10.2.13_-_2013_Record_of_Decision_-_DuPont_Chambers_Works_Sep_-2013.pdf

DUPONT CHAMBERS WORKS FUSRAP SITE

RECORD OF DECISION

DUPONT CHAMBERS WORKS

DEEPWATER, NEW JERSEY

August 2013

U.S. ARMY CORPS OF ENGINEERS

PHILADELPHIA DISTRICT

FORMERLY UTILIZED SITES REMEDIAL ACTION PROGRAM

[This page intentionally left blank]

Record of Decision DuPont Chambers Works FUSRAP Site FINAL i

TABLE OF CONTENTS

I. DECLARATION

A. Site Name and Location

B. Statement of Basis and Purpose

C. Assessment of the Site

D. Description of the Selected Remedy

E. Statutory Determinations

F. Record of Decision Data Certification Checklist

G. Authorizing Signatures

II. DECISION SUMMARY

A. Site Name, Location, and Description

B. Site History and Investigations

B.1 Site History

B.2 Site Investigations

B.3 Removal Action for Building Materials

B.4 Post-Remedial Investigation Groundwater Monitoring 2012

C. Community Participation

D. Scope and Role of Response Action

E. Site Characteristics

E.1 Conceptual Site Model

E.2 Surface and Subsurface Features

E.3 Sampling Strategy

E.4 Nature and Extent of Contamination

E.4.1 Soil Contamination

E.4.2 Groundwater Contamination

F. Current and Potential Future Land and Water Uses

F.1 Current Land Use

F.2 Future Land Use

F.3 Groundwater and Surface Water Uses

G. Summary of Site Risks

G.1 Human Health Risk Assessment ii

G.2 Ecological Risk Assessment

G.3 Baseline Risk Assessment Summary

H. Remedial Action Objectives

H.1 Media-Specific Remedial Action Objectives

H.2 Applicable or Relevant and Appropriate Requirements

H.3 Development of Remediation Goals

I. Description of Alternatives

I.1 Soil Remedial Alternatives

I.2 Groundwater Remedial Alternatives

I.3 Common Elements and Distinguishing Features of Each Alternative

I.4 Expected Outcomes of Each Alternative

J. Summary of Comparative Analysis of Alternatives

J.1 Overall Protection of Human Health and the Environment

J.2 Compliance with ARARs

J.3 Long-Term Effectiveness and Permanence

J.4 Reduction in Toxicity, Mobility, or Volume through Treatment

J.5 Short-Term Effectiveness

J.6 Implementability

J.7 Cost 35

J.8 State Acceptance

J.9 Community Acceptance

K. Principal Threat Wastes

L. Selected Remedy

L.1 Summary of the Rationale for the Selected Remedy

L.2 Detailed Description of the Selected Remedy

L.3 Cost Estimate for the Selected Remedy

L.4 Estimated Outcomes of the Selected Remedy

M. Statutory Determinations

M.1 Protection of Human Health and the Environment

M.2 Compliance with ARARs

M.3 Cost Effectiveness

M.4 Permanent Solutions and Alternative Treatment Technologies iii

M.5 Preference for Treatment as a Principal Element

M.6 Five-Year Review Requirements

N. Documentation of Significant Changes

III. RESPONSIVENESS SUMMARY

IV. REFERENCES

iv

LIST OF TABLES

Table 1: Results of Radiological Dose and Risk Assessment

Table 2: Results of Chemical Risk Assessment

Table 3: Comparative Analysis of Alternatives – Soil

Table 4: Comparative Analysis of Alternatives – Groundwater

Table 5: Total Cost of Selected Remedy Excavation And Disposal of Soil Combined with Monitored Natural Attenuation of Groundwater

LIST OF FIGURES

Figure 1: Location Map: DuPont Chambers Works FUSRAP Site

Figure 2: FUSRAP Operable Units and Areas of Concern

Figure 3: Conceptual Site Model

Figure 4: Impacted Soil – OU 1

Figure 5: Impacted Soil - AOC 6

Figure 6: Extent of Impacted Groundwater OU 1 (AOC 1) (2004-2007)

Figure 7: Extent of Impacted Groundwater OU 1 (AOC 2) (2004-2007)

Figure 8: Extent of Impacted Groundwater OU 3 (AOC 6) (2004-2007)

Figure 9: Location of Exposure Units and Areas Requiring Response Action

Figure 10: Excavation Areas OU 1

Figure 11: Excavation Areas AOC 6

APPENDIX

Appendix A: Summary Statistics for Sampling Results at Various Exposure Units

Table A-1: Summary Statistics – Surface Soil Sampling Results

Table A-2: Summary Statistics – All Depth Soil Sampling Results

Table A-3: Summary Statistics – Sediment and Surface Water Sampling Results

Table A-4: Summary Statistics – Groundwater Sampling Results v

ACRONYMS AND ABBREVIATIONS

AEC Atomic Energy Commission AOC(s) Area(s) of Concern ARAR Applicable or Relevant and Appropriate Requirement BNI Bechtel National, Inc.

