons from an ion. Oxidizers (e.g., oxygen, chlorine, and fluorine ions) combine with reducing agents in a redox reaction. Rusting is an example of an oxidizing reaction.

Radionuclide: A radioactive particle with a distinct atomic weight number.

Radionuclides undergo spontaneous change by emission of charged particles and/or gamma rays, a change known as radioactive decay.

Reasonable Maximum Exposure

(RME):

In a risk assessment, the RME is the highest level of human exposure to contaminants that could reasonably be expected to occur.

Redox Chemical reactions in which atoms have their oxidation states changed. Generally, redox reactions refer to reactions that involve the transfer of electrons between ions.

Reducing Environment:

Environmental conditions characterized by little or no free oxygen or the abundance of hydrogen or electrons. The gain of electrons by an ion or molecule. The metals potassium, calcium, barium, sodium and magnesium are common reducing ions.

Residual Contamination:

The contamination remaining in the environment after a completed cleanup (response) action.

Resin: Solid or semi-solid viscous organic substances, like shellac or lacquer of plant origin.

Response Action: A response action is a short-term removal action or a long-term remedial action, authorized under CERCLA that is taken at a site to address releases of hazardous substances.

Restricted Use Remedial Action:

Under the New Jersey Administrative Code; “any remedial action that requires the continued use of engineering and institutional controls in order to meet the established health risk or environmental standards.” (NJAC 7:28-12.3 Definitions).

Segmented Gate System:

A cleanup technology that physically separates soils based on their level of radioactivity. The term is used generically in this document.

There are a number of vendors for similar systems with similar names, such as ‘radiological soil sorting system’ or ‘soil sorting survey system’.

Unrestricted Use Remedial Action:

Under the New Jersey Administrative Code; “any remedial action that does not require the continued use of engineering or institutional controls in order to meet the established standards.” (NJAC 7:28-12.3 Definitions).

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Volatile Organic Compounds:

Organic liquids with a high vapor pressure that evaporate readily at normal temperatures and pressures.

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1.0 INTRODUCTION

The U.S. Army Corps of Engineers (USACE) - Philadelphia District is conducting the environmental restoration of the DuPont Formerly Utilized Sites Remedial Action Program

(FUSRAP) Chambers Works Site (Chambers Works). As a part of the restoration efforts, USACE is addressing radiological contamination at the Chambers Works, resulting from past uranium refinement processes performed for the Manhattan Engineer District (MED) and

Atomic Energy Commission (AEC) in the early years of the nation’s atomic energy program.

USACE is issuing this Proposed Plan as part of its public participation responsibilities under the requirements of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (CERCLA), 42 United States Code (U.S.C.) § 9617(a), and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 Code of Federal Regulations

(CFR) § 300.430(f)(2).

Chambers Works, located in Deepwater, NJ, is an active chemical manufacturing facility owned and operated by E.I. DuPont de Nemours & Company (DuPont). From 1942 to 1947, the MED and AEC (succeeded by the U.S. Department of Energy, [DOE]) contracted with DuPont to process uranium compounds and uranium scrap to produce uranium tetrafluoride, uranium hexafluoride and a small quantity of uranium metal. For simplicity, throughout this plan MED will be used to describe the work related to the nation’s early atomic energy program whether or not the activities were performed under contract to MED or AEC. These activities resulted in residual radiological contamination at the site. USACE is utilizing the administrative, procedural, and regulatory provisions of the CERCLA and the NCP to guide the FUSRAP investigation and response action (including remedial action) at three operable units (OUs) within Chambers Works.

Purpose of Proposed Plan 1.1

This Proposed Plan describes the remedial alternatives considered for addressing soil and groundwater contamination in OU 1 and Area of Concern (AOC) 6 (which is part of OU 3), and identifies the USACE’s preferred remedial alterative(s) and supporting rationale. The other

FUSRAP areas investigated during the Sitewide Remedial Investigation (RI) do not require a response action under CERCLA. The maximum risk and dose for OU 2 (consisting of AOC 3

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and AOC 5) and AOC 4 (a part of OU 3) are within acceptable risk and dose criteria (Section

5.1). As a result, USACE is planning no further action at these FUSRAP areas.

