OPERABLE UNIT III
BROOKHAVEN NATIONAL LABORATORY
UPTON, NEW YORK

This record of decision (ROD) presents the selected remedial actions for Operable Unit (OU) III of the Brookhaven National Laboratory (BNL) site in Upton, New York. OU III was developed to address groundwater plumes emanating from the central and southern portion of the BNL site. The selected remedy addresses on and off-site groundwater contaminated with volatile organic compounds (VOCs), and tritium and strontium-90 in groundwater on-site. Thirteen areas of concern (AOCs) located in OU III, four AOCs from other OUs and two Additional Areas of Investigation (AAIs) were investigated and characterized in the Remedial Investigation Report for OU III.

These remedial actions were selected in accordance with the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) as amended by the Superfund Amendments and Reauthorization Act of 1986 (hereinafter jointly referred to as CERCLA), and is consistent, to the extent practicable, with the National Oil and Hazardous Substances Pollution Contingency Plan (National Contingency Plan). This decision is based on the Administrative Record for the BNL site.

The State of New York concurs with the selected remedial actions.

Actual or potential releases of hazardous substances, including chemical and radioactive materials from these areas, may present a threat to public health, welfare or the environment if they are not addressed by implementing the response actions selected in this ROD.

Operable Unit III is one of the six operable units at the BNL site for which remedies have been or will be selected. This ROD documents the selected remedial actions for groundwater contamination in OU III. Removal actions, which are either complete or on going are integrated into the final actions. Completed removal actions and source areas are addressed in Table 2. This ROD documents remedies that are consistent with the overall site cleanup strategy. The ROD includes a description of principal contaminants and their representative risks. Cleanup goals have been established to meet regulatory standards. The clean up objectives are: to meet the drinking water standards in groundwater for VOCs, strontium-90 and tritium; complete the cleanup of the groundwater in a timely manner, which for the Upper Glacial Aquifer goal is 30 years or less; and, prevent or minimize further migration of VOCs, Strontium-90 and tritium in groundwater. Current and future land uses were evaluated in this ROD. The costs of each remedy were estimated and are discussed in the ROD. The best balance of the Environmental Protection Agency's (EPA) remedy selection criteria was used to identify the following selected actions:

Volatile Organic Compounds (VOCs) Remedy: There is a large plume of groundwater contaminated with VOCs in the central and southern portion of the BNL Site and off-site. Several Interim Removal Actions (IRAs) have begun to address VOC contamination, including treatment systems at the southern site boundary and in an off-site, downgradient industrial park. Additionally, public water was provided in a large area south of the BNL Site, to protect public health while the groundwater cleanup is underway.

The selected remedy, Alternative V10c, involves active remediation of both on-site and off-site VOC contamination. It includes the following systems: operation of the on-site and off-site IRAs, including the On-Site Southern Boundary IRA and the Off-Site Industrial Complex IRA; installation of new remedial systems at the Long Island Power Authority (LIPA) right-of-way, North Street, the Brookhaven Airport, downgradient of North Street East, and the eastern portion of the industrial park; and an additional treatment system on-site at Middle Road. The remedy also includes either a new remedial system and/or expansion of the existing on-site pump and treat system to address lower levels of VOCs in the western part of the plume, and a source removal system using re-circulation wells with air stripping treatment near Building 96. Details of the specific number of treatment systems and locations needed to meet the cleanup objectives will be determined during the design process. The period of pumping needed to achieve cleanup objectives will be determined based on monitoring and operating data. Each treatment system will have a monitoring well network which will include downgradient sentry wells. These monitoring well networks will be used to help assess the effectiveness of achieving the clean up objectives. The exact number of monitoring wells will be determined during the design process. The assessment and evaluation of all treatment systems in achieving the clean up objectives will be performed annually. The details of the annual assessment and evaluation will be determined during the design process. If the annual assessments show that the treatment systems are not achieving the clean up objectives then the treatment systems will be modified and/or augmented to ensure that the clean up objectives are being met.

This selected remedy (V10c) is not the one that was proposed in the Proposed Remedial Action Plan (PRAP). The proposed remedy (V10b) did not include the treatment system located on-site for the western low-level VOC plume. The additional system was added in response to community and regulatory concerns about potential impacts to the Carmans River.

If, after source control is complete and effective, the annual assessment indicates that continued operation of the components of the selected remedy is not producing further reductions in the concentrations of contaminants in groundwater, DOE, NYSDEC, and EPA will evaluate whether discontinuance of the remedy is warranted or if modification and/or augmentation of the treatment systems is needed to ensure that the cleanup objectives are met.

Tritium Remedy: A pump and recharge system, which includes three pumping wells located on-site along Princeton Avenue, was installed in May 1997 to extract the tritium contaminated groundwater and discharge it further north to a recharge basin on-site. Pumping at the leading edge of the plume was taken as a precautionary measure to inhibit contaminated groundwater from advancing towards the site's boundary and allow more time for the tritium to decay. A carbon filtration unit also was included in the pump and recharge system to remove VOC's that are also present.

The selected remedy is a modification of alternative T4, as originally proposed in the PRAP. The remedy will combine extraction of groundwater in response to specific contingencies and extensive monitoring and reporting to assure that the cleanup objectives are met. Three specific contingencies were identified in the PRAP, and a fourth has been added in this ROD to address regulatory concerns. Other actions will be evaluated and implemented, as necessary, to ensure that the cleanup objectives are met. Additional monitoring wells will supplement the existing groundwater monitoring network downgradient of the High Flux Beam Reactor's (HFBR) spent fuel pool.

The first and second contingencies were developed to ensure that the tritium plume would migrate no further downgradient above drinking water standards. After an evaluation period established during design of the selected remedy, the tritium pump and recharge system on Princeton Avenue will be put on stand-by and later operated as needed as an integral component of these contingencies. The evaluation period will extend up to a maximum of one year after ROD finalization and will include an analysis of the data against the following two contingency criteria. These two specific contingencies identified are 1) to evaluate the need to reactivate the Princeton Avenue IRA if tritium concentrations exceed 25,000 pCi/l at the Chilled Water Plant Road, and/or 2) reactivate the Princeton Avenue IRA if tritium concentrations exceed 20,000 pCi/l at Weaver Drive.

A third contingency was developed to ensure that if the most concentrated part of the plume were to act as a source of continuing contamination, active remediation would remove this problem. This contingency proposed a low flow extraction system to be installed in the most concentrated area of tritium contamination near the HFBR and activated if concentrations exceed 2,000,000 pCi/l at the front of the reactor. This system then would be used to remove groundwater containing the highest concentrations of tritium from the aquifer. The extracted tritium contaminated water will be disposed of offsite. Technologies to reduce the volume of water that requires off-site disposal may be identified during design. Since the PRAP was issued to the public, groundwater near the HFBR has exceeded 2,000,000 pCi/l. DOE is currently in the process of constructing some of the wells for this low flow extraction system on Cornell Avenue and developing plans to extract the most concentrated part of the plume in front of the HFBR. These extraction wells are scheduled to begin operation no later than three months after execution of this ROD. The detailed operational parameters for this system will be developed during design.

In addition to the ones originally identified in Alternative T4 and proposed in the PRAP, a fourth contingency, an additional low flow extraction system will be installed and operated near Temple Place. This additional system was added in response to regulatory concerns about potential plume migration. The exact location, operational parameters and treatment and disposal options for the extracted water will be developed during design. Operation of the Temple Place extraction system will continue for up to one year. As these extraction wells operate, extensive monitoring will occur to evaluate the effect of extraction locally, as well as on the entire plume. Because of the inherent uncertainties of predicating plume behavior based on groundwater modeling, the actual monitoring data will be evaluated and used to help determine whether continued operation of this extraction system is needed to achieve the cleanup objectives. The criteria to continue system operation beyond one year will be developed during design and based on the attainment of the cleanup objectives.

Strontium-90 Remedy: There are concentrated areas of strontium-90 contamination in the groundwater at three on-site locations: the Chemical Holes Area, the Brookhaven Graphite Research Reactor (BGRR), and the Waste Concentration Facility.

The selected remedy, Alternative S5a, involves installing extraction wells and using ion exchange to remove strontium-90 from the extracted water. Details of the specific number of treatment systems and locations needed to meet the cleanup objectives will be determined during the design process. The period of pumping needed to achieve the cleanup objectives will be determined based on monitoring and operating data. Before implementation of the remedy, a pilot treatability study will be performed to evaluate the effectiveness of extraction and treatment. The final remedy may potentially be modified based on the results of this study. Clean water will be discharged on-site. Residual waste that contains strontium-90 will be disposed of at a licensed facility off-site.

If an assessment and evaluation indicates that continued operation of the components of the selected remedy is not producing further reductions in the concentrations of contaminants in groundwater, DOE, NYSDEC, and EPA will evaluate whether discontinuance of the remedy is warranted or if modification and/or augmentation of the treatment systems is needed to ensure that cleanup objectives are met

Source Areas: Some source areas and soil contaminants are, have been, or will be addressed in other RODS. Thirteen AOCs assigned to OU III were investigated as suspected source areas of groundwater contamination. Also, as the work for OU III was proceeding, groundwater contamination from other OUs and Additional Areas of Investigation (AAIs) was included in the investigation and assessment. Table 1 describes these AOCs and AAIs. Table 2 outlines the actions required for these suspected source areas. Many of the suspected source areas had completed and/or ongoing removal actions and no further action is required. The selected remedy requires a source removal system using re-circulation wells with air stripping treatment near Building 96; excavation and off site disposal of the PCB contaminated soils at Building 96 that are above the New York State cleanup levels; remediation of the groundwater near the Carbon Tetrachloride Tank Spill Area; completion of the Building 830 Underground Storage Tank Removal Action; and management of other suspected source areas as shown in Table 2. The final remedy for potential source areas in AOC-26B (Building 96), such as the anomalies discovered during the geophysical survey, will be documented in a subsequent Record of Decision.

Other Remedy Components: All of the groundwater plumes will require monitoring of new and existing wells and institutional control of the groundwater until completion of remediation. These wells will be located adjacent to the treatment systems and along the downgradient plumes. They will help determine the effectiveness of each treatment system in reducing the concentrations of contaminants over time. Long-term monitoring will also determine the ultimate duration for operation of the treatment systems and will support future decisions to make any changes to the final remedy. At the request of the homeowner, DOE can arrange for monitoring of private wells used for drinking water on properties that previously have declined DOE's offer of public water hookups. In addition, any sale or transfer of BNL property will meet the requirements of CERCLA 120(h) to ensure that future users will not be exposed to unacceptable levels of contamination in the groundwater.

Deferred Decisions: The final remedy for potential source areas in AOC-26B (Building 96), such as the anomalies discovered during the geophysical survey, will be documented in a subsequent Record of Decision. Also, the final remedy for AOC-9D, the Pile Fan Sump, will be documented in the Brookhaven Graphite Research Reactor (BGRR) Record of Decision.

The selected remedies are protective of human health and the environment, comply with federal and state requirements that are legally applicable or relevant and appropriate to the remedial actions, and are cost effective. These remedies utilize permanent solutions and alternative treatment technologies to the maximum extent practicable, and satisfy the statutory preference for remedies that employ treatment that reduces contaminant toxicity, mobility or volume as a principal element.