CABRERA CABRERA Services, Inc.

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act DOE U.S. Department of Energy DuPont E.I. DuPont de Nemours & Company EPC Exposure Point Concentration ft foot (feet) FUSRAP Formerly Utilized Sites Remedial Action Program HHRA Human Health Risk Assessment mrem/yr millirem per year μg/L microgram(s) 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 Operations and Maintenance OU(s) Operable Unit(s) ORNL Oak Ridge National Laboratory pCi/g picocurie(s) per gram Ra-226 radium-226 RAGS Risk Assessment Guidance for Superfund RCRA Resource Conservation and Recovery Act RME Reasonable Maximum Exposure SWMU(s) Solid Waste Management Unit(s) Th-230 thorium-230 U-234 uranium-234 U-235 uranium-235 U-238 uranium-238 USACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency yd3 cubic yard

I. DECLARATION

A. Site Name and Location

DuPont Chambers Works FUSRAP Site State Highway 130 (Shell Road) Deepwater, New Jersey 08070

DuPont Chambers Works is an operating chemical manufacturing complex, located in Salem County, New Jersey. In the 1940s, E. I. du Pont de Nemours and Company (DuPont) performed work for the federal government in support of the nation’s early atomic energy program. The U.S. Army Corps of Engineers (USACE) is addressing residual radioactive contamination in specific areas of the property under the Formerly Utilized Sites Remedial Action Program (FUSRAP). The areas are collectively referred to as the DuPont Chambers Works FUSRAP Site.

B. Statement of Basis and Purpose

This Record of Decision presents the selected remedial action for soil and groundwater contamination at the DuPont Chambers Works FUSRAP Site (also referred to as the “Site”). As lead agency for the response action, USACE selected the remedial action in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 42 U.S.C. § 9601 et seq. and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 Code of Federal Regulations Part 300. The selection is based on information contained in the Administrative Record File for the Site and is documented in this Record of Decision. In coordination with the New Jersey Department of Environmental Protection (NJDEP), and community stakeholders, USACE reviewed and evaluated comments received on the Proposed Plan during the public comment period prior to selecting the remedial action.

Section III, the Responsiveness Summary, provides all comments received and associated responses. The State of New Jersey concurs with USACE’s selected remedy for impacted soil and groundwater at the DuPont Chambers Works FUSRAP Site.

C. Assessment of the Site

The response action for impacted soil and groundwater selected in this Record of Decision is necessary to protect the public health or welfare or the environment from actual or threatened releases of hazardous substances into the environment. The results of the Remedial Investigation and Baseline Risk Assessment identified unacceptable dose and risk at specific areas of the Site.

Therefore, the USACE evaluated a number of remedial action alternatives and selected a remedial action. The selected remedial action includes excavation and offsite disposal of contaminated soil combined with monitored natural attenuation of residual contaminants in groundwater. This remedial action provides a high level of protection to human health and the environment by removing contaminated materials, and is consistent with the continued industrial use of the property.

D. Description of the Selected Remedy

Background. In the 1940s, DuPont conducted uranium processing and research activities for the Manhattan Engineer District (MED) and/or Atomic Energy Commission (AEC). Various uranium products were produced from uranium oxides and scrap metal. Soils at the site were contaminated as a result of the uranium production activities and waste disposal practices of the time. AEC completed decontamination efforts and surveys but as standards and technologies changed over time, U.S. Department of Energy (DOE) performed follow-on investigations to evaluate site conditions in relation to current remediation standards.

Under its authority toexecute FUSRAP, USACE conducted the Remedial Investigation, Baseline Risk Assessment, and Feasibility Study at the Site. The Remedial Investigation determined the nature and extent of FUSRAP contamination while the Baseline Risk Assessment evaluated the risk posed to human health and the environment from the FUSRAP contamination. The Feasibility Study identified Remedial Action Objectives and evaluated remedial action alternatives to address contamination at the FUSRAP areas (as described in Sections H and I). In December 2012, USACE issued a Proposed Plan for public comment, describing the preferred alternative for cleanup of the Site.

USACE identified the FUSRAP-eligible constituents of concern in site soils that were related to the uranium processing activities at the site and that could pose a risk to human health under an industrial land use scenario. Constituents of concern are uranium, thorium, and radium;

specifically Uranium-234 (U-234), Uranium-235 (U-235), Uranium-238 (U-238), Thorium-230 (Th-230), and Radium-226 (Ra-226). The construction worker receptor has been selected as the most conservative receptor group upon which the soil remediation goal or cleanup goal was developed. The remedial action recommended in the Proposed Plan and selected in this Record of Decision only addresses these FUSRAP-eligible constituents of concern and does not address other hazardous contaminants that may be present at the site. Therefore, any other potential hazardous contaminants that may be a result of DuPont’s chemical manufacturing operations are not eligible for a response action under FUSRAP.