Only FUSRAP-eligible contamination will drive USACE’s response action in OU 1 (consisting of AOCs 1 and 2) and AOC 6. The constituents determined to be eligible for a response action under FUSRAP include the radioactive constituents associated with the MED uranium processing activities performed at Chambers Works. These constituents are primarily uranium, thorium, radium and the short-lived decay products of these elements (Cabrera Services, Inc.

[CABRERA] 2011a). The scope of this plan does not include addressing non-FUSRAP-related contamination that may be associated with past DuPont chemical manufacturing operations unless it happens to be commingled with materials related to the FUSRAP remediation. Non-

FUSRAP contaminants will be removed along with the eligible FUSRAP contaminants to the extent necessary to successfully complete the FUSRAP response action.

The site characteristics, nature and extent of contamination, associated human health and ecological risks, and possible remedial action alternatives are summarized herein with more detailed information found in the following documents:

Sitewide RI Report for All Operable Units, DuPont Chambers Works FUSRAP Site (CABRERA 2011b), Baseline Risk Assessment (BRA) DuPont Chambers Works FUSRAP Site (CABRERA 2011c), and

Feasibility Study (FS), DuPont Chambers Works FUSRAP Site (CABRERA 2012).

The RI, BRA, FS, and other project-related documents are available in the administrative record file located at the USACE Philadelphia District Office and at the Salem Community College

Library. USACE encourages the public to review available material about the DuPont Chambers

Works FUSRAP Site and to comment on the preferred remedial action alternative presented in this Proposed Plan. At the conclusion of the public comment period, the USACE will fully consider and respond to all significant comments received. USACE will then select the remedial action for the DuPont Chambers Works FUSRAP site in the Record of Decision (ROD).

Preferred Remedial Alternative 1.2

This Proposed Plan summarizes the findings of the RI, BRA, and FS in order to present

USACE’s preliminary recommendation, the preferred remedial alternative for addressing MED-

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related contamination, and to solicit public and regulatory agency comments pertaining to the remedial alternative evaluation and selection process. The USACE has carefully studied the

MED-related areas and believes the best way to protect human health and the environment is to implement the preferred remedial alternative. The preferred remedial alternative includes the following components:

1) Excavate contaminated soils above the remediation goal (RG)(or ‘cleanup goal’);

2) Transport and dispose contaminated soils at a permitted off-site disposal facility;

3) Employ monitored natural attenuation, or MNA, to address the residual uranium groundwater concentrations through a defined monitoring program after completion of the soil response action; and

4) Use land use controls (LUCs) to limit potential onsite exposure to contaminants during remedial action activities.

Excavation and disposal of contaminated soil will eliminate the source of groundwater contamination and significantly reduce contaminant concentrations in groundwater. This reduction in groundwater concentrations is expected because contaminated groundwater will also be removed during any soil excavation (CABRERA 2012). The defined monitoring program associated with MNA will document residual groundwater contamination after completion of the soil remedial action (excavation) and the effectiveness of natural attenuation processes over time.

USACE expects that residual levels of contamination will remain in groundwater after excavation of soil but at levels well suited for the selection of excavation combined with MNA as a preferred alternative.

USACE proposes a demonstration period of two to five years to evaluate the effectiveness of

MNA. The demonstration timeframe will depend on results of both analytical sampling results and statistical trend analysis. During this time, USACE will collect both field measurements and analytical data to demonstrate that naturally occurring in situ processes are working to reduce contaminant concentrations. Assuming that MNA is confirmed to be effective during the demonstration period, monitoring will continue until compliance with remedial action objectives

(RAOs) has been achieved for all monitoring wells included in the program.

LUCs will be implemented as part of the preferred alternative to restrict access and protect workers during remedial action activities and rely on existing DuPont site access restrictions and

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controls. The LUCs for this site include physical, legal, and administrative controls and are designed to protect public health and the environment by limiting land use and onsite activities to prevent exposure to contaminants. LUCs implemented during the remedial action to protect site workers will include but are not limited to fencing, site access restrictions, and current DuPont procedures and safeguards that control the disturbance of soils (excavation permits) and restrict the use of groundwater as a potable source.