Should new information become available regarding disposal costs or the cost effectiveness of new technologies during the remedial design or remedial actions that could affect how the remedy selected in this ROD is implemented, the remedy may be modified and documented if such a change does not constitute a fundamental change in the remedy.

A five-year review of the remedial action pursuant to CERCLA §121(c), 42 U.S.C. §9621(c), will be necessary, since some of the selected remedies could result in hazardous substances remaining on site above health-based levels.

George J. Malosh
Manager, Brookhaven Group
U.S. Department of Energy

Robert P. Gordon
Contracting Officer, Brookhaven Group
U.S. Department of Energy

Jeanne Fox
Regional Administrator, Region 2
U.S. Environmental Protection Agency

I. DECLARATION OF THE RECORD OF DECISION

SITE NAME AND LOCATION

STATEMENT OF BASIS AND PURPOSE

ASSESSMENT OF THE SITE

DESCRIPTION OF THE SELECTED REMEDY

DECLARATION

TABLE OF CONTENTS

LIST OF ACRONYMNS

II. DECISION SUMMARY

1. SITE NAME, LOCATION AND DESCRIPTION

2. SITE HISTORY AND ENFORCEMENT ACTIVITIES

2.1 Site History

2.1.1 Previous Actions and Remedial Investigation/ Feasibility Study

2.1.2 History of OU III

2.2 Enforcement Activities

3. HIGHLIGHTS OF COMMUNITY PARTICIPATION

4. SCOPE AND ROLE OF OPERABLE UNIT AND RESPONSE ACTION

5. SUMMARY OF SITE CHARACTERISTICS

5.1 Identification of Contamination

5.2 Soil, Sediment, Groundwater, and Surface Water Investigations

5.2.1 Summary of Investigation of Study Area

5.2.2 Summary of Nature and Extent of Contamination

5.3 Action Summary for OU III

5.3.1 Source Removal

5.3.2 Facility Site Review

5.3.3 Removal Actions and Interim Removal Actions

5.3.4 Current Remedial Action Summary

6. SUMMARY OF SITE RISKS

6.1 Human Health Risks

6.1.1 Identification of Contaminants of Potential Concern

6.1.2 Exposure Assessment

6.1.3 Toxicity Assessment

6.1.4 Human Risk Characterization

6.2 Ecological Risk

6.3 Basis for Response/Remedial Action Objectives

7. DESCRIPTION OF ALTERNATIVES

7.1 Cleanup of VOC Contaminated Groundwater

7.2 Cleanup of Sr-90 Contaminated Groundwater

7.3 Cleanup of Tritium Contaminated Groundwater

8. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

8.1 CERCLA Criteria

8.2 Comparative Analysis

8.2.1 TVOC Comparative Analysis

8.2.2 Strontium Comparative Analysis

8.2.3 Tritium Comparative Analysis

9. SELECTED REMEDIES

10. STATUTORY DETERMINATIONS

10.1 Protection of Human health and the Environment

10.2 Compliance with ARARs

10.3 Cost Effectiveness

10.4 Use of Permanent Solutions and Alternative Treatment Technologies to the Maximum Extent Practicable

10.5 Five-Year Review

III. RESPONSIVENESS SUMMARY

INTRODUCTION

1. RESPONSIVENESS SUMMARY OVERVIEW

Site History

Operable Unit III

Selected Remedial Alternatives for OU III

Level Of Community Support for the Preferred Alternative

Changes to the Proposed Alternative

2. BACKGROUND ON COMMUNITY INVOLVEMENT AND CONCERNS

Community Profile

History of Community Involvement

Summary of Community Participation Activities

3. COMPREHENSIVE SUMMARY OF MAJOR QUESTIONS, COMMENTS, CONCERNS AND DOE RESPONSES

Overview

Summary and Response to Questions and Comments

4. COMMUNITY RELATIONS ACTIVITIES

5. REFERENCES

IV. REFERENCES

V. TABLES

VI. FIGURES

APPENDIX A: COMMENT LETTERS

TABLES

Table 1 - OU III Areas of Concern and Additional Areas of Investigation

Table 2 - Summary of Selected Remedies and Previous Actions

Table 3 - Source Removal Actions

Table 4 - Specific Screening Criteria for Contaminants Exceeding Screening Criteria in any Media in OU III

Table 5 - Detected Concentration Range of the Constituents of Potential Concern in OU III

Table 6 - Exposure Scenarios Evaluated in the Chemical Baseline Human Health Risk Assessment

Table 7 - Exposure Scenarios Evaluated in the Radiological Baseline Human Health Risk Assessment

Table 8 - Non-Carcinogenic Effects: Toxicity Values and Effects of Constituents Of Potential Concern

Table 9 - Carcinogenic Effects: Toxicity Values and Effects of Constituents of Potential Concern

Table 10 - Cancer Risk Slope Factors for Radionuclides of Potential Concern

Table 11 - Chemical Risk Assessment: Cancer Risks and Hazard Indices for Reasonable Maximum Exposure (RME) Scenario

Table 12 - Radiological Risk Assessment: Cancer Risks for Reasonable Maximum Exposure (RME) Scenario

Table 13 - Ecological Constituents of Potential Concern in Environmental Media of OU III

Table 14 - TVOC Remedial Alternatives

Table 15 - Strontium-90 Remedial Alternatives

Table 16 - Tritium Remedial Alternatives

Table 17 - Summary of Comparative Analysis of TVOC Alternatives

Table 18 - Summary of Comparative Analysis of Strontium Alternatives

Table 19 - Summary of Comparative Analysis of Tritium Alternatives

Table 20 - Summary of Estimated Costs

Figure 1 - Regional Site Location Map

Figure 2 - Current Land Use at BNL

Figure 3 - BNL Operable Units

Figure 4 - AOCs and AAIs addressed in this Record of Decision

Figure 5 - Areal Extent of TVOC Contamination in Groundwater

Figure 6 - Areal Extent of Strontium-90 Contamination in Groundwater

Figure 7 - Areal Extent of Tritium Contamination in Groundwater

Figure 8 - Schematic showing the existing Operable Unit III South Boundary Pump-and-Treat System

Figure 9 - Southern Boundary and Industrial Complex Interim Removal Action TVOC Well Locations

Figure 10 - Public Water Hookup Areas

Figure 11 - Tritium Recirculation Flow Schematic of Existing Tritium Interim Removal Action System

Figure 12 - Schematic showing a typical in-well air-stripping system

Figure 13 - Schematic showing strontium-90 ion exchange system

Figure 14 - Areal extent of TVOC, Sr-90 and tritium contamination in groundwater with existing and planned pumping locations

AAI - Additional Areas of Investigation

AGS - Alternating Gradient Synchotron

AOC - Area of Concern

ARAR - Applicable or Relevant and Appropriate Requirement

AS - Air Stripping

ATSDR - Agency for Toxic Substances and Disease Registry

BER - Brookhaven Executive Roundtable

BGRR - Brookhaven Graphite Research Reactor

BHG - Brookhaven Group

BLIP - Brookhaven Linear Isotope Producer

BLS - Below Land Surface

BMRR - Brookhaven Medical Research Reactor

BMSL - Below Mean Sea Level

BNL - Brookhaven National Laboratory

CEDE - Committed Effective Dose Equivalent

CERCLA - Comprehensive Environmental Response Compensation & Liability Act

COPC - Chemicals of Potential Concern

CWF - Chilled Water Facility

DCE - 1,1 dichloroethene

DOE - United States Department of Energy

DOT - Department of Transportation

EE/CA - Engineering Evaluation/Cost Analysis

EDB - Ethylene dibromide

EP - Extraction Procedure

EPA - United States Environmental Protection Agency

ERD - Environmental Restoration Division

ERM - Effects Range Median

ES&HS - Environmental Safety and Health Services

FS - Feasibility Study

GRA - General Response Action

HFBR - High Flux Beam Reactor

HI - Hazard Index

HWMF - Hazardous Waste Management Facility

IAG - Interagency Agreement

ILCR - Individual Lifetime Cancer Risk

IRA - Interim Removal Action

LDL - Low Detection Limit

LINAC - Linear Accelerator

LIPA - Long Island Power Authority

MCL - Maximum Contaminant Level

mg/kg - milligrams per kilogram

NCP - National Contingency Plan

NEPA - National Environmental Policy Act

NPL - National Priorities List

NYCRR - New York State Codes, Rules and Regulations

NYS - New York State

NYSDEC - New York State Department of Environmental Conservation

OU - Operable Unit

PA/SI - Preliminary Assessment/Site Inspection

PCB - Polychlorinated biphenols

PCE - tetrachloroethene

PFS - Pile Fan Sump

PRAP - Proposed Remedial Actin Plan

PRG - Preliminary Remediation Goal

RAO - Remedial Action Objective

RAV - Remedial Action V

RCG - Remedial Capture Goal

RCRA - Resource Conservation and Recovery Act

RESRAD- Residual Radioactive Material Guideline Computer Code

RI - Remedial Investigation

ROD - Record of Decision

RS - Responsiveness Summary

SCDHS - Suffolk County Department of Health Services

SCWA - Suffolk County Water Authority

S&EP - Safety and Environmental Protection Division

SPDES - State Pollutant Discharge Elimination System

STP - Sewage Treatment Plant

SVE - Soil Vapor Extraction

TAL - Target Analyte List

TAGM - NYSDEC Technical Assistance Guidance Memorandum

TBC - To Be Considered

TCA - 1,1,1 trichloroethane

TCE - trichloroethylene

TCL - Target Compound List

TCLP - Toxicity Characteristic Leaching Procedure

TOC - Total Organic Carbon

TPH - Total Petroleum Hydrocarbons

TVOC - Total Volatile Organic Compound

mg/l - micrograms per liter

UST - Underground Storage Tank

VOC - Volatile Organic Compound

WCF - Waste Concentration Facility

Brookhaven National Laboratory (BNL) is a federal facility owned by the U.S. Department of Energy (DOE). BNL conducts research in physical, biomedical and environmental sciences and energy technologies.

BNL is located in Upton, Suffolk County, New York, about 60 miles east of New York City, near the geographic center of Long Island (Figure 1). The following are the distances to neighboring communities from BNL: Patchogue 10 miles west-southwest, Bellport 8 miles southwest, Center Moriches 7 miles southeast, Riverhead, 13 miles east; Wading River, 7 miles north-northeast; and Port Jefferson, 11 miles northwest.

The BNL property, consisting of 5,321 acres, forms an irregular polygon, and each side is approximately 2.5 miles long. Figure 2 is a current land use map of the BNL site. The developed portion of the site includes the principal facilities located near the center of the site, on relatively high ground. They are contained in an area of approximately 900 acres, 500 acres of which were originally developed by the Army. The remaining 400 acres are occupied mostly by various large research machine facilities. Outlying facilities occupy approximately 550 acres and include an apartment area, Biology Field, former Hazardous Waste Management Facility, Sewage Treatment Plant, firebreaks, and the Landfill Areas. The site's terrain is gently rolling, with elevations varying between 40 to 120 feet above sea level. The land lies on the western rim of the shallow Peconic River watershed, with a tributary of the river rising in marshy areas in the northern section of the tract.

The sole source aquifer beneath BNL has three water-bearing units: the moraine and outwash deposits, the Magothy Formation, and the Lloyd Sand Member of the Raritan Formation. These units are hydraulically connected and make up a single zone of saturation with varying physical properties extending from a depth of 45 to 1,500 feet below the land surface. These three water-bearing units are designated as a "sole-source aquifer" by the U.S. Environmental Protection Agency (EPA) and serve as the primary source of drinking-water for Nassau and Suffolk Counties.