Selected Remedy. All remedial alternatives evaluated in the FS are presented in Section II.I, Description of Alternatives. The selected remedy is referred to as Alternative S2, Excavation of Soil and Offsite Disposal combined with Alternative GW3, Monitored Natural Attenuation of residual contaminants in groundwater. Major components of the selected remedy include:

• Excavation of contaminated soil with total uranium concentrations above the remediation goal of 65 picocuries/gram (pCi/g). The remediation goal was determined for the most conservative receptor based on the acceptable dose criterion of 15 millirem per year (mrem/yr) (NJAC 7:28-12.8(a)(1). The remediation goal for total uranium accounts for contributions from the other two constituents of concern – Ra-226 and Th-230.

• Physical separation and management of excavated material containing non-FUSRAP hazardous substances that are commingled with FUSRAP-eligible contaminants. This material may require pretreatment prior to land disposal.

• Transportation of excavated soils by rail to an off-site, permitted disposal facility.

• Recovery of water and non-aqueous phase liquids.

• Performance of a final status survey to verify that the completed remedial action meets the soil remediation goal.

• Implementation of monitored natural attenuation to address residual uranium contamination in groundwater, after completing the soil response action. A defined groundwater monitoring program will be initiated to document the progress and effectiveness of the natural environmental processes (e.g., physical, chemical, biological, and radioactive decay) to decrease residual uranium concentrations in groundwater.

• Evaluation of monitored natural attenuation data during the first five years after implementation to document 1) decreasing trends in uranium concentrations in groundwater over time and to determine if 2) the groundwater remediation goal has been achieved. Based on monitored natural attenuation sampling results, monitoring timeframes would be re-evaluated and refined as necessary. Monitoring would be continued until remedial action objectives have been achieved. The timeframe for achieving remedial action objectives is estimated to be less than 30 years, and may be achievable by the first 5-year review.

• Implementation of land use controls to limit potential onsite exposure to contaminants during remedial action activities. Existing DuPont land use controls and groundwater use restrictions consistent with the property’s industrial land use are key features to this component of the response action.

• Implementation of additional land use controls by USACE will be required in the excavation and surrounding areas consistent with remedial construction operations (e.g., sign postings, road closures, additional security and access restrictions). At the conclusion of these remedial action activities, the land use controls normally imposed by DuPont (or a future property owner) will provide necessary protection to human health or the environment. At that time, no additional land use controls beyond those required by the property owner will be needed.

• A post-remediation dose and risk assessment will be performed to ensure compliance with both the acceptable dose criteria of 15 mrem/yr and acceptable dose criterion under “All Controls Fail” scenario. Under the “All Controls Fail” scenario, the dose associated with the residual contaminant concentrations in groundwater combined with the dose resulted from residual soil contamination at the site must be less than 100 mrem total annual effective dose equivalent, if all institutional and engineering controls failed.

• The remedial action will be considered complete and monitoring will be discontinued when it is determined that compliance has been achieved.

• After two years, in which USACE will demonstrate the effectiveness of monitored natural attenuation in reducing groundwater concentrations, the overall site management would be transferred to DOE for long-term stewardship in accordance with the memorandum of understanding between the DOE and USACE.

The estimated net present value of the Selected Remedy is $39,600,000.

E. Statutory Determinations

The selected remedy, as documented in this Record of Decision, is protective of human health and the environment, complies with State requirements that are applicable or relevant and appropriate, is cost-effective, and utilizes permanent solutions. The New Jersey Administrative Code (NJAC) 7:28-12.8(a)(1) and NJAC 7:28-12.11(e) have been deemed applicable or relevant and appropriate to the remedial action. While the remedy does not satisfy the statutory preference for treatment as a principal element, it does utilize permanent solutions to the maximum extent practicable. Soil removal activities will eliminate the principal threat at the Site and will result in the removal of the source of contamination that currently impacts groundwater and may further impact groundwater if site geochemical conditions change in the future. After the soil remedial action is completed, natural attenuation processes will reduce residual uranium concentrations in groundwater over time. Groundwater monitoring conducted after the Remedial Investigation/Feasibility Study and prior to the Record of Decision has documented decreasing uranium concentrations in groundwater due in part to natural attenuation processes and water table fluctuations.

Five-year reviews, as required, will be conducted in compliance with CERCLA Section 121(c) and the NCP Section 300.430(f)(4)(ii). Five-year reviews will provide the opportunity to evaluate the effectiveness of the remedy and to confirm that land use assumptions have not changed, including site ownership and groundwater use.

F. Record of Decision Data Certification Checklist

The following table provides the location of key remedy selection information contained in Section II, Decision Summary. Additional information can be found in the Administrative Record File for the Site.

Record of Decision Data Checklist Item Record of Decision Section Number Reference

Constituents of concern and their respective concentrations. Section II.E.4

Current and reasonably anticipated future land use assumptions used in the baseline risk assessment and Record of Decision.