The preferred remedial alternative is anticipated to result in a permanent and irreversible reduction of soil and groundwater contamination since the source of radioactive contamination will be removed. Based on the current and most reasonably anticipated future land use for

Chambers Works, the USACE developed an RG and evaluated potential remedial alternatives suitable for the continued industrial use of the property. This means that upon completion of the remedial action to the industrial use cleanup goal, limited contamination could remain onsite but at levels which are safe for industrial use. After excavation, USACE will assess the contamination and perform a dose assessment in order to evaluate the effectiveness of the remedial action. Residual contamination is expected to be very low and could possibly allow for a future unrestricted use of the areas with regard to FUSRAP contaminants.

Public Participation 1.3

USACE is requesting public review and comment on the preferred alternative as well as other alternatives presented in this plan. At the conclusion of the public comment period USACE will review comments, including both those from the public and from the New Jersey Department of

Environmental Protection (NJDEP). After careful consideration of comments, USACE will select a remedial action for the soil and groundwater in the FUSRAP areas at Chambers Works.

As the lead agency for the DuPont Chambers Works FUSRAP site, USACE may ultimately select the preferred alternative for remediation of the soil and groundwater, modify aspects of the preferred alternative, or select any of the other alternatives presented in this plan based on public comments received. Consequently, USACE encourages the public to review available documents and provide comments. In order to receive consideration, commenters must submit their comments to USACE by the dates specified in Section 10 of this plan.

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2.0 SITE BACKGROUND

The Chambers Works is located in Pennsville and Carneys Point Townships, along the southeastern shore of the Delaware River, north of the I-295 Delaware Memorial Bridge, and adjacent to the residential community of Deepwater, NJ. The location of the DuPont property is shown in Figure 2-1. The Chambers Works extends 2.7 miles between Helms Cove to the north and the Salem Canal to the south. Henby Creek separates the active Chambers Works manufacturing area from the former Carneys Point Dye Works. The Pennsylvania and Reading

Seashore Line railroad track bounds the property to the east.

Site History 2.1

MED operations involving uranium began at Chambers Works in 1942, when MED contracted with DuPont to perform several uranium-processing activities. In 1946, all MED activities were transferred to the AEC, and DuPont continued research for AEC until late 1947. The DuPont contracts with MED and/or AEC involved uranium refinement operations. In addition to the uranium refinement, Chambers Works also converted quantities of green salt (uranium tetrafluoride) to uranium hexafluoride in a process known as the hexafluoride process. Uranium refinement using the brown oxide, green salt, and recovery processes were also conducted. No uranium enrichment or depletion processes were conducted at Chambers Works.

Based on the nature and location of past MED activities, USACE identified six AOCs at

Chambers Works for investigation. To facilitate further investigation and remedial decisions, the

USACE organized the AOCs into the following three OUs for a phased investigation under

FUSRAP:

OU 1 consists of AOC 1, Former Building 845 and AOC 2, the F Corral. Production areas where uranium recovery and processing took place between 1943 and 1947.

Residual processing wastes were discharged into a wooden trough. The wooden trough is still in existence, collects storm water, and discharges to the Central Drainage Ditch (CDD) located in AOC 1. Production of uranium metal occurred in AOC 2 in former Building 708.

OU 2 consists of AOC 3, CDD and AOC 5, Building J-26 Area. These AOCs include the location of a former laboratory building (J-16) and the drainage ditches leading away from uranium production areas through which processing wastes were discharged.

OU 3: AOC 4, the Historical Lagoon and AOC 6, the East Area. These AOCs were primarily disposal areas for building rubble, discarded equipment, and process wastes.

After MED activities began, the East Area was also used by DuPont for the production of

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fluorinated solvents and fluorinated lubricants. MED uranium processing did not take place in the East Area.

Figure 2-2 shows the location of each FUSRAP OU/AOC with respect to DuPont’s active manufacturing areas.