To effectively manage remediation of the BNL site, 29 Areas of Concern (AOCs) were identified and divided into discrete groups called Operable Units (OUs), and Removal Actions. The BNL site is divided into six Operable Units (Figure 3).

Figure 4 shows the extent of OU III. It encompasses approximately 50 percent of the total area of the Laboratory. OU III was developed to address groundwater contamination in the central and southern portion of the site and in the off-site areas where groundwater contamination has migrated. Thirteen AOCs assigned to OU III were investigated as suspected source areas of groundwater contamination. Also, as the work for OU III was proceeding, groundwater contamination from other OUs and Additional Areas of Investigation (AAIs) was included in the investigation and assessment. Table 1 describes these AOCs and AAIs.

The BNL site, formerly Camp Upton, was occupied by the U.S. Army during World Wars I and II. Between the wars, the site was operated by the Civilian Conservation Corps. It was transferred to the Atomic Energy Commission in 1947, to the Energy Research and Development Administration in 1975, and to DOE in 1977.

In 1980, the BNL site was placed on New York State's Department of Environmental Conservation (NYSDEC) list of Inactive Hazardous Waste Sites. On December 21, 1989, the BNL site was included on EPA's National Priorities List because of soil and groundwater contamination that resulted from past operations of BNL. Subsequently, the EPA, NYSDEC, and DOE entered into a Federal Facilities Agreement (herein referred to as the IAG) that became effective in May, 1992 (Administrative Docket Number: II-CERCLA-FFA-00201) to coordinate cleanup activities. The IAG identified areas of concern that were grouped into operable units to be evaluated for response actions. The IAG requires a remedial investigation/feasibility study for OU III, pursuant to 42 U.S.C. 9601-9675, to meet the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) requirements. The IAG also requires cleanup actions to address the identified concerns. Cleanup actions at the BNL site will be conducted pursuant to CERCLA, 40 CFR Part 300.

BNL's Final Response Strategy Document (SAIC, 1992) grouped the identified areas of concern into seven operable units. Several operable units were subsequently combined. Remedial investigations and risk assessments were conducted to evaluate the nature and extent of contamination, and potential risks associated with the areas of concern addressed in this Record of Decision. The Operable Unit III Feasibility Study Report (IT, 1999b) was prepared to evaluate the alternatives for remediating the contaminated groundwater addressed in this ROD.

Removal actions and a CERCLA-compliant Remedial Investigation/Feasibility Study (RI/FS) were identified and implemented for OU III. Removal Actions are accelerated actions to prevent, minimize, and mitigate damages to public health or the environment from a release or threatened release and/or be consistent with this final action. Table 2 summarizes these removal actions.

DOE took additional actions in OU III to remove sources of groundwater contamination. These actions include removal of contaminated soils and underground piping and cesspools and septic tanks. These actions are listed in Table 1 where each AOC in OU III is described and are also summarized in Table 3.

The Operable Unit III Remedial Investigation Report (IT, 1999a) includes an evaluation of the nature and extent of contamination, and the human-health and ecological risks associated with the contamination from thirteen AOCs in OU III, and groundwater contamination from four AOCs in OU II/VII. Two additional areas of investigation were characterized.

The Operable Unit III Feasibility Study Report (IT, 1999b) addresses the procedures used in identifying, developing, screening, and evaluating a range of remedial alternatives for the contamination in OU III.

Remedial action alternatives evaluated in the Operable Unit III Feasibility Study Report dealt with on- and off-site groundwater contaminated with VOCs (AOC 15, AOC 24A, AAI 1, and AAI 2), on-site groundwater contaminated with tritium (AOC 29), and on-site groundwater contaminated with strontium (AOC 9, AOC 10, AAI I, and AAI 2). The selected alternatives for groundwater contamination in OU III are described below and summarized in Table 2.

Several interim removal actions already have begun to address VOC contamination as part of the proposed remedy:

• A groundwater treatment system began operation in June 1997 through which VOC contaminated groundwater is extracted at the south boundary and treated by air-stripping. The goal is to prevent additional migration of the contaminated groundwater off the BNL site.
• Another groundwater treatment system began operation in September 1999 along the southern side of the Industrial Complex south of the Laboratory. This system will prevent further migration of the highest concentrations of the deep VOC plume using in-well air stripping.
• Public water was provided to an area south of BNL, and will protect public health while the groundwater cleanup is underway.
• Two underground storage tanks and contaminated soils, which are potential sources of groundwater contamination, have been removed from Building 830.

In addition to these activities, the selected remedy, Alternative V10c, includes a groundwater treatment system at BNL's Middle Road to prevent migration and further contamination of the deeper Magothy Aquifer, and to reduce the duration of remediation in the Upper Glacial Aquifer.

The selected remedy will also include a source removal system using re-circulation wells with air stripping treatment near Building 96. The final remedy for potential source areas in AOC-26B (Building 96), such as the anomalies discovered during the geophysical survey, will be documented in a subsequent Record of Decision. Finally, additional off-site groundwater treatment systems are planned to capture and treat VOCs; they will be located at the Long Island Power Authority (LIPA) right-of-way, North Street, the Brookhaven Airport, downgradient of North Street East, the eastern portion of the Industrial Park and in the western OU III low-level VOC plume. The Feasibility Study estimated approximate numbers and locations of treatment wells. However, details of the specific number of treatment systems and locations needed to meet the performance objective will be determined during the design process.

The exact number of years of active groundwater treatment needed to achieve Remedial Action Objectives will be determined based on monitoring and operating data. If, after source control is complete and effective, monitoring indicates that continued operation of the components of the selected remedy is not producing further reductions in the concentrations of contaminants in ground water, in accordance with the National Contingency Plan, DOE, NYSDEC, and EPA will evaluate whether discontinuance of the remedy is warranted. The criteria for discontinuation will include but not be limited to complete and effective source control, an evaluation of the operating conditions and parameters and a determination that the remedy has attained the feasible limit of contaminant reduction and that further reductions would be impractical.

In addition to the active groundwater treatment systems to remediate the VOCs in groundwater, this alternative requires: monitoring of new and existing wells; completion of the Building 830 Underground Storage Tank Removal Action; management of other potential source areas as shown in Table 2; and institutional control of the on-site groundwater until completion of remediation. At the request of the homeowner, DOE can arrange for monitoring of private wells used for drinking water on properties that previously have declined DOE's offer of public water hookups.

At present, limited characterization has been performed in the Magothy, so additional characterization and installation of groundwater monitoring wells are planned. This work will be done during the design of the remedy, and will be included in the site records. When this characterization and monitoring is completed, the need for a remedy for the Magothy Aquifer, will be evaluated by DOE, EPA and NYS DEC. If a remedy for the Magothy Aquifer is necessary, either this record of Decision will be modified or another decision document will establish the selected action. In either case, the public will have an opportunity to review and comment in accordance with CERCLA.

This selected remedy (V10c) is not the one proposed in the PRAP. The proposed remedy (V10b) did not include the treatment system located on-site for the western low-level VOC plume. The additional system was added in response to community and regulator concerns about potential impacts to the Carmans River.

A pump and recharge system, which includes three pumping wells located on-site along Princeton Avenue, was installed in May 1997 to extract the tritium contaminated groundwater and discharge it further north to a recharge basin on-site. Pumping at the leading edge of the plume was taken as a precautionary measure to inhibit contaminated groundwater from advancing towards the site's boundary and allow more time for the tritium to decay. A carbon filtration unit is included in the pump and recharge system to remove VOCs that are also present in the groundwater.

The selected remedy is a modification of alternative T4, as originally proposed in the PRAP. The remedy will combine extraction of groundwater in response to specific contingencies and extensive monitoring and reporting to assure that the cleanup objectives are met. Three specific contingencies were identified in the PRAP, and a fourth has been added in this ROD to address regulatory concerns. Other actions will be evaluated and implemented, as necessary, to ensure that the cleanup objectives are met. Additional monitoring wells will supplement the existing groundwater monitoring network downgradient of the High Flux Beam Reactor's (HFBR) spent fuel pool.

The first and second contingencies were developed to ensure that the tritium plume would migrate no further downgradient above drinking water standards. After an evaluation period established during design of the selected remedy, the tritium pump and recharge system on Princeton Avenue will be put on stand-by and later operated as needed as an integral component of these contingencies. The evaluation period will extend up to a maximum of one year after ROD finalization and will include an analysis of the data against the following two contingency criteria. These two specific contingencies identified are 1) to evaluate the need to reactivate the Princeton Avenue IRA if tritium concentrations exceed 25,000pCi/l at the Chilled Water Plant Road, and/or 2) reactivate the Princeton Avenue IRA if tritium concentrations exceed 20,000 pCi/l at Weaver Drive.

A third contingency was developed to ensure that if the most concentrated part of the plume were to act as a source of continuing contamination, active remediation would remove this problem. This contingency proposed a low flow extraction system to be installed in the most concentrated area of tritium contamination near the HFBR and activated if concentrations exceed 2,000,000 pCi/l at the front of the reactor. This system then would be used to remove groundwater containing the highest concentrations of tritium from the aquifer. The extracted tritium contaminated water will be disposed of offsite. Technologies to reduce the volume of water that requires off-site disposal may be identified during design. Since the PRAP was issued to the public, groundwater near the HFBR has exceeded 2,000,000 pCi/l. DOE is currently in the process of constructing some of the wells for this low flow extraction system on Cornell Avenue and developing plans to extract the most concentrated part of the plume in front of the HFBR. The detailed operational parameters for this system will be developed during design.

In addition to the ones originally identified in Alternative T4 and proposed in the PRAP, a fourth contingency, an additional low flow extraction system will be installed and operated near Temple Place. This additional system was added in response to regulatory concerns about potential plume migration. The exact location, operational parameters and treatment and disposal options for the extracted water will be developed during design. Operation of the Temple Place extraction system will continue for up to one year. As these extraction wells operate, extensive monitoring will occur to evaluate the effect of extraction locally, as well as on the entire plume. Because of the inherent uncertainties of predicating plume behavior based on groundwater modeling, the actual monitoring data will be evaluated and used to help determine whether continued operation of this extraction system is needed to achieve the cleanup objectives. The criteria to continue system operation beyond one year will be developed during design and based on the attainment of the cleanup objectives.

There are concentrated areas of strontium-90 contamination in the groundwater at three on-site locations: the Glass Holes area, the Brookhaven Graphite Research Reactor (BGRR), and the Waste Concentration Facility. Strontium-90 is a radioactive element with a half-life of 29.1 years.

The selected remedy, Alternative S5a, involves installing extraction wells and using ion exchange to remove the strontium-90 from the extracted water and on-site discharge of the clean water. Details of the specific number of treatment systems and locations needed to meet the cleanup objectives will be determined during the design process. Before implementation of the remedy, a pilot treatability study will be performed to evaluate the effectiveness of extraction and treatment. The final remedy may potentially be modified based on the results of this study. Residuals that contains strontium-90 will be disposed of off-site.