Section II.F

Baseline risk represented by the constituents of concern. Section II.G

How source materials constituting principal threats are addressed. Section II.K

Key factors that led to the selection of the remedy. Section II.L.1

Estimated capital, annual operation and maintenance, and the total present worth costs, discount rate, and the number of years over which the remedy cost estimates are projected.

Section II.L.3

Potential land and groundwater use that will be available at the Site as a result of the selected remedy.

Section II.L.4

II. DECISION SUMMARY

The U.S. Army Corps of Engineers (USACE) is addressing residual radiological contamination at specific areas on the DuPont Chambers Works property under the Formerly Utilized Sites Remedial Action Program (FUSRAP). The areas are collectively referred to as the DuPont Chambers Works FUSRAP Site (the Site). This section presents a summary of the USACE’s decisions regarding remediation of impacted soil and groundwater present at the Site.

A. Site Name, Location, and Description

As shown in Figure 1, the DuPont Chambers Works FUSRAP Site is located in Deepwater, Salem County, New Jersey within the property boundaries of the active chemical manufacturing facility owned and operated by E.I. DuPont de Nemours & Company (DuPont). DuPont Chambers Works has operated at this location for more than a century. Located within the Townships of Pennsville and Carneys Point, on the southeastern shore of the Delaware River, north of the Interstate 295 Delaware Memorial Bridge, the facility extends 2.7 miles between the Salem Canal to the south and Helms Cove to the north.

In October 1997, the USACE assumed responsibilities from the U.S. Department of Energy (DOE) as lead agency for remedial actions at the Site. Congress directed this transfer of responsibility for the administration and execution of FUSRAP from DOE to USACE with the FY 1998 Energy and Water Development Appropriations Act, Pub. L.105-62. USACE is addressing the radiological contamination onsite that resulted from past uranium processing activities in support of the nation’s early atomic energy program. In the 1940s, the Manhattan Engineer District (MED) and the Atomic Energy Commission (AEC) contracted with DuPont to process uranium oxides and uranium scrap to produce uranium compounds and a small quantity of uranium metal. These activities conducted for the federal government resulted in areas of radiological contamination at the site.

USACE is utilizing the administrative, procedural, and regulatory provisions 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 § 300.430(f)(2) to guide the FUSRAP investigation and response action (including remedial action) at three operable units (OUs) within the Site. Provisions in the Appropriations Acts for FY 1999 and FY 2000 (Pub. L. 105-245 and 106-60) clarified Congressional intent and required as a matter of law that USACE will conduct cleanup work at FUSRAP sites in accordance with CERCLA and the NCP. Funding is provided on an annual basis by congressional appropriations designated under the Energy and Water Development Appropriations Act.

For simplicity, ‘MED’ will be used to describe the work and activities performed for the federal government in support of the nation’s early atomic energy program whether or not the activities were performed by DuPont under contract to MED and/or AEC. This Record of Decision addresses only the MED-related contamination found in the soil and groundwater within the FUSRAP areas and does not address other potential site contamination resulting from other sources.

B. Site History and Investigations

B.1 Site History

In 1942, MED operations involving uranium began at Chambers Works, 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. Various uranium oxides and uranium-bearing scrap were converted to uranium tetrafluoride, uranium hexafluoride, and uranium metal. No uranium enrichment or depletion processes were conducted at Chambers Works.

In 1948 and 1949, AEC conducted radiological surveys and decontamination of building surfaces consistent with the standard practices at the time. After these activities, AEC released the buildings back to DuPont and MED operations ceased at the site.

B.2 Site Investigations

In the 1970s and 1980s, DOE conducted additional radiation surveys and investigations to evaluate site conditions in relation to current regulatory standards and guidelines. As a result, DOE designated Chambers Works for further investigation and potential cleanup under FUSRAP. The DOE investigations are briefly summarized below and more information may be found in the Sitewide Remedial Investigation Report (USACE 2011b):

• 1977: Oak Ridge National Laboratory (ORNL) conducted a radiation survey of the Chambers Works. Exposure rates in the F Parking Corral (Area of Concern [AOC] 2) were consistent with background radiation levels, while the external gamma radiation levels along the Central Drainage Ditch ( (AOC 3) and the East Area (AOC 6) exceeded background radiation levels (ORNL 1978).

• 1983: Bechtel National, Inc. (BNI) performed a radiation survey of the Chambers Works and found near-surface gamma radiation readings in the F-Corral (AOC 2) were below the average background level, with the exception of one reading. Based upon 19 boreholes, contamination was indicated in layers to a depth greater than nine feet (ft).

Analytical results from two soil samples indicated that uranium-238 (U-238) was the major contaminant with concentrations up to 4,380 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).

• 1998 – Present: After assuming the management and administration of the FUSRAP, USACE initiated site investigations at six AOCs. USACE organized the AOCs into three OUs so that a phased investigation could be conducted. USACE conducted Historical Site Assessment and completed Remedial Investigation for each OU as well as a sitewide groundwater investigation. The Sitewide Remedial Investigation including a Baseline Risk Assessment was compiled and sent to the regulatory agencies in 2009 for review.