Previous Investigations 2.2

After MED operations ceased, a number of cleanup activities occurred at the Site consistent with regulatory standards and guidelines in effect at the time. Later, additional radiation surveys and investigations were conducted and resulted in Chambers Works being designated for investigation and potential cleanup under FUSRAP. These investigations are briefly summarized below with more detailed information found in the Sitewide RI Report (CABRERA 2011b):

1948/1949: AEC conducted radiological surveys and decontamination of building surfaces, based on the existing radiological criteria of the time, and then released the buildings back to DuPont. DuPont demolished Building J-16 in AOC 5, excavated several feet of soil from beneath the building, and constructed Building J-26 over the former Building J-16 footprint (DOE 1996).

1977: Oak Ridge National Laboratory (ORNL) conducted a radiation survey of the Chambers Works to determine if contamination existed at the site at levels above the current guidelines. Results showed that exposure rates in the F Parking Corral (AOC 2) were consistent with background radiation levels, while the external gamma radiation levels along the CDD (AOC 3) and the East Area (AOC 6) exceeded background levels.

Based on these results, DOE designated Chambers Works as a FUSRAP site (ORNL 1978).

1983: Bechtel National, Inc. (BNI) performed a radiation survey of the Chambers Works to define the areas and boundaries of contamination identified in 1977. In the F Parking Corral (AOC 2), near-surface gamma radiation readings were below the average background level, with the exception of one. Based upon 19 boreholes, contamination was indicated in layers to a depth greater than nine feet (ft). Results from the analysis of two soil samples indicated that uranium-238 (U-238) was the major contaminant with concentrations ranging from 0.9 to 4,347 picocuries per gram (pCi/g). Eleven groundwater samples were also collected from the boreholes, with total uranium results ranging from background value of 1.8 to a maximum of 105,105 picocuries per liter (BNI 1985).

1988 - Present: Unrelated to the FUSRAP work, DuPont has been conducting Resource Conservation and Recovery Act (RCRA) corrective actions at Chambers Works since 1988 to address contamination from its chemical manufacturing activities. In accordance with the facility’s RCRA permit, DuPont has been operating an extensive sitewide groundwater pump and treat system to control off-site groundwater migration of chemical contaminants (unrelated to FUSRAP). The system has been effective in hydraulically

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containing contaminants in groundwater within the property boundaries. As part of its RCRA investigation, DuPont has designated the areas of former MED activity as Solid Waste Management Unit (SWMU) 33 but has not performed remediation work in these areas.

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3.0 SITE CHARACTERISTICS

Environmental Setting 3.1

Topography: The Chambers Works complex is located within the Lowland Subprovince of the

Atlantic Coastal Plain physiographic province. The surrounding topography is gently rolling, with elevations from zero to 85 ft (top of landfill elevation) North American Vertical Datum of

1988 (NAVD 88). Elevations at the complex are typically approximately 10 ft above NAVD 88.

Drainage: A major drainage feature at the Chambers Works is the CDD. The water flow direction of the CDD is eastward with water depths averaging one to two ft. The CDD exhibits perennial water flow. Historically, the CDD connected MED operational areas with the

Historical Lagoon A. Lagoon A was composed of three settling basins – referred to as the A, B, and C Basins. Basins A and C are no longer in use and have been closed in accordance with regulatory requirements by DuPont. The former Basin B area is designated as RCRA SWMU

15. The lower half of Basin B is currently being used for site storm-water collection whereas the remaining portion of Basin B has undergone remediation and received clean closure approval.

Surface Water Features: The Delaware River is tidal and brackish at Deepwater, NJ and is not a potable water source in the area of Chambers Works; however, the river is a major supplier of potable water to communities upstream or north of Chambers Works. At the Reedy Point

Delaware tide gage (station ID 8551910) located across the Delaware from Chambers Works, the yearly mean tide range is 5.34 ft and the mean tide level is -0.12 ft NAVD 88. Mean high tide is

2.87 ft NAVD 88 while mean low tide is -2.97 ft NAVD 88.