If, after source control is complete and effective, monitoring indicates that continued operation of the components of the selected remedy is not producing further reductions in the concentrations of contaminants in groundwater, in accordance with the NCP, DOE, NYSDEC, and EPA will evaluate whether discontinuance of the remedy is warranted. The criteria for discontinuation will include but not be limited to complete and effective source control, an evaluation of the operating conditions and parameters and a determination that the remedy has attained the feasible limit of contaminant reduction and that further reductions would be impractical.

Table 1 summarizes the AOCs and AAIs in OU III. A summary of inorganic, organic, and radiological contamination of groundwater, soil, and surface water before the Remedial Investigation is given in the Operable Unit III Remedial Investigation/Feasibility Study Work Plan (IT, 1994). More detailed descriptions and references are given in the Operable Unit III Remedial Investigation Report for OU III (IT 1999a).

In 1980, the BNL site was placed on NYSDEC's list of Inactive Hazardous Waste Sites. On December 21, 1989, the BNL site was included on EPA's National Priorities List (NPL). Inclusion on the NPL reflects the relative importance placed by the federal government on ensuring the expedient completion of environmental investigations and the resulting cleanup. Subsequently, the EPA, NYSDEC, and DOE entered into a Federal Facilities Agreement (herein referred to as the InterAgency Agreement; IAG) that became effective in May 1992 (Administrative Docket Number: II-CERCLA-FFA-00201). It identified AOCs to be evaluated for response actions at the BNL site. The IAG requires a Remedial Investigation/Feasibility Study to be conducted for OU III, pursuant to 42 U.S.C. 9601 et. seq., to meet CERCLA requirements. The IAG also requires the conduct of cleanup actions to address identified concerns.

BNL's Final Response Strategy Document (SAIC, 1992) grouped the identified AOCs into seven OUs; several of these were subsequently combined The OUs are in various stages of completion. Remediation at the BNL site will be conducted under CERCLA, 40 CFR Part 300.

After issuing the RODs for the remaining OUs, the necessity of a final assessment from a site-wide perspective will be determined to ensure that the ongoing or planned remedial actions will provide a comprehensive remedy for the BNL site, which is protective of human health and the environment.

A Community Relations Plan was finalized for the BNL site in September, 1991. In accordance with CERCLA Section 113 (k) (2)(B)(I-v) and 117, and the community relations plan, the community relations program focused on public information and involvement. A variety of activities provide information and seek public participation, including a stakeholders mailing list, community meetings, availability sessions, site tours, workshops, and fact sheets. An Administrative Record, documenting the basis for the selection of removal and remedial actions at the BNL site, was established and is maintained at the local libraries listed below. The Administrative Record also includes current site reports, press releases and fact sheets. The following libraries maintain the Administrative Record:

Longwood Public Library
800 Middle Country Road
Middle Island, NY 11953

Mastics-Moriches-Shirley Community Library
301 William Floyd Parkway
Shirley, NY 11967

Brookhaven National Laboratory
Research Library
Bldg. 477A
Upton, NY 11973

The Administrative Record also is kept at EPA's Region II Administrative Records Room, 290 Broadway, New York, NY, 10007-1866.

A public comment period to review the proposed remedy (Proposed Remedial Action Plan, PRAP) and the Final Operable Unit III Remedial Investigation Report and Feasibility Study Report began on March 1, 1999 and was extended through April 30, 1999. A public meeting was held on March 24, 1999 in Berkner Hall at Brookhaven National Laboratory. The Responsiveness Summary section of this document summarizes written and oral comments and DOE responses on the preferred remedial alternatives.

From the comments received during the public-comment period, DOE and BNL believe that the public and local elected officials are in general agreement with the selected remedial alternatives.

During the sixty-day comment period, 28 written comments were received on the OU III documents. The majority of them focused on general concerns, such as the length of time required for cleanup, the length of the comment period, the volume and complexity of material, and the issue of property value. Concern was also voiced about the limited characterization of groundwater in the Magothy Aquifer and the potential for human exposures to VOCs transferred to air in the VOC air stripping treatment processes. Several commentors wanted more specific information on the location of treatment wells and on the location and frequency of monitoring. There was some concern about using natural attenuation as part of the remedy, and some people felt that more active treatment in a shorter time should be undertaken. Several commentors also requested more detailed information on performance standards for the proposed treatment systems.

The Responsiveness Summary summarizes community comments on the preferred remedial alternatives.

In response to requests by stakeholders, the comment period was extended an additional 30 days.

The following modifications were made to the preferred remedial alternative based on regulators' and the public's concerns and input:

• The selected remedy for VOC contamination in groundwater for OU III (V10c) is not the one proposed by DOE in the Proposed Remedial Action Plan (PRAP). The proposed remedy (V10b) did not include the treatment system to be located in the western low-level VOC plume. The additional system was added in response to community and regulator concerns about potential impacts to the Carmans River.

• The selected remedy is a modification of alternative T4, as originally proposed in the PRAP. The remedy will combine extraction of groundwater in response to specific contingencies and extensive monitoring and reporting to assure that the cleanup objectives are met. Three specific contingencies were identified in the PRAP, and a fourth has been added in this ROD to address regulatory concerns. In addition to the ones originally identified in Alternative T4 and proposed in the PRAP, a fourth contingency, an additional low flow extraction system will be installed and operated near Temple Place. This additional system was added in response to regulatory concerns about potential plume migration. In addition to the ones originally identified in Alternative T4 and proposed in the PRAP, a fourth contingency, an additional low flow extraction system will be installed and operated near Temple Place. This additional system was added in response to regulatory concerns about potential plume migration. The exact location, operational parameters and treatment and disposal options for the extracted water will be developed during design. Operation of the Temple Place extraction system will continue for up to one year. As these extraction wells operate, extensive monitoring will occur to evaluate the effect of extraction locally, as well as on the entire plume. Because of the inherent uncertainties of predicating plume behavior based on groundwater modeling, the actual monitoring data will be evaluated and used to help determine whether continued operation of this extraction system is needed to achieve the cleanup objectives. The criteria to continue system operation beyond one year will be developed during design and based on the attainment of the cleanup objectives. Other actions will be evaluated and implemented, as necessary, to ensure that the cleanup objectives are met. Additional monitoring wells will supplement the existing groundwater monitoring network downgradient of the High Flux Beam Reactor's (HFBR) spent fuel pool.

• Community and regulator concerns were raised on the adequacy of the proposed remedy for the Magothy aquifer. As a result of continued input, the proposed remedy for the Magothy aquifer that was contained in the FS/PRAP has been removed from the ROD. Additional characterization and installation of groundwater monitoring wells are planned. After the additional characterization of the Magothy aquifer has been completed the need for a remedy for the Magothy aquifer will be evaluated by DOE, EPA, and the NYS DEC. If a remedy for the Magothy aquifer is necessary, either this Record of Decision will be modified or another decision document will establish the selected action.

• The proposed remedy in the FS/PRAP for Building 96 was air sparging/soil vapor extraction (AS/SVE). Based upon additional technical evaluation, a source removal system using re-circulation wells with air stripping treatment near Building 96 was selected as the preferred remedy for the VOC groundwater contamination for Building 96.

DOE encourages public input to ensure that the preferred remedy for Operable Unit III effectively meets community needs and protects human health and the environment. To ensure early and effective community input into this process, DOE and BNL began reaching out to the community before the Proposed Plan was released. In August and September of 1998, stakeholders were invited to participate in Community Roundtables, and canvassing of residents was conducted. In October 1998, a Community Workshop on OU III cleanup options was held. These activities are summarized in the Final Report on OU III Early Community Input (BNL, 1998c).

Community members had the opportunity to discuss their concerns directly with the BNL and DOE staff. Some of their input was incorporated into the Feasibility Study. For example, stakeholders requested consideration of an option that would complete VOC cleanup faster (in approximately ten years). This alternative was added to the list of those evaluated in the Feasibility Study. Concern was also expressed about the impact of VOCs on the Carmans River, and additional groundwater modeling was done and a new cleanup alternative developed which included possible treatment systems for the western low-level VOC plume. Stakeholder support for leaving the tritium and strontium in the ground rather than extracting it was strong, and this also affected the alternatives recommended for cleanup. This input was used to help develop and evaluate cleanup alternatives in the Feasibility Study.

During the comment period on the Proposed Plan and Feasibility Study, information sessions were held. A public meeting was held on March 24, 1999 in Berkner Hall at Brookhaven National Laboratory. Additional community relations activities included briefings to elected officials and community groups, and articles in the BNL's Environmental Restoration Division's newsletter cleanupdate.

Over 2,300 people are on the BNL mailing list. They receive the newsletter cleanupdate along with frequent mailings about specific remediation activities. Invitations to roundtables, information sessions or public meetings are often included in the mailings. BNL employees and retirees (a combined total of nearly 5,000) also receive cleanupdate and articles in the Brookhaven Bulletin which update them on specific remediation topics. The recently formed Community Advisory Council is another avenue for stakeholder groups to have access to BNL and DOE management and to learn about BNL. While the public continues to be concerned about the contamination that BNL caused and is interested in tracking the progress of cleanup, trust appears to be growing that the contamination is being addressed appropriately.

The Responsiveness Summary gives an overview of all the community relations activities for OU III.

To adequately evaluate BNL's existing and potential environmental problems, and to group these problems into workable units that could be properly scheduled and managed, the 29 AOCs were grouped into six OUs and a number of Removal Actions.

The OU III Remedial Investigation/Feasibility Study, Proposed Plan, and ROD were completed and are in the Administrative Record. Pursuant to the findings documented in the Remedial Investigation/Risk Assessment Report, Feasibility Study, and the Proposed Plan, this ROD addresses remediation of contaminated groundwater in OU III, and documents earlier actions to remediate groundwater, remove cesspools and septic tanks, connect nearby residents to public water supplies and remove sources of groundwater contamination in OU III. Conducting these remedial actions under OU III is part of BNL's overall response strategy, and is expected to be consistent with any planned future actions.

The other OUs are currently in different phases of Remedial Investigation/Feasibility Study, or remedy implementation, and have been or will be addressed in separate RODs.

The main purposes of the Remedial Investigation were to determine the nature, magnitude and extent of contamination from the AOCs included in OU III, those AOCs in OU II/VII that may be associated with groundwater contamination in OU III, and additional areas of investigation, and also to characterize the potential health risks and environmental impacts of any contaminants present. Sampling and analyses conducted during the investigation consisted of geophysical logging, radiological surveys, Geoprobe soil sampling, monitoring well borings, Geoprobe groundwater sampling, monitoring well groundwater sampling, supply well sampling, surface water sampling, and sediment sampling.

Classification of the nature and extent of soil and groundwater contamination was based on screening criteria for chemicals and radiological constituents in the various sample media. Whenever possible, established regulatory criteria, known as chemical specific Applicable or Relevant and Appropriate Requirements (ARARs) were used to screen the analytical data. This was the case for groundwater, where state and/or federal Maximum Contaminant Levels (MCLs) exist for many chemicals. In the absence of ARARs, non-enforceable regulatory guidance values, known as "to be considered" criteria, or "TBCs" were used to screen the data. This was the case for soils, which have no established state or federal ARARs. Radionuclides in soils, for which there are no individual ARAR or TBC concentrations, were screened against site-specific levels calculated using a risk model (Manual for Implementing Residual Radioactive Material Guidelines Using RESRAD (ANL, 1993)) that allowed a dose limit of 15 mrem/year above background. For chemical contamination, State (NYSDEC, 1994a) and EPA (EPA, 1994) soil cleanup guidance was used.