The Feasibility Study and Proposed Plan were completed in 2012 after regulatory agency review.

Unrelated to the FUSRAP work, DuPont has been addressing widespread contamination on the property by conducting Resource Conservation and Recovery Act (RCRA) corrective actions.

Since the 1970s, DuPont has operated an extensive sitewide groundwater pump and treat system to address non-FUSRAP chemical contamination in groundwater. The system operates at a rate of 1.5 million gallons per day and treats the pumped groundwater at an onsite wastewater treatment plant. The DuPont system is designed to hydraulically contain contaminants present in the groundwater and would prevent FUSRAP contaminants from migrating offsite, if they were mobile. As part of its RCRA investigation, DuPont has designated the areas of former MED activity as Solid Waste Management Unit (SWMU) 33 but is not addressing corrective actions at these areas while the USACE investigations and response actions are ongoing.

At the conclusion of MED activities at Chambers Works, the standard practice was to demolish the former buildings, and utilize the rubble from these buildings as fill material. Aerial photographic evaluations and interviews performed for USACE helped to determine the probable locations of MED-related building rubble. USACE used this information to identify and investigate the FUSRAP AOCs. Figure 2 shows the location of each FUSRAP OU and AOC with respect to DuPont’s active manufacturing areas, property boundaries, and surrounding area.

• 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.

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

• OU 2 consists of AOC 3, Central Drainage Ditch 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 consists of 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 fluorinated solvents and fluorinated lubricants. MED uranium processing did not take place in the East Area.

B.3 Removal Action for Building Materials

In 1999, USACE conducted a removal action to dispose of structural steel from the former Building 845 (AOC 1). DuPont demolished the former building and stockpiled the steel for subsequent removal and proper disposal offsite. USACE documented the removal action and completed the removal and transport activities in September 1999.

B.4 Post-Remedial Investigation Groundwater Monitoring 2012

Groundwater sampling conducted at the Site (USACE, 2012c) indicated the presence of aqueous uranium but at reduced concentrations than previous monitoring events conducted during the Sitewide Remedial Investigation (2004-2007). The area of the uranium plume decreased by approximately 30% since completion of the Remedial Investigation groundwater measurements.

Radium and thorium concentrations in OU 1 wells remained at background levels, consistent with the earlier groundwater monitoring results.

Aqueous uranium concentrations in AOC 4 and AOC 6 were below the federal drinking water standard in all wells for the first time. The highest total uranium concentration in AOC 4 and AOC 6 was 11.4 µg/L and 9.8 µg/L, respectively. In AOC 6 the aqueous uranium concentrations declined 54% on average from previous maximum results. Radium and thorium concentrations in AOC 4 and AOC 6 wells remained at background levels, as in previous quarters.

C. Community Participation

Community participation activities provide the public with an opportunity to express its views .

USACE, in coordination with the New Jersey Department of Environmental Protection (NJDEP), has involved the community throughout the entire remedial action process. USACE held regular meetings with the community board and interested stakeholders since 1999. On average, two meetings per year were held over the course of the investigation to maintain a dialogue with interested parties and provide opportunities for public input. These efforts resulted in a productive and constructive exchange of information between the USACE, regulatory agencies, local officials, and the public. USACE considered input from the community board and public throughout the Remedial Investigation and Feasibility Study.

USACE released the Proposed Plan for the Site to the public on December 16, 2012. The document was made available to the public in the Administrative Record maintained at the Pennsville Public Library, 190 Broadway, Pennsville, NJ 08070, and at the USACE Philadelphia District or on the District’s website: http://www.nap.usace.army.mil/missions/fusrap. USACE published the notice of availability in local newspapers, the South Jersey Times and the Cumberland Salem County Guide in December 2012 and January 2013. A public meeting was held on Thursday, January 17, 2013 in Pennsville, NJ. At the public meeting, representatives from USACE presented information regarding the MED-related soil and groundwater contamination, remedial alternatives under consideration, and USACE’s preferred cleanup alternative. A public comment period was held from January 17, 2013 through February 18, 2013. USACE responded to all comments received during the comment period. Comments and responses are included in the Responsiveness Summary, Section III of this Record of Decision.

A transcript of the public meeting is available to the public and has been included in the Administrative Record file in the library and on the USACE’s website for the DuPont Chambers Work FUSRAP site.

Community involvement activities have been implemented and updated, as needed, throughout the Remedial Investigation and Feasibility Study to keep the public informed of site activities and to invite community input. USACE developed a public website, maintained the Administrative Record files, published informational materials and public notices, and maintained a project mailing list.

D. Scope and Role of Response Action

The primary objectives of this response action are: (1) to address the OU 1 and AOC 6 soils containing FUSRAP-eligible constituents of concern 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 resources.