Land Uses: The Chambers Works is currently zoned for industrial use and expected to remain industrial into the future. The land use directly adjacent to Chambers Works is a mix of recreational (forested/wetlands areas) and light industrial; although 43% of Salem County is used for agricultural purposes.

Regional and Local Geology: Native site soils are of alluvial and palustrine (marsh) origin, but have been substantially modified by landfilling and construction activities. The land along the shoreline has most likely been accreted as point-bar deposits from the Delaware River, or possibly, from over-bank deposition during periodic flooding, which has resulted in the

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formation of a natural levee. Behind these shoreline deposits, which consist of sands and silty sands, there once existed a tidal marsh consisting of silty clays, with an elevation near sea level.

DuPont has gradually expanded Chambers Works by filling in the marsh and low lying areas.

Generally, up to a distance of 200 yards from the river’s edge, the soils at sea-level are the naturally occurring marsh deposits, while the soils above sea level are fill material (DERS 1995).

Regional and Local Hydrogeology: The sedimentary deposits beneath Chambers Works can be divided into five major sequences consisting of aquifers and aquitards (nomenclature used by

DuPont, and for clarity, adopted for use in the RI):

(1) The A and B aquifers and A-B and B-C aquitards: The A aquifer is the uppermost water-bearing zone at the Chambers Works. The B aquifer consists of sands that are interpreted to be Delaware River alluvium. The B aquifer is not widely developed as a groundwater source in Salem County, although yields of up to 1,500 gallons per minute have been reported. The A-B aquitard is discontinuous and thins to zero to the east, as well as in areas where stream channels were once present.

(2) The C aquifer: composed mainly of Pleistocene-age coarse-grained sands and gravels;

(3) The C-D aquitard: composed of clays and silts of estuarine origin.

(4) The D aquifer: consisting of coarse-grained sands and gravels. Unit is valley-fill sediment that is incised in the underlying Potomac Group

(5) The D-E aquitard and the E and F aquifers: Cretaceous-Age sediments of the Potomac

Group, representing the lowest sedimentary sequence.

Although the surficial aquifers beneath Chambers Works are not used for drinking water, they are designated by the NJDEP as Class II groundwater. The State of New Jersey divides groundwater into classes based on groundwater use and sets corresponding water quality standards based on its designated use. Class II groundwater is designated as having a potential use as a drinking water source in the future. When groundwater quality in an area does not meet the standard, but is being monitored or treated, the State can issue an exception to the classification. An exception provides notice that there is groundwater contamination in a localized area, and suspends all designated groundwater use in the area for the specified duration of the exception.

The shallow, near surface aquifers are not used for drinking water purposes. In this area, the deeper Potomac Group (F Aquifer) is widely used as drinking water source in southern New

Jersey and Delaware.

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Nature and Extent of Contamination 3.2

The RI and BRA identified site features, assessed the nature and extent of constituents of potential concern (COPCs), and evaluated risks to human health and the environment from constituents associated with uranium processing activities conducted at Chambers Works.

USACE evaluated radioactive and chemical compounds associated with the MED activities and determined that five radionuclides were eligible for FUSRAP investigation and remediation.

They are uranium-234 (U-234), uranium-235 (U-235), U-238, thorium-230 (Th-230), and radium-226 (Ra-226). No chemical compounds were identified as FUSRAP-eligible contaminants. Further detail on the identification of eligible contaminants is included in the

Memorandum: USACE Determination of Eligible Contaminants for FUSRAP Investigation

(CABRERA 2011a). Investigation results for the FUSRAP OUs and AOCs are detailed in the

Final Sitewide RI report (CABRERA 2011b). As previously mentioned the Sitewide RI and BRA concluded that onsite soils and groundwater have been impacted by FUSRAP-eligible contaminants and required further evaluation in the FS for possible remedial actions at two areas, OU 1 and AOC 6. The nature and extent of the MED-related contamination in soils and groundwater in these areas are summarized in the following subsections.

3.2.1 Soils

The soil sampling results for OU 1, OU 2, and OU 3 were compared against an investigative screening value (ISV) of 14 pCi/g for total uranium in order to define the nature and extent of

MED-related soil contamination. Cross section views of OU 1 and AOC 6 are shown in Figures

3-1 through 3-3.