The screening concentrations were used to identify potential contaminant source areas, evaluate contaminant distribution patterns, and assess potential contaminant migration pathways. Table 4 summarizes media-specific screening criteria for contaminants that exceeded any screening criteria in OU III.

The OU III Remedial Investigation (RI) characterized the nature and extent of contamination in OU III's sixteen AOCs and four other identified areas that pose an unacceptable risk to human health and the environment. The field investigation for the OU III RI was conducted from October 1995 through July 1997; sampling and analysis activities consisted of the following:

• Collection and analysis of 76 Geoprobe soil samples for one or more of the following analyses: target compound list (TCL) volatile organic compounds (VOCs), TCL semivolatile organics, TCL pesticides and polychlorinated biphenyls (PCBs), target analyte list (TAL) inorganics, gamma spectroscopy, strontium-89, strontium-90, tritium, isotopic americium and thorium, gross alpha/beta activity, geotechnical parameters, and total organic carbon (TOC).
• Collection and analysis of 406 Geoprobe groundwater samples for one or more of the following analytes: TCL low detection limit (LDL) VOCs, TCL semivolatile organics, TCL pesticides and PCBs, TAL inorganics, filtered TAL inorganics, gamma spectroscopy, LDL gamma spectroscopy, strontium-89, strontium-90, isotopic americium and thorium, tritium, gross alpha/beta activity, europium-154, europium-155, radium 226/228, vanadium-238, plutonium-238, plutonium-239/240, technetium-99, cyanide, filtered cyanide, and TOC.
• Collection and analysis of 123 groundwater samples from monitoring-wells for one or more of the following analytes: TCL VOCs, TCL semivolatile organics, TCL pesticides and PCBs, TAL inorganics, gamma spectroscopy, strontium-89, strontium-90, tritium, gross alpha/beta activity, and cyanide.
• Collection and analysis of four supply-well samples for one or more of the following analytes: TCLVOCs, TCL semivolatile organics, TCL pesticides and PCBs, TAL inorganics, gamma spectroscopy, strontium-89, strontium-90, tritium, gross alpha/beta activity, and cyanide.
• Collection and analysis of three surface-water samples for TCL VOCs, TCL semivolatile organics, TCL pesticides and PCBs, TAL inorganics, gamma spectroscopy, strontium-89, strontium-90, tritium, wet chemistry parameters, and cyanide.
• Collection and analysis of nine surface-sediment samples for TCL VOCs, TCL semivolatile organics, TCL pesticides and PCBs, TAL inorganics, gamma spectroscopy, strontium-89, strontium-90, tritium, gross alpha/beta activity, geotechnical parameters, and TOC.
• Collection and analysis of two sump-water samples for TCL VOCs, gamma spectroscopy, strontium-89, strontium-90, tritium, and gross alpha/beta activity.
• Installation and sampling of 182 temporary wells on-site and off-site.

The data collected during the OU III Remedial Investigation in conjunction with additional screening surveys at BNL, and the HFBR Tritium Plume Investigation were used to assess the nature and extent of contamination in the soils, groundwater, surface water, and sediments in the OU III study area. Significant findings on the types of contaminants identified, potential sources of contamination, and the horizontal and vertical extent of contamination is summarized for each medium in the following sections. Table 4 shows the contaminants identified as being of potential concern (i.e. elevated) based on a comparison to screening levels in each media and area of concern.

To evaluate the nature and extent of contamination in surface soils, samples were taken at the Building 830 Pipe Leak and Underground Storage Tanks, the TCE Spill Area, and the Process Supply Wells and Recharge Basins AOCs. Most inorganic analytes were detected at concentrations either slightly above or below screening concentrations. Thallium and mercury were elevated in samples collected from the Building 830 area. Elevated levels of copper and manganese were detected in the recharge basins in the Process Supply Wells and Recharge Basins AOC. Volatile organic compounds and pesticides were not detected above screening levels in surface soil. PCBs were detected in surface soils above screening levels in the Building 96 area (AOC-26B). Benzo(a)pyrene was the only semi-volatile organic compound detected at a concentration more than twice the screening level, in surface soils from the TCE Spill area. Polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, are commonly encountered in commercial/industrial areas, and can enter the environment in releases from truck and automobile exhausts. Cesium-137 was the only radionuclide with an activity above the screening concentration, in two samples from the Building 830 area. These contaminated soils were removed as part of an OU III Removal Action, using the soil cleanup levels developed under OU I.

Subsurface soil was sampled to determine the horizontal and vertical extent of contamination in OU III. Subsurface soil samples were collected from the Paint Shop, the Building 830 area, the Bubble Chamber Spill Area, the TCE Spill Area, Leaking Sewer Pipes, the Old Firehouse, and the Process Supply Wells and Recharge Basins AOC. The average concentrations of most analytes in the subsurface soils were below the screening concentration. Analytes detected at concentrations above screening levels were manganese, nickel, thallium, benzo(a)pyrene, and cesium-137. Manganese was elevated in subsurface samples from the recharge basins in the Process Supply Wells and Recharge Basins AOC. Nickel was elevated in samples from the Building 830 area and the Bubble Chamber Spill Area. Thallium concentrations were elevated in subsurface soil from the Paint Shop, the Building 830 area, the Bubble Chamber Spill Area, TCE Spill Area, Leaking Sewer Pipes, and the Old Firehouse. Elevated concentrations of benzo(a)pyrene were found in subsurface samples collected from the Old Firehouse. Cesium-137 and Thorium-230 were detected above screening levels in a subsurface sample collected from the area of the Building 830 USTs. These contaminated soils were removed as part of an OU III Removal Action, using soil cleanup levels developed under OU I.

Three recharge basins were sampled as part of OU III: the two basins in AOC 24C, and the recharge basin in the Bubble Chamber Spill Area. There was no evidence of contamination of the Recharge Basins from radioactive wastewater discharges. The basin in the Bubble Chamber Spill Area had elevated levels of copper and benzo(a)pyrene. Iron and copper were elevated in the two basins in AOC 24C. Volatile organics, pesticides and PCBs were not elevated in OU III surface water.

Sediment samples were taken from the recharge basins in AOC 24, an inactive cesspool associated with the Paint Shop, a recharge basin in the Bubble Chamber Spill Area, and recharge basin HT at the North End of the LINAC. Contamination was found only in Recharge Basin HT at the North End of LINAC, with elevated levels of mercury, copper, lead, silver, and zinc. A separate sample contained elevated levels of PAHs and one pesticide, delta-BHC. Radionuclides were not detected in sediments in excess of screening levels. The contamination with petroleum hydrocarbon and pesticides may be related to storm water run-off containing oils and greases from nearby asphalt paved roads and parking lots, and run-off from the LINAC area.

Groundwater sampling was conducted to define the vertical and horizontal extent of contamination in groundwater. The groundwater investigation identified the following plumes of contamination: VOCs (carbon tetrachloride, tetrachloroethene, 1,1,1-trichloroethane, trichloroethene), strontium-90, and tritium.

Volatile Organic Compounds: Carbon tetrachloride was detected at elevated levels in the deep glacial zone (60-150 feet below sea level), in a north-south direction from an area south of Princeton Avenue to an area south of Moriches-Middle Island Road. The carbon tetrachloride plume is approximately 9,500 feet long and up to 900 feet wide. The highest concentrations of carbon tetrachloride, greater than 1,000 ppb, are located between the BNL South Boundary and Carlton Drive. The highest concentration detected to date was approximately 5,100 ppb. The 1,000 ppb plume is approximately 1,500 feet long by 200 feet wide. The exact source of the contamination has not been identified, but it is suspected that it no longer exists. Potential sources for carbon tetrachloride and other contaminants are being evaluated under BNL's Facility Review and PA/SI programs.

Tetrachloroethene (PCE) was found in the vicinity of Building 96 in the water-table zone and in the deep glacial zone near the site boundary. PCE in groundwater samples ranged from 10 to 15,000 ppb. The main source of the PCE is the area immediately south of Building 96, which had been used as a truck-wash station and drum-storage area. In the water-table zone, the PCE plume is approximately 1,600 feet long by 500 feet wide. In the mid-glacial it is about 4,400 feet long by 600 feet wide. There are high concentrations of PCE (greater than 1,000 ppb) in the deep glacial zone from an area north of Princeton Avenue to the southern portion of the Industrial Park.

1,1,1-trichloroethane (TCA) was found in groundwater samples above the MCL of 5 ppb at concentrations ranging from 6 to 1,600 ppb. The two areas with most of the elevated TCA concentrations are the area just south of Building 96 in the middle of the site and the area around the Waste Concentration Facility (WCF) and Alternating Gradient Synchrotron (AGS) in the northern portion of the site. The sources of the elevated levels near the WCF and AGS probably were the cesspools associated with the Bubble Chamber Area. These cesspools contained TCA and were remediated. The TCA in the mid-glacial zone can be described as two types of contamination: high (greater than 50 ppb) and low (less than 50 ppb). The high concentrations occur at three locations between Brookhaven Avenue and South Boundary Road.

Trichloroethene (TCE) was detected in wells above the MCL of 5 ppb at levels ranging from 7 to 27 ppb, primarily in the area between Princeton Avenue and the South Boundary Road.

Because of the similarities of the VOCs found in groundwater in OU III, the horizontal and vertical extent of total volatile organic compounds (TVOC) in groundwater also were assessed. In addition to the data collected as part of the OU III RI, groundwater data were collected for the OU I/IV and for Removal Action V (RA V) located in OU I.

Figure 5 shows the areal extent of Total Volatile Organic Compounds (TVOC) in groundwater. The TVOC contamination extends from the water table to 150 feet below mean sea level. However, the TVOC plume encompasses a larger area, due to the presence of other compounds, such as carbon tetrachloride and TCA. Elevated concentrations of TVOCs are located south of Building 96, in the AGS area, in the Supply and Material Area, and south of the former landfill. TVOCs in groundwater near the AGS and Supply and Material area are being monitored. Further migration of contamination will be prevented by the existing south boundary treatment system and planned systems at Middle Road. Contamination near the former landfill is addressed under Removal Action V. Contamination near Building 96 is addressed under this ROD.

The highest concentrations of TVOC in the mid-glacial zone (greater than 50 ppb) appear as slugs, or discrete areas of contamination, at three locations between Brookhaven Avenue and the South Boundary Road. The high concentration TVOC plume in the deep-glacial zone extends from north of Rowland Street to the downgradient extent of the carbon tetrachloride plume located between Moriches-Middle Island Road and Crestwood Avenue. The deep-glacial plume is approximately 14,000 feet long and up to 2,000 feet wide.

There are two locations of OU I/IV VOC plumes in the mid-glacial zone. The first is on-site, south of Brookhaven Avenue and North of Princeton Avenue; the second is off BNL with elevated concentrations within a localized area along Sleepy Hollow Drive. The Removal Action V (RAV) VOC plume within the mid-glacial zone is located off site just south of the RAV extraction wells. The plume is approximately 3,000 feet long and extends from the Long Island Expressway to the south. The highest concentration of VOCs detected was 258 ppb of TCA.