Under FUSRAP, the USACE is only authorized to remediate those constituents of concern resulting from past MED activities in support of the nation’s early atomic energy program. At Chambers Works, the only constituents of concern eligible for FUSRAP response are the radioactive isotopes: uranium-234 (U-234), uranium-235 (U-235), uranium-238 (U-238), thorium-230 (Th-230), and radium-226 (Ra-226). Constituents not associated with the uranium refinement processes at Chambers Works may be remediated only if commingled with the above MED-related constituents of concern. If commingled, USACE will remove the non-MED constituents along with FUSRAP-eligible constituents to the extent necessary to accomplish the FUSRAP response action.

The selected remedy combines the excavation and offsite disposal of impacted soils with monitored natural attenuation of groundwater. Land use controls that are designed to limit potential exposure to workers during the remediation period will be used in conjunction with the existing controls imposed by DuPont. Following the soil remedial action, a long term groundwater monitoring program will be implemented to evaluate natural attenuation processes and the reduction of residual aqueous uranium in groundwater. During this time, it is expected that the existing safeguards and controls implemented by DuPont will provide the necessary level of protectiveness for workers consistent with the industrial operations at the Site.

Groundwater sampling results have indicated that radium and thorium are at background levels and uranium concentrations are either stable or decreasing due to natural environmental processes. After the soil removal action, residual concentrations of uranium in groundwater are expected to decrease significantly. The excavation of soil will result in more than 80% removal of the aqueous uranium that is impacting the aquifers in AOCs 1, 2, and 6. Therefore, USACE expects the post remedial action groundwater uranium concentrations to be significantly reduced.

This fact supports USACE’s consideration of monitored natural attenuation as a viable means of addressing residual contaminants in groundwater and improving the quality of the groundwater.

E. Site Characteristics

E.1 Conceptual Site Model

USACE developed the Conceptual Site Model to determine the complete exposure pathways for each receptor scenario, based upon sources of contamination, contaminated media and the pathways of migration as shown in Figure 3. Based upon the Conceptual Site Model, the soil medium was evaluated as the primary source of FUSRAP contamination. The groundwater ingestion pathway was eliminated from evaluation as no receptors utilize the groundwater beneath the Site as a potable water source.

The aquifers beneath Chambers Works are classified as Class IIA groundwater by the State of New Jersey. This classification indicates a designated use, or potential use, as a potable water source using conventional treatment (New Jersey Administrative Code [NJAC] 7:9C). NJDEP has designated Chambers Works as a Classification Exception Area where the designated uses (i.e., potable water source) are temporarily suspended. This classification is tied to the duration of DuPont's New Jersey Pollution Discharge Elimination System discharge to groundwater permit and is re-evaluated every five years at the time of permit renewal. Although Aquifer A is a water bearing zone, it is composed of fill and building rubble/materials and does not support sustained pumping rates of more than two to three gallons per minute in any of the AOCs.

Therefore, Aquifer A was not considered as a viable water producing zone in the Conceptual Site Model and Baseline Risk Assessment. Even though receptors are not using the groundwater as a potable water source, the groundwater ingestion and homegrown garden vegetable ingestion pathways were evaluated for the future residential receptor, using groundwater data collected from the B aquifer. In addition, as part of the chemical risk assessment, inhalation of volatiles from groundwater was considered as a complete exposure pathway under the worker scenario specifically for the utility and construction worker scenarios. The inhalation pathway was not considered complete for the FUSRAP-related radionuclides, which are nonvolatile.

E.2 Surface and Subsurface Features

Chambers Works 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 North American Vertical Datum 1988 (NAVD 88). Elevations are typically 10 ft above

NAVD 88.

A major drainage feature throughout the manufacturing area is the Central Drainage Ditch. The water flow direction of the Central Drainage Ditch is eastward with water depths averaging one to two feet. The Central Drainage Ditch exhibits perennial water flow. Historically, the Central Drainage Ditch connected MED operational areas with the Historical Lagoon A consisting of three settling basins – A, B, and C. Basins A and C are no longer in use and have undergone RCRA closure. The lower half of Basin B is currently being used for site storm-water collection.

The Delaware River is tidal and brackish at Deepwater 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.

Native site soils are alluvial and marsh deposits, but have been substantially modified by landfilling and plant construction activities. Shoreline deposits are sands and silty sands with silty clays. DuPont has gradually expanded Chambers Works by filling in the marsh 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 1993).

The sedimentary deposits beneath Chambers Works can be divided into five major sequences (as defined by DuPont) and which are characterized by aquifers, aquitards, or a combination of the two. An aquifer is an underground, porous layer of sand or rock or group of layers that contain water and can be used as a source of groundwater to supply wells and springs; whereas an aquitard is a water-saturated soil or rock layer that is not capable of transmitting any useful amount of water because of its low permeability:

(1) The A and B aquifers and A-B/B-C aquitards: The A aquifer is the uppermost water-bearing zone at the Chambers Works consisting mostly of fill and construction debris.