Within OU 1, uranium contamination was detected at depths up to 5.5 ft below ground surface

(bgs) in AOC 1 and to a depth of 11 ft bgs in AOC 2. Maximum uranium concentrations in

AOC 1 and AOC 2 were reported as 677 pCi/g and 16,584 pCi/g, respectively. The soil contamination above the ISV has been estimated to encompass approximately one acre within

AOC 1 and 1.7 acres within AOC 2. Figures 3-1 and 3-2 show the vertical cross section view of

MED uranium contamination across AOC 1 and AOC 2, respectively. The reader is also referred back to the Sitewide RI report, Section 4 for more detailed sampling results in OU 1

(AOC 1 and AOC 2).

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Within OU 1, elevated Ra-226 and Th-230 concentrations were identified at locations within or in close proximity to uranium source areas. At AOC 1, Ra-226 and Th-230 results in soil range from 0.4 to 2.3 pCi/g, and 0.4 pCi/g to 64 pCi/g, respectively. At AOC 2, Ra-226 and Th-230 results in soil range from 0.37 to 2.87 pCi/g, and 0.19 pCi/g to 15 pCi/g, respectively.

Soils in AOC 6 were contaminated above the ISV at depths less than four ft bgs. The highest concentration of total uranium was 3,910 pCi/g at one ft bgs. The total area of soils impacted above the ISV is approximately 4,800 square ft (0.1 acres). Figure 3-3 shows a vertical cross section view of MED uranium contamination across AOC 6. The reader is also referred to the

Sitewide RI report, Section 6 for more detailed sampling results in OU 3 (AOC 4 and AOC 6).

3.2.2 Groundwater

The extent of groundwater contamination was determined by comparison of total uranium concentrations to the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level

(MCL) of 30 micrograms per liter (µg/L). The reader is referred to the Sitewide RI report for more detailed groundwater sampling results. Uranium was detected above the MCL in both the A and

B Aquifers within OU 1. For the A Aquifer, the maximum concentrations for total uranium in

AOC 1 and AOC 2 are 26,317 µg/L and 14,027 µg/L, respectively. The horizontal extent of uranium impact to groundwater in the OU 1 A Aquifer is approximately 0.5 acres as presented in

Figure 3-4. Groundwater flow in the A Aquifer is controlled and captured by the drainage ditches. The area of impacted groundwater is located within the area of uranium-impacted soils.

In the B Aquifer in OU 1, uranium concentrations above the 30 μg/L MCL were found in two wells, and concentrations averaged 29,560 (2-MW-03B) and 167 µg/L (2-MW-05B). There is no evidence that uranium has been mobilized and transported any significant lateral distance within the B Aquifer. Vertical control is provided by the C aquifer well in this area, which has consistently shown uranium levels below the MCL. Within the B Aquifer uranium-impacted groundwater is limited to approximately 0.2 acres as presented in Figure 3-5 and is located beneath the footprint of the former Building 708.

Investigations of OU 1 groundwater have identified the presence of benzene, toluene, ethylbenzene, and xylene (BTEX) constituents in excess of their representative MCLs, as well as the presence of a light non-aqueous phase liquid (LNAPL). These organic compounds are

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typically associated with petroleum products, coal tar, and other chemical derivatives. The

LNAPL appears to be coal tar or coal tar distillate with a mixture of other compounds. Sampling for radioactivity in the LNAPL has shown uranium concentrations are at background levels.

Neither the coal tar components nor BTEX are FUSRAP eligible contaminants. These chemical constituents were not used in MED processes but are instead associated with the facility’s non-

FUSRAP chemical manufacturing operations (CABRERA 2011a).

The A Aquifer is not present in AOC 6, so the B Aquifer is nearest to ground surface. One B aquifer well in this area (located down gradient of contaminated soils) exhibited total uranium concentrations exceeding the 30 µg/L MCL, with an average uranium concentration of 267 µg/L

(6-MW-01B). Sampling methods have determined that the uranium is in the aqueous phase and has not sorbed or attached to mobile particles. The extent of contaminated groundwater in AOC

6 is shown in Figure 3-6. The isopleth, a line through all points having the same numerical value, is not centered on the impacted well but is implied to include the area of uranium contamination in soil located under East Road.