Strontium-90: Strontium-90 was detected above the MCL of 8 picoCuries per liter (pCi/l) at concentrations ranging from 8.45 to 566 pCi/l. The highest activities (i.e. 566 pCi/l) were observed during the Pile Fan Sump (PFS) groundwater sampling. Most strontium-90 in groundwater is associated with two areas on-site: the Brookhaven Graphite Research Reactor (BGRR), and the Waste Concentration Facility (WCF). There are two distinct strontium-90-contaminated plumes (Figure 6), one around the BGRR, WCF, and PFS, and the other around the Glass Holes.

The plume south of the BGRR is approximately 1,000 feet long and 500 feet wide. The larger of the two Strontium-90 plumes actually is composed of two plumes, the northern half composed of Strontium-90 originating from the WCF and associated tanks and pipelines, and the southern originating from the BGRR Pile Fan Sump area. The larger WCF/Pile Fan Sump Plume is approximately 2,000 feet long and 500 feet wide.

Tritium: Elevated concentrations of tritium were detected downgradient of the High Flux Beam Reactor (HFBR). The source of this tritium was the HFBR Spent Fuel Pool, which was emptied in December 1997. The highest activity was 2,290,000 pCi/l in a monitoring well directly in front of the HFBR (IT, 1999c) ; tritium activity at the downgradient edge of the plume is between 1,000 and 5,000 pCi/l. The tritium plume is located entirely within the boundaries of the Laboratory. The portion of the plume that exceeds the MCL for tritium (20,000 pCi/l) extends approximately 4,500 feet north of BNL's southern boundary at depths from 40 to 150 feet below land surface. The dimensions of the 1,000 pCi/l plume are approximately 3,200 feet long and 625 feet wide. The 20,000 pCi/l plume is approximately 2,600 feet long and 250 feet wide. A second area immediately north of the HFBR stack has tritium concentrations greater than the drinking water. Figure 7 shows the extent of the tritium plume on-site.

Two separate groups of contaminants were identified as potentially of concern in OU III: the groundwater contaminants, and the sediment, soil, and surface-water contaminants. In general, the contaminants in groundwater at OU III are relatively mobile, having moderate to high water-solubility and/or low K_OC values. The majority of the contaminants identified as potentially of concern in soils, sediments, and surface waters at OU III exhibit relatively low- water-solubilities and/or high K_OC values and, therefore, have low leachabilities and low mobilities in groundwater. Also, most of the contaminants detected in near surface areas (i.e., surface soils, surface water) are not highly volatile. Almost all of the contaminants exhibit a strong tendency to adsorb to soil particles and remain relatively immobile in the soils as demonstrated by their high K_OC and K_d values.

The fate of a constituent in the environment is a function of its chemical properties and the physical nature of the site. The potential for environmental transport was examined based on a review of the topographic and hydrogeologic characteristics of the site and a review of the available physical constants and chemical characteristics of each constituent. The most significant fate and transport processes for the study area are summarized below:

• The greatest potential for transport of contaminants at the OU III site is via groundwater transport. Volatile organic compounds, including PCE, TCA, and carbon tetrachloride, have been detected in groundwater plumes indicating their ongoing transport. Also, the radionuclides strontium-90 (which has limited mobility) and tritium (which is mobile and moves with water) were detected in groundwater.
• Volatilization, dust generation, and air transport are considered insignificant based on the extremely limited surface-soil and surface-water contamination.
• Most constituents present in vadose soils and sediments on site are relatively insoluble and have a greater tendency to remain adsorbed. Thus, leaching to groundwater is not expected to be important. Those contaminants considered leachable have already been detected in groundwater.
• From the limited biota expected to occur in the recharge basins or in association with the recharge basins, bioaccumulation of constituents in the food chain is expected to be an insignificant transport pathway.

Several actions have been taken to remove sources of groundwater contamination (Table 3).

Additional actions were taken to remove potential sources of groundwater contamination at other locations on-site; these include the landfills removal action, removal of cesspools and cesspool contents, removal of underground storage-tanks, and replacement of leaking sewer-pipes.

BNL has embarked on an extensive Facility Site Review to identify potential release- points of contaminants from BNL's facilities to the environment. The review began in April 1997 and is an important element of BNL's comprehensive plan to delineate and characterize environmental issues at the site and to develop strategies for cleanup and remediation. The purpose of the project was to review all BNL facilities to identify equipment, operations and activities that have the potential to degrade groundwater. The Facility Site Review categorized facilities as either Priority I or Priority II, based upon previous uses and the age of the facility.

Priority I facilities are those that used or generated significant quantities of radioactive material during the 1950s and 1960s. In addition, facilities that have a history of major programmatic changes during operational periods are considered Priority I facilities. Facilities that do not meet the criteria for Priority I status were designated Priority II.

Twelve Priority I and eight Priority II action items were identified for the Environmental Restoration Division (ERD) during the Facility Site Review. All action items identified in the Facility Site Review will be tracked by representatives of BNL's Environmental Safety and Health Services (ES&HS) until closeout reports have been prepared.

Preliminary Assessment /Site Inspection (PA/SI) investigation were developed to evaluate areas of interest identified in the April 1997 Facility Review. The PA/SI consisted of a field investigation that included collecting and analyzing soil and groundwater samples. The results of this investigation will be used to determine if an identified area should be considered an AOC. Follow-up activities from the Facility Review are continuing.

The following interim removal actions (IRAs) and Removal Actions have been or are being undertaken to immediately reduce concentrations, migration, or exposure to groundwater contaminants:

• On-site OU III Southern Boundary Groundwater Interim Removal Action (IRA): This IRA was implemented in June 1997 in response to the detection of a plume of VOCs in groundwater both on- and off-site. The goal is to prevent additional off-site migration of VOCs in the most concentrated part of the plume at the southern boundary. The IRA consists of a groundwater recovery system at the southern boundary (Figure 8), extraction of groundwater through six wells, and treatment through air-stripping. The clean water then is discharged to a recharge basin. The locations of wells for this pump-and-treat system are shown in Figure 9.
• Off-site OU III Industrial Complex Groundwater Interim Removal Action: This IRA is being implemented to address the off-site migration of the highest concentrations of the deep VOC plume beyond the industrial complex located south of OU III. Its objective is to hydraulically control, extract, and treat groundwater through in-well air-stripping, using an array of seven wells along the southern side of the industrial complex. This interim removal action began in September 1999.
• Off-site Public Water Hookup Interim Action: To ensure protection of the health of the residents located downgradient of OU III and OU I, a residential public-water hookup was established (Figure 10). Public water was provided to homes potentially in the path of contaminated groundwater associated with BNL. Long-term monitoring of groundwater off-site will be conducted.
• Tritium Groundwater Interim Removal Action: This IRA was implemented in response to elevated levels of tritium detected downgradient of the HFBR. It consists of (1) removing of spent fuel from the pool and installation of a stainless steel liner, (2) elimination of potential sources of leakage, and (3) pumping groundwater at the leading edge of the plume. At the time, tritium concentrations were expected to decrease over time and not cross the BNL boundary, three wells were installed along Princeton Avenue as a precautionary measure to extract tritium-contaminated groundwater. The groundwater is treated for chemical contamination by carbon adsorption and discharged to a recharge basin to allow additional time for the tritium to decay. This system began operation in May 1997. A schematic of the re-circulation system is shown in Figure 11.
• Building 830 Underground Storage Tanks Removal Action: This action has removed two out-of-service underground storage tanks, a concrete valve pit, associated piping and contaminated soils and vegetation. The tanks have been removed and the soils have been excavated. Contaminated wastes are in the process of being shipped off site for disposal.
• Interim Removal Action V: This Removal Action addresses on-site groundwater associated with the Current Landfill and former Hazardous Waste Management Facility, both located in OU I. A pump-and-treat system was installed at the south boundary in December 1996 to intercept groundwater containing VOCs migrating from the two source areas and prevent them from moving off-site. The system includes two extraction wells and an air-stripping tower. The clean water is recharged via the RA V recharge basin in the center of the BNL site.
• Carbon Tetrachloride Tank Removal Action. The tank was removed and a removal action is underway to pump-and-treat carbon tetrachloride in groundwater in the immediate vicinity of the former tank.

Based on the results of the OU III RI, the primary concerns associated with the OU III study area are groundwater contamination by VOCs, tritium, and strontium-90. A detailed analysis of alternatives was conducted in the OU III Feasibility Study for onsite groundwater contamination by strontium, on- and off-site groundwater contamination by TVOCs, and on-site groundwater contamination by tritium. Soil contamination with Cesium-137 found in AOC 11/12 (Building 830 Pipe Leak and Tanks) was addressed under an Interim Removal Action.

A baseline risk assessment was done to estimate the human health and ecological risks that could result from exposure to contaminants in OU III if no remediation is performed beyond that accomplished to date. Present and future potential exposures to chemical and radiological contaminants in groundwater, surface water, sediment, soil and subsurface soil were evaluated. The risk assessment is documented in the OU III Remedial Investigation Report (IT, 1999a).

Data collected from the four AAIs were not included in the risk assessment because cleanup actions are underway (Table 2).

A four-step process was used to assess site-related human health risks assuming a reasonable maximum exposure scenario:

• Hazard Identification: identifies the contaminants of concern based upon factors such as toxicity, frequency of occurrence, and concentration.
• Exposure Assessment: estimates the magnitude of actual and/or potential human exposures, their frequency and duration, and exposure pathways (e.g., external exposure from gamma radiation, ingestion of contaminated well water) by which humans could be exposed.
• Toxicity Assessment: determines the types of adverse health effects associated with exposures and the relationship between the magnitude of exposure (dose) and severity of adverse effects (response).
• Risk Characterization: summarizes and combines outputs of the exposure and toxicity assessments to quantitatively assess site-related risks.

Two kinds of human health hazards were addressed in the risk assessment for Operable Unit III: cancer induction and non-carcinogenic toxicity.

Cancer Risk is expressed in terms of the probability that a given human receptor will develop cancer due to estimated exposures over a 70-year lifetime. The current federal acceptable risk range for individual lifetime excess carcinogenic risk is one-in-ten-thousand to one-in-one-million.

Non-carcinogenic effect risks due to Operable Unit III contaminants were estimated by dividing the intake of a chemical by the acceptable intake over the period of exposure. These non-carcinogenic effects are expressed as Hazard Indices (HI). A Hazard Index greater than 1.0 indicates a potential for non-carcinogenic health effects. The maximum acceptable HI is 1.0.

The baseline risk assessment evaluated the health effects that could result from exposure to chemical and radiological contamination in groundwater, surface water, soil and sediment as a result of dermal contact, inhalation, and ingestion associated with current and potential future land uses.

The risk assessment focused on contaminants that are likely to pose significant risks to human health; they are summarized in Table 5. Six inorganic constituents, 16 radionuclides, and 8 organics were identified as chemicals of potential concern.

The baseline risk assessment addressed potential risks to human health by identifying potential pathways by which people may be exposed to contaminants at the site under current and future land-use conditions. Tables 6 and 7 summarize the exposure scenarios evaluated in this baseline risk assessment. The reasonable maximum exposure scenario was evaluated.

The populations exposed under the current land-use scenario were assumed to be on-site industrial workers and an on-site trespasser. The current on-site worker was assumed to perform routine daily activities in OU III, and soil-related exposure pathways were analyzed (inhalation of resuspended soil, incidental ingestion of soil, and dermal contact with soil). Potential exposure of onsite workers or trespassers to subsurface soil was not considered because there is no construction work involving excavation currently in progress in OU III. Occupational exposures to surface water and sediment were not considered since BNL personnel are not routinely exposed to surface water and sediment in the recharge basins during their daily work assignments.