The B aquifer consists of sands that are interpreted to be Delaware River alluvium.

These aquifers are not widely developed as a groundwater source in Salem County. The A-B aquitard is discontinuous and thins to zero to the east, as well as in areas where stream channels were once present. The B-C aquitard is a silty clay unit that is several feet thick in OU 1. These aquitards limit movement of water between the A and B aquifers and the deeper water-bearing units.

(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 through the F Aquifer unit: makes up the lowest sedimentary sequence and are the Cretaceous-Age sediments of the Potomac Group.

E.3 Sampling Strategy

From 2002 through 2007, USACE collected environmental samples during a phased, multimedia investigation at each FUSRAP OU. Investigations used historical site information, previous radiological surveys, and the Conceptual Site Model in order to plan the data collection efforts.

To meet the goals of the Remedial Investigation, data collection efforts focused on compiling information regarding surface features, contaminant sources (soil, sediment, and groundwater), surface water and sediments, and groundwater conditions. Samples of soil, sediment, surface water, groundwater, and air were collected and analyzed by onsite and offsite analytical laboratories. Results of these investigations were compiled into a Sitewide Remedial Investigation Report, which is available in the Administrative Record and summarized below.

E.4 Nature and Extent of Contamination

The Remedial Investigation and Baseline Risk Assessment identified site features, assessed the nature and extent of contamination, and evaluated risks to human health and the environment 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: U-234, U-235, U-238, Th-230, and Ra-226. No chemical compounds used in the uranium processing were identified as FUSRAP-eligible contaminants (USACE 2011a).

Onsite soils were investigated, focusing on areas or features known or believed to have been impacted by FUSRAP-eligible constituents. In Appendix A, Tables A-1 through A-4 present a summary of sampling results and statistics for surface soil (Table A-1), soil from all depths (Table A-2), sediment and surface water (Table A-3), and groundwater (Table A-4) for the FUSRAP areas. More detailed information is available in the Final Sitewide Remedial Investigation report (USACE 2011b). As previously mentioned, the Sitewide Remedial Investigation and Baseline Risk Assessment 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.

E.4.1 Soil Contamination

During the Remedial Investigation , soil sampling results for the three FUSRAP operable units were compared against an investigative screening value of 14 pCi/g for total uranium in order to define the nature and extent of MED-related soil contamination. Within OU 1, uranium contamination was detected at depths up to 5.5 ft below ground surface in AOC 1 and to a depth of 11 ft below ground surface in AOC 2. Maximum uranium concentrations in AOC 1 and AOC 2 were reported as 677 pCi/g and 16,584 pCi/g, respectively. Within OU 1, elevated Ra-226 and Th-230 concentrations were identified at locations within or in close proximity to uranium source areas. Collocated with elevated uranium concentrations in OU 1, Ra-226 and Th-230 results in soil range from 0.37 to 2.9 pCi/g, and 0.19 pCi/g to 64 pCi/g, respectively. Figure 4 shows the areas of impacted soil in AOC 1 and AOC 2.

Soils in OU 3, AOC 6, the East Area, were impacted at depths of up to 8 ft below ground surface. The highest concentration of total uranium was 3,910 pCi/g at one ft below ground surface. The total area of soils impacted above the investigative screening value is approximately 4,800 square feet (0.1 acres). More detailed sampling results and discussion of the nature and extent of contamination is provided in the Sitewide Remedial Investigation report, Section 4 (OU 1) and Section 6 (OU 3). Figure 5 shows the areas of impacted soil in AOC 6.

E.4.2 Groundwater Contamination

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 Remedial Investigation report for more detailed groundwater sampling results. Figures 6, 7, and 8 show the areas of impacted groundwater in AOCs 1, 2 and 6 based on groundwater monitoring during the Remedial Investigation. 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. This 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 B/C aquitard in this area. An underlying C Aquifer well has consistently shown uranium levels at background levels. The horizontal extent of B Aquifer uranium-impacted groundwater is limited to approximately 0.2 acres and is located beneath the footprint of the former Building 708.

Groundwater investigations at OU 1 have identified the presence of a light non-aqueous phase liquid. The light nonaqueous phase liquid appears to be coal tar or coal tar distillate. The light nonaqueous phase liquid does not contain uranium above background levels and the coal tar components are not FUSRAP-eligible contaminants.

Only the B aquifer is present in AOC 6. 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. The extent of contaminated groundwater in AOC 6 is shown in Figure 8.

Uranium concentrations exceeded the MCL in one well in AOC 4, (Historical Lagoon Area), with an average of 145 µg/L total uranium 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. The groundwater flow direction in the A Aquifer is towards the river in this area.