Uranium concentrations exceeded the MCL in one well in AOC 4, Area of Interest (AOI) 1

(Historical Lagoon Area), with an average of 145 g/L total uranium (well number I17-M01A) over four quarters of monitoring. This well is located within DuPont’s closed waste cell, SWMU

5 and is approximately 280 ft from the Delaware River. In this area, the groundwater flow direction in the A Aquifer is toward the river. However, the RI monitoring results have consistently shown that the uranium is not migrating toward the river. A slurry wall installed by

DuPont is located between this well and the downgradient wells near the river. Although no soil remedial action is warranted in AOC 4, it is recommended that Well I17-M01A and associated downgradient wells be included in a future monitoring program in order to confirm these conclusions and to monitor uranium concentrations in groundwater in both the A and B Aquifers in AOC 4. Figure 3-7 shows the location of this well in AOC 4, the slurry wall, and the other monitoring wells in this area. No other monitoring wells in AOC 4 exhibited groundwater contamination above 30 g/L total uranium.

Contaminant Fate and Transport 3.3

This section provides a qualitative discussion of the chemical and physical properties of uranium

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and the fate and transport mechanisms affecting its movement in the environment. Mobility is an important consideration because non-mobile compounds tend to stay in the same location instead of spreading and, by virtue of staying in the same location, are easier to clean up. The solubility of a compound is an important transport parameter in groundwater because it determines the concentration of the dissolved phase. The oxidation reduction (redox) potential of the groundwater is the primary controlling factor in determining uranium solubility and mobility.

Soluble uranium compounds are less likely to attach to soil or sediment particles, and therefore, will be more mobile in groundwater.

Uranium occurs in six oxidation states ranging from U(1+) to hexavalent uranium (U(6+)), with tetravalent uranium [U(4+)] and U(6+) being the most common oxidation states of uranium in nature. The U(4+) species typically dominates in reducing environments while the U(6+) form is prevalent in oxidizing environments (USEPA, 1999). The hexavalent form, U(6+), generally is more soluble than the tetravalent form U(4+) and therefore, more mobile in groundwater.

Chemicals that are not readily soluble in water tend to attach to soil particles and not move in the environment. Therefore, low-solubility U(4+) compounds, like uraninite are less mobile in the environment.

Groundwater in the OU 1 and AOC 6 source zones is oxidizing due to the presence of the U(6+) mineral metastudtite (uranium peroxide dihydrate), which creates hydrogen peroxide (and hydrogen) by alpha irradiation of water molecules. U(6+) compounds are quite soluble in oxidizing environments. Hydrogen peroxide is not persistent in natural environments. The available dissolved oxygen is consumed a short distance from the metastudtite source.

Therefore, due to the presence of less available dissolved oxygen, hexavalent U(6+) ions are reduced to the low-solubility tetravalent U(4+) ions. This transformation has been inferred to take place within a short distance from the source zones because dissolved uranium concentrations decrease by three orders of magnitude within a distance of 100 ft. The predominant uranium compound occurring in the reducing area of the plume is thought to be a

U(4+) species such as uraninite with lower solubility.

Due to the presence of organic contamination in the shallow Chambers Works aquifers, the groundwater is characterized by little or no dissolved oxygen. Microbial activity and organic

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contaminants in the environment can lead to reducing conditions by using up the available dissolved oxygen. Reducing groundwater conditions at Chambers Works help to limit the movement of aqueous uranium. Based upon extensive RI groundwater sampling data in both the

A and B aquifers, it has been established that due to reducing conditions in groundwater, the existing dissolved MED uranium is not mobile, either vertically or horizontally. The OU 1 groundwater plume has migrated only a very short distance (less than 100 ft) since the MED activities in the 1940s. During the RI groundwater monitoring program (2002 to 2007), the leading edge of the plume did not migrate. However, there is a potential for radiological contaminants in soil to leach into the groundwater and continue to impact the A and B Aquifers.