For an older child on-site trespasser, five exposure pathways were evaluated in the current land use exposure assessment: inhalation of resuspended soil; incidental ingestion of soil; direct dermal contact with soil; direct dermal contact with surface water; and, direct dermal contact with sediment. Trespassers were assumed not to ingest surface water or sediment since the recharge basins are too shallow for swimming or wading. The risk assessment for radionuclides did not include the pathways for dermal contact with sediment and surface water because the exposures were orders of magnitude smaller than those for ingestion and inhalation.

Ingestion of on-site groundwater also was not included in the exposure assessment for current use. Wells on-site are constantly monitored for contamination and, if necessary, the groundwater is treated to remove it.

Off-site residences were offered connections to the public-water supply, but a few have elected not to make this connection. The baseline risk assessment evaluated risk to off-site populations from exposure to contaminants in groundwater.

Three hypothetically exposed populations were identified for potential future exposures: a short-term construction worker, an industrial worker, and a resident. The future land use scenario was conservatively assumed to occur after 30 years. The radionuclide risk assessment also estimated risks at 50, 100 and 1000 years.

The short-term construction worker was assumed to be exposed through inhalation of soil particulates and dust, incidental ingestion of soil, and dermal contact with soil. Three soil-related exposure pathways were assumed for the future industrial worker: inhalation of particulates and dust; incidental ingestion of soil; and dermal contact with soil.

Residential exposures were evaluated for both an adult and a young child (age 0-6 years). This conservative scenario assumed that a resident would live on-site for 30 years and use on-site groundwater for all domestic water needs. The exposure pathways were: inhalation of soil; incidental ingestion of soil; dermal contact with soil; ingestion, dermal contact (bathing; chemicals only) and inhalation (showering; chemicals only) of groundwater. Because radionuclides may bioaccumulate in plants and animals, the radiological risk assessment included ingestion of home-grown vegetables and of game and livestock as a potential exposure pathway.

Two human health hazards were addressed in the risk assessment for Operable Unit III: cancer induction and non-carcinogenic toxicity. Tables 8, 9 and 10 summarize the non-carcinogenic and carcinogenic toxicity values for the contaminants of concern.

EPA developed reference doses for indicating the potential for adverse health effects. Reference Doses (RfDs), expressed in units of milligrams/kilogram-day (mg/kg-day), are estimates of daily exposure levels for humans that are thought to be safe over a lifetime.

Cancer slope-factors were developed by EPA for estimating excess lifetime cancer risk associated with exposure to potentially carcinogenic chemicals. Slope factors are expressed in units of (mg/kg-day)^-1.

In the toxicity assessment the toxicological properties of the selected chemicals of potential concern were summarized. Many carcinogenic slope-factors and reference doses were obtained from EPA's Integrated Risk Information System database. Slope-factors and reference doses/concentrations not available in that database were obtained from EPA's second most current source of toxicity information, the Health Effects Assessment Summary Tables. When toxicity values were not available for a specific chemical, the chemical was evaluated qualitatively. Uncertainties related to the chemical toxicity data were also addressed. Some toxicity values in the risk assessment are extremely conservative estimates and include uncertainty factors that may reduce the estimated safe exposure concentrations by up to 1000 times.

Non-carcinogenic risks were assessed using a hazard index (HI) approach, based on a comparison of expected intakes of the contaminant and safe levels of intake (RfD, Reference Doses, Table 8). Estimated intakes of chemicals from environmental media (e.g. the amount of a chemical ingested from contaminated drinking water) are compared to the RfD to derive the hazard quotient for the contaminant in the particular medium. The HI is obtained by adding the hazard quotients for all compounds across all media that impact a particular population. An HI greater than 1.0 indicates that the potential exists for noncarcinogenic health effects to occur from site-related exposures. The HI is a useful reference point for gauging the potential significance of multiple contaminant exposures within a single medium or across media.

Potential carcinogenic risks were evaluated using the cancer slope-factors (Tables 9 and 10) developed by EPA. Slope-factors are multiplied by the estimated intake of a potential carcinogen to generate an upper-bound estimate of the excess lifetime cancer risk associated with exposure to the compound at that level of intake.

For known or suspected carcinogens, EPA considers excess upper-bound individual lifetime cancer risks of between 10^-4 to 10^-6 to be acceptable. This level indicates that an individual has not greater than a one-in-ten-thousand to one-in-one-million chance of developing cancer as a result of site-related exposures to a carcinogen over a 70-year period under specific exposure conditions.

The non-carcinogenic and carcinogenic risks associated with the chemical contaminants of concern at the site that exceed EPA's acceptable levels are summarized in Table 11.

Under current land use, the cumulative carcinogenic risk is 2 x 10^-6 for both an on-site worker and an older child as an on-site trespasser. These risks are within the EPA's acceptable cancer risk range (1 x 10^-4 to 1 x 10^-6). The total cumulative non-carcinogenic hazards to the on-site worker and on-site trespasser were negligible (0.08 and <0.01, respectively) compared to the acceptable HI value of 1.

The carcinogenic risk from carbon tetrachloride to the current adult and young child off-site resident exposed to the maximum concentrations measured in groundwater were 8 x 10^-3 and 4 x 10^-3, respectively. These values exceed the acceptable cancer risk range. The non-carcinogenic health hazard from carbon tetrachloride for the adult and young child off-site resident exposed to the maximum concentrations measured in groundwater were 200 and 470, respectively, both of which exceed EPA guidance levels. TCA is not a human carcinogen and there is no EPA published value for non-carcinogenic risk; thus, the risks associated with current land use exposure cannot be quantitatively estimated for off-site residents. However, the maximum concentration of TCA measured off-site (100 &micro;g/l) is 20 times the maximum contaminant level (5 &micro;g/l). Thus, the presence of TCA and carbon tetrachloride plumes in off-site groundwater could present a public health concern to the few off-site residents who declined access to publicly supplied water.

Under the future land-use conditions, the total chemical carcinogenic risks for a future on-site industrial or construction fell within or below the EPA acceptable risk range of 1 x 10^-4 to 1 x 10^-6, and the acceptable HI of one. The risks to the future residential child and adult were slightly above the EPA's target risk range. This risk is driven by arsenic, for which the risks are over-estimated. The slope factor for arsenic (1.5 mg/kg-day)^-1 is an overestimate. Uncertainties in the study used to derive this value include the likelihood of a non-linear dose-response relationship, problems with exposure estimates, and differences in protein intake levels which may result in a differential susceptibility to arsenic. Several epidemiological studies in the United States have found no association between skin cancer and arsenic in drinking water.

The non-carcinogenic hazard index for the hypothetical future on-site resident adult and young child were estimated to be 3.4 and 8.5, respectively. Ingestion of manganese in groundwater contributed the most hazard to the HI.

Manganese (Mn) is a ubiquitous element that is essential for normal physiologic functioning in all animal species, including humans. The National Research Council recommends a provisional daily dietary Mn intake for adults of 2.0 to 5.0 mg. The EPA established reference dose for Mn is 10 mg/day (0.14 mg/kg-day for a 70-kg adult) for chronic human consumption of Mn in the diet with an uncertainty factor of 3.

If conservative assumptions were made for OU III that a hypothetical future resident uses the groundwater at OU III as the sole water supply and drinks 2 L/day of water from wells, then, based on the 95% UCL of 1,173 &micro;g/L, the Mn intake can be calculated to be 0.034 mg/kg-day. This Mn intake of 0.034 mg/kg-day is much less than the EPA established RfD of 0.14 mg/kg-day for Mn. Even if based on the maximum detected Mn concentration, the calculated Mn intake is 0.195 mg/kg-day, which is only slightly higher than the EPA established reference dose of 0.14 mg/kg-day; this should not be a concern. The reference dose is estimated to be an intake for the general population, including sensitive subpopulations, that is likely to be without an appreciable risk of deleterious effects during a lifetime. In addition, the reported Mn concentrations were obtained from the unfiltered groundwater samples that contain more Mn than the filtered groundwater samples. The filtered groundwater would be more representative of drinking water conditions. Mn in groundwater is, therefore, not considered a concern for human health.

An additional risk assessment was done for the future receptors, assuming exposure to the VOC groundwater plumes identified in OU III (TCA, PCE and carbon tetrachloride). The conservative assumption was made that in the future (30 years) houses would be built near the highest detected concentrations of these on-site plumes, and the residents would use the residential wells as the sole water supply for domestic uses. The risk to a future resident using groundwater at the highest concentration of carbon tetrachloride and PCE exceeds the acceptable risk range. Estimated risks to an adult from exposure to carbon tetrachloride and PCE in groundwater were 6 x 10^-4 and 5 x 10^-3 respectively. Estimated risks to a child from exposure to carbon tetrachloride and PCE in groundwater were 3 x 10^-4 and 2 x 10^-3. Under this highly unlikely scenario, the presence of TCA, PCE and carbon tetrachloride plumes in groundwater on-site could pose a potential health concern for a future resident.

The non-carcinogenic HI for a future on-site residential adult who would be exposed to carbon tetrachloride and PCE at the maximum detected concentrations was estimated to be 14 and 20, respectively. The HI's for the future on-site residential child are 33 and 48. These calculated non-carcinogenic HIs exceed EPA's acceptable HI of 1. TCA risks to a future resident using water from the on-site plumes were not calculated quantitatively because there are no EPA established toxicity values for TCA. However, the maximum concentration of TCA in the on-site plume was 920 &micro;g/l, which is almost 200 times the MCL (5 &micro;g/l). Under this highly unlikely scenario, the presence of TCA, PCE and carbon tetrachloride plumes in groundwater on-site could pose a potential health concern for a future on-site resident.

The carcinogenic risk from carbon tetrachloride for the adult and young child off-site resident exposed to the maximum concentrations measured in groundwater in the future were assumed to be the same as for the current off-site risk assessment (8 x 10^-3 adult, 4 x 10^-3 child). The non-carcinogenic HI's for the future off-site adult and child were 200 and 470, respectively. Thus, the presence of TCA and carbon tetrachloride plumes in off-site groundwater in the future could present a public health concern to the few off-site residents who declined access to publicly supplied water.

Table 12 summarizes the results of the radiological baseline risk assessment for contaminants that exceeded the acceptable risk range.

The radiological risk analyses conducted found that under current land-use conditions, cancer risks for industrial workers at 1, 30 and 50 years from now were 4 x 10^-4, 3 x 10^-4 , and 1 x 10^-4, respectively. These risks are slightly above the acceptable risk range of 1 x 10^-4 to 1 x 10^-6. For the on-site trespasser, risks at 1, 30, and 50 years from now were 4 x 10^-5, 1 x 10^-5, and 6 x 10^-6, which fall below the acceptable risk range. External gamma exposure was the dominant pathway, and the major contributing radionuclides were Cs-137 and Co-60.

The conservative future land-use scenario assumed an on-site resident who was nearly self-sufficient in terms of raising or harvesting a significant portion of their diet from the OU III site. The calculated risk for this unlikely scenario suggests that OU III would pose potential cancer risks slightly above the acceptable risk range to a future on-site population (3 x 10^-4 at year 30 and 1 x 10^-4 at year 50). The major contributing pathway is exposure to external gamma from radionuclides in soil. For the future industrial worker, risk at year 30, is 1 x 10^-4. Risks to industrial workers at years 50 and 100 were below the acceptable risk range. The risk to a short-term construction worker involved in excavation activities in year 30 and beyond was very small (2 x 10^-7 in year 30, 8 x 10^-8 in year 50).