However, the monitoring results have consistently shown that the uranium is not migrating towards the river. A slurry wall installed by DuPont is located between this well and the downgradient wells near the river. During the post-Remedial Investigation groundwater monitoring event (Quarter 8, July 2012), all monitoring wells in AOC 4 exhibited groundwater concentrations below 30 µg/L total uranium for the first time. (USACE 2012c)

F. Current and Potential Future Land and Water Uses

F.1 Current Land Use

DuPont Chambers Works is an active chemical manufacturing facility and has been for more than a century. It is currently zoned for industrial use and expected to remain industrial well into the future. The land use directly adjacent to Chambers Works is a mix of recreational (forested/wetlands areas), active industrial, and commercial properties. The residential community of Deepwater is across Shell Road (Route 130) from the front gate. There are no expected changes to current land uses and zoning designations.

F.2 Future Land Use

The reasonably anticipated future land use at Chambers Works is an important consideration in determining the appropriate response action and the extent of the response. The future land use affects the degree of exposures to any residual contamination remaining on the FUSRAP areas.

Expectations of the property owner, community stakeholders, and local planning boards are that the Chambers Works property will remain as an industrially-zoned property well into the future.

This is based on the fact that DuPont has owned and operated the chemical manufacturing facility for more than one hundred years and is addressing widespread chemical contamination on the property. Unrelated to the FUSRAP response, DuPont is conducting long-term remediation plans for soil and groundwater. DuPont, community stakeholders, and USACE expect the chemical manufacturing operations, although reduced in scale over recent years, to continue at the Deepwater, New Jersey location under DuPont ownership. For the purposes of the FUSRAP investigation and remedial action the USACE considers industrial land use as the most reasonable future land use for the Chambers Works property.

F.3 Groundwater and Surface Water Uses

Although the surficial aquifers beneath Chambers Works are not used for drinking water they are designated by the NJDEP as Class II groundwater which could have a potential use as a drinking water source in the future. However, the extensive chemical contamination in groundwater related to historical DuPont manufacturing activities makes that potential use highly unlikely in the foreseeable future. In this area the deeper Potomac Group (F Aquifer) is widely used as a drinking water source in southern NJ and Delaware.

G. Summary of Site Risks

The Baseline Risk Assessment (USACE 2011c), including a Human Health Risk Assessment (HHRA) and a Screening Level Ecological Risk Assessment, was performed for each exposure unit to determine the current and potential future risks to human health and the environment from both radiological and non-radiological chemicals if no remedial action was taken. For evaluation in the Baseline Risk Assessment, the six FUSRAP AOCs were grouped into five separate exposure units based on physical location and receptor exposure patterns. Figure 9 shows the location of the exposure units and Appendix A (Tables A-1 through A-4) presents summary statistics for sampling results by media in each exposure unit. The exposure units include:

• Exposure Unit 1 = AOC 1 and AOC 2 (OU 1)

• Exposure Unit 2A = AOC 3 (OU 2)

• Exposure Unit 2B = AOC 5 (OU 2)

• Exposure Unit 3A = AOC 4 (OU 3)

• Exposure Unit 3B = AOC 6 (OU 3)

This section of the Record of Decision summarizes the results of the Baseline Risk Assessment.

It provides the basis for taking action and identifies the contaminants and exposure pathways that need to be addressed by the remedial action in order to protect human health and the environment.

G.1 Human Health Risk Assessment

USACE evaluated the potential current and future impacts of site contamination on human health if no action is taken at the Site. In the Baseline Risk Assessment, USACE evaluated potential cancer risks and non-cancer health hazards that may result from exposure to both radiological and chemical contamination in the FUSRAP areas. Since both the current and future land use scenarios are industrial, USACE considered four types of workers as the reasonable maximum exposure (RME) receptors. The RME represents the highest level of human exposure that is reasonably expected to occur at the site (USEPA 1989). The RME receptors were an industrial worker (an office worker), construction worker (a remediation worker), maintenance worker, and utility worker. USACE determined that these typical workers in an industrial setting would be exposed to the following exposure pathways – external gamma, inhalation of dust, ingestion of soil and dermal contact with soil. The utility worker will also be exposed to both surface water and sediment. Although not a likely receptor now or in the future, the USACE evaluated a hypothetical residential receptor for comparison purposes. In addition to the exposure pathways noted for the workers, the residential receptor would be exposed to two additional pathways – ingestion of home-grown produce and vegetables and ingestion of groundwater as drinking water. The complete exposure pathways for each receptor scenario are illustrated in Figure 3.

In the Baseline Risk Assessment, USACE utilized both RESidual RADioactivity (RESRAD) computer code, Version 6.3, and USEPA’s Risk Assessment Guidance for Superfund (RAGS) equations to perform the radiological dose and risk assessment (USACE 2011c). RESRAD calculates the total excess cancer risk (i.e., the risk of persons developing cancer as the result of exposure to site contaminants) for four exposure pathways – external gamma, inhalation of dust, ingestion of soil, and incidental ingestion of home-grown produce and vegetables. USEPA’s RAGS equations were utilized to perform dose and risk assessment for exposure pathways involving groundwater, surface water, or sediment (USEPA 1989).

Radiological dose and risks were calculated for each receptor at…