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4.0 SCOPE AND ROLE OF THE REMEDIAL ACTION

The primary objectives of this proposed remedial action are: (1) to address the OU 1 and AOC 6 soils containing FUSRAP-related constituents in concentrations above site-specific cleanup criteria, and (2) to minimize further impacts to groundwater in the FUSRAP AOCs in order to ensure protection of groundwater for some future use.

Under FUSRAP, the USACE is authorized to investigate and conduct a response action

(including remedial action) only for those constituents of concern (COCs) resulting from past

MED activities. The COCs are uranium including U-234, U-235, and U-238 as well as Th-230, and Ra-226. Constituents not associated with the uranium refinement processes at Chambers

Works may be remediated only if commingled with the above MED-related COCs. If commingled, USACE will remove the non-MED constituents along with FUSRAP eligible contaminants to the extent necessary to accomplish the FUSRAP response action. Therefore, the scope of this proposed response action is limited to the constituents found to be associated with

MED activities: U-234, U-235, and U-238 as well as Th-230, and Ra-226. Criteria established in the ROD will be implemented using final status surveys compatible with the Multi-Agency

Radiation Site Survey and Investigation Manual and applicable or relevant and appropriate requirements (ARARs) at all areas addressed by this response action.

Current land use at Chambers Works is industrial and expected to remain industrial well into the reasonably foreseeable future. Chambers Works has an extensive and rich manufacturing history and it is expected that the chemical manufacturing operations, although reduced in scale over recent years, will continue at the Deepwater, NJ, location under DuPont ownership. For the purposes of the FUSRAP investigation and remedial action, the USACE considers the most reasonably anticipated future land use for Chambers Works to be industrial. This is based on

DuPont’s intentions for land use, the non-FUSRAP environmental contamination that is present, surrounding land use, and the community’s expectations for the property’s continued industrial use. Therefore, based on risk assessment results (Section 5) and determination of site specific

RAOs (Section 6), the USACE is planning to clean up the FUSRAP areas to an industrial use cleanup standard.

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5.0 SUMMARY OF SITE RISKS

As part of the BRA, both a Human Health Risk Assessment (HHRA) and a Screening Level

Ecological Risk Assessment (SLERA) were performed for each exposure unit (EU) to determine the current and future effects, or risks, on human health and the environment from both radiological and non-radiological chemicals if no remedial actions were taken. For evaluation in the BRA, the six FUSRAP AOCs were grouped into five separate EUs based on physical location and receptor exposure patterns within the Chambers Works. The EUs are shown in

Figure 5-1:

EU 1 includes AOC 1 and AOC 2 (OU 1) EU 2A is AOC 3 (OU 2) EU 2B is AOC 5 (OU 2) EU 3A is AOC 4 (OU 3) EU 3B is AOC 6 (OU 3)

Human Health Risk Assessment 5.1

Four current and potential future land users were evaluated for potential exposure to radioactive and chemical contaminants. They include the industrial worker, construction worker, maintenance worker, and utility worker. Potential exposure was based on the concentration of contaminants as well as frequency and duration of the workers’ (receptors) exposure. A reasonable maximum exposure (RME) was determined for each land use scenario; the RME is the highest level of human exposure that could reasonably be expected to occur (USEPA 1989).

The industrial worker scenario was considered as the current and likely future land use scenario for

Chambers Works. Even though industrial land use is the expected and most reasonable current and future land use scenario for the site, the USACE performed a risk assessment for a residential receptor. This evaluation was only used for comparative purposes.

A Conceptual Site Model (CSM) was utilized to determine complete exposure pathways for each receptor scenario, based upon sources of contamination, contaminated media and the pathways of migration as shown in Figure 5-2. Based upon the CSM, only the soil medium was evaluated as a source of contamination. The groundwater ingestion pathway was eliminated from evaluation as no receptors are currently utilizing the groundwater beneath the Site as a potable water source; FUSRAP contamination is not likely in the future to move enough to endanger off-site users; and it is not likely that groundwater will be utilized by future…