An additional risk assessment was done for the future on-site risk assessment, assuming exposure to the highest concentrations of tritium and strontium-90 measured in groundwater in OU III . The conservative assumption was made that future (30 years) residential houses would be built near the highest detected concentrations of these on-site plumes, and the residents would use the residential wells as the sole water supply for domestic uses. Cancer risks to an on-site resident via the groundwater ingestion pathway for strontium-90 was 1 x 10^-4, and for tritium 2 x 10^-3, which are at or above the acceptable risk range.

Because a few residents off-site elected not to be connected to the public-water supply, the risks to an off-site resident were evaluated. The calculated risk for an off-site resident exceeded EPA's recommended level.

The Ecological Risk Assessment determined whether historical activities at Operable Unit III resulted in levels of chemical and radiological contamination that could adversely affect the ecosystems there.

A standard ecological risk assessment (as prescribed by the EPA) consists of a four-step process used for assessing related ecological risks for a reasonable maximum exposure scenario:

• Problem Formulation: a qualitative evaluation of a contaminant's release, migration, and fate; identification of contaminants of concern, receptors, exposure pathways, and known ecological effects of the contaminants; and, selection of endpoints for further study.
• Exposure Assessment: a quantitative evaluation of the release, migration, and fate of the contaminant; characterization of exposure pathways, and receptors; and measurement or estimation of concentrations at exposure points.
• Ecological Effects Assessment: literature reviews, field studies and toxicity tests linking contaminant concentrations to effects on ecological receptors.
• Risk Characterization: measurement or estimation of current and future adverse effects.

Table 13 shows the potential chemicals of concern for the ecological risk assessment.

Unlike assessments of human-health risk which are concerned with effects on individuals, assessments of ecological risk focus on wildlife population and ecosystem-level effects. Because there is little toxicity data relevant to wildlife, it is difficult to draw inferences at the population-and ecosystems-level. Thus, the ecological assessment for OU III was largely qualitative.

The soil contamination to which terrestrial organisms could be exposed was limited to two small areas: one area at the TCE Soil Area is in a building courtyard that is virtually inaccessible to wildlife, and the other area occupies very limited surface area within the developed portions of OU III at the Building 830 Underground Storage Tank area. Therefore, the exposure of terrestrial wildlife to soil contaminants is insignificant.

From comparing surface-water concentrations in the Recharge Basins to available New York State surface water standards, the screening risk assessment indicated that the most significant potential risks to aquatic communities are due to copper in all three recharge basins investigated (HT at the North End of LINAC, HN01, and HN02). In addition, cadmium concentrations in Recharge basin HN01 were elevated. This analysis is very conservative. The risk was estimated by comparing criteria for dissolved metals to a total measured metal concentration, which will necessarily overestimate risk. In addition, New York State Class D surface water-body standards were used as a screening benchmark. The habitat potential of the recharge basins is very limited due to low water levels, the intermittent presence of water, high temperatures and low dissolved oxygen. Recharge basins are not expected to function as Class D water bodies, and therefore, the risk to aquatic biota is not significant.

The potential risk to the benthic community was most significant in Recharge Basin HT, located at the north end of the LINAC. Mercury, copper, silver and several PAHs were more than an order of magnitude greater than the sediment quality criteria applied. Mercury posed a marginal risk in all other recharge basins. However, the benthic community expected in recharge basins is limited by the habitat. Applying sediment criteria to recharge basins overestimates the risk to the community that could occur there, and risk is expected to be minimal.

Consumption of surface water from the recharge basins by terrestrial animals was also evaluated. Surface water concentrations of contaminants were orders-of-magnitude less than the target species (cottontail rabbit) drinking water no-observed effect level.

Remedial action objectives (RAOs), or "cleanup objectives," are specific goals to protect human health and the environment. These objectives are based on available information standards, such as applicable or relevant and appropriate requirements (ARARs), and risk-based levels established in the risk assessment. After evaluating the nature and extent of contamination in soils, groundwater, surface water, and sediment, and assessing the chemical and radiological risks associated with exposure to contaminants of potential concern, the following RAOs were developed:

• Meet the drinking water standards in groundwater for VOCs, strontium-90 and tritium.
• Complete cleanup of the groundwater in a timely manner. For the Upper Glacial Aquifer, this goal is 30 years or less.
• Prevent or minimize further migration of VOC, Sr-90 and tritium in groundwater.

The selected remedies will prevent further migration of high concentrations of contaminants in groundwater.

If, after source control is complete and effective, monitoring indicates that continued operation of the components of the selected remedy is not producing further reductions in the concentrations of contaminants in ground water, in accordance with the National Contingency Plan, DOE, NYSDEC, and EPA will evaluate whether discontinuance of the remedy is warranted. The criteria for discontinuation will include complete and effective source control, an evaluation of the operating conditions and parameters as well as a determination that the remedy has attained the feasible limit of contaminant reduction and that further reductions would be impractical.

From the results of the Remedial Investigation and Baseline Risk Assessment, it was determined that contaminants in all environmental media, except groundwater, posed minimal risk to human health and the environment. Soil contamination that exceeded screening levels in the Remedial Investigation study did not present important risks to human or ecological health with one exception; the soils contaminated with Cesium-137 at Building 830's underground storage tanks. This soil has been excavated under a Removal Action. It should be noted that many sources of contaminated soil and sediment not included under OU III already have been remediated.

Residents immediately south of the Laboratory were offered a hookup to public water supplies, eliminating the potential source of exposure to, and risk from groundwater contaminants. However, some residents elected not to be connected to public water, or still use well-water for various purposes, like watering a garden and filling a swimming pool. The human-health risk assessment found that VOCs in groundwater could present a public health concern for the few off-site residents who declined publicly supplied water. These homes will be monitored at the request of the homeowner.

The following contaminated groundwater plumes were identified to be of concern:

• On-site groundwater contaminated with strontium;
• On-site groundwater contaminated with tritium; and
• On-site and off-site groundwater contaminated with VOCs.

The remedial action alternatives presented in the Feasibility Study and this Proposal Plan address these plumes. In addition, seven interim removal actions (IRAs) were undertaken to immediately reduce concentrations, impact, migration, or exposure to groundwater contaminants.

The primary contaminants identified in groundwater were carbon tetrachloride, tetrachloroethene, trichloroethane, strontium-90, and tritium. Groundwater contamination in OU III was separated into four areas according to the type and location of contaminants.

These four areas are 1) the on-site TVOC area which includes the TVOC present in the water table and Upper Glacial aquifer on BNL; 2) the off-site TVOC area which includes contamination in the water table, Upper Glacial aquifer, and Magothy aquifer off-site and south of BNL; 3) the strontium-90 contamination in the water-table zone present at the BGRR/WCF and the Glass Holes area; and, 4) the tritium plume in the vicinity of the HFBR.

CERCLA requires that each site remedy be protective of human health and the environment, be cost effective, comply with other statutory laws, and utilize permanent solutions and alternative treatment technologies and resource recovery alternatives to the maximum extent practicable. In addition, the statute includes a preference for using treatment as a principal element for reducing the toxicity, mobility and volume of hazardous substances.

Remedial action alternatives evaluated in the Operable Unit III Feasibility Study Report addressed on-site groundwater contaminated with strontium, on-site groundwater contaminated with tritium, and on- and off-site groundwater contaminated with VOCs. The following alternatives were retained for detailed analysis in the Feasibility Study Report.

Most alternatives to remediate VOCs in groundwater use in-well air-stripping systems or other appropriate technologies in combinations of different locations. Figure 12 is a schematic of a typical in-well air-stripping system. Possible locations for off-site treatment systems include the Long Island Power Authority (LIPA) right of way, North Street, the Eastern Portion of the Industrial Park, and two locations at the northern end of the Brookhaven Airport.

All alternatives (except the No Action Alternative) also assume a groundwater treatment system on the BNL site at Middle Road, and at Building 96, continued operation of the south boundary pump-and-treat system, and completion and operation of the Industrial Park in-well air-stripping system, all of which will help prevent further migration of contaminants into the deeper Magothy Aquifer. All the alternatives rely on natural attenuation to reduce concentrations and include extensive monitoring and modeling of the plume over time.

The number of wells selected for each alternative was based on available characterization and hydrogeological data. The actual number of wells used in the selected alternative will be identified during the design phase. Alternatives investigated in detail to remediate VOCs in groundwater are described below. Table 14 summarizes the costs and time to meet Remedial Action Objectives. Because not all of the alternatives originally identified in the Feasibility Study were evaluated in detail, the alternatives listed below are not all numbered sequentially.

The no action alternative includes no remedial activities for site-wide VOC contamination. In accordance with the National Contingency Plan, the No Action Alternative must be assessed and compared to the other alternatives.

Under this alternative, VOC contamination in groundwater will be remediated through the continued operation of three IRAs: the Southern Boundary IRA treatment system; the Off-site Industrial Complex IRA; and, the Off-site Public Water Hookup Interim Action. This alternative also includes a source removal system using re-circulation wells with air stripping treatment near Building 96. Additional reductions in on- and off-site concentrations of VOCs in groundwater will be achieved through natural attenuation. Natural attenuation occurs when physical, chemical and biological processes reduce the mass, toxicity and mobility of subsurface contamination in a way that reduces risk to human health and the environment to acceptable levels. Installing new monitoring wells, and groundwater monitoring and modeling will be required to evaluate the possibility of impacting potential receptors, such as surface-water bodies, supply wells, and potable wells.

This alternative involves actively remediating on-site and off-site VOC contamination. It includes the on-site systems in alternative V3: the operation of the on-site and off-site IRAs, installation of an in-well air-stripping system at Middle Road and a source removal system in the vicinity of Building 96. This alternative also involves installing in-well air-stripping systems at five locations off-site: the Long Island Power Authority (LIPA) Right-of-Way, Brookhaven Airport, North Street/Sleepy Hollow Drive, near North Street in the OU I RAV plume, and within the western OU III low-level VOC plume. Based on the installation, system operation, modeling, and pre-design data, the specific number of treatment systems and locations needed to meet the performance objective may be modified during the design process. The exact number of years of pumping needed to achieve Remedial Action Objectives will be determined based on monitoring and operating data. Additional monitoring wells are planned and sampling and analysis will be conducted. The goal of this alternative is to reduce further migration of the VOC plume south of the off-site sub-systems.

This alternative includes all the components of Alternative V7, with an additional well in the OUs I/IV Industrial Complex (East) and without the in-well air-stripping wells in the western OU III low-level VOC plume. This alternative involves actively remediating both on-site and off-site VOC contamination. It includes the following on-site systems: operation of the on-site and off-site IRAs, installation of an in-well air-stripping system at Middle Road, and installation of a source-removal system near Building 96. This alternative also involves installing in-well air-stripping systems at five locations off-site: 1 well in the industrial park east, 3 in-well air-stripping well at the LIPA Right-of-Way, 7 wells at Brookhaven Airport, 4 at North Street/Sleepy Hollow Drive, and 1 near North Street in the OU I RAV plume. The goal is to reduce further VOC plume migration south of the off-site sub-systems.

This alternative involves active remediation of both on-site and off-site VOC contamination. It includes the following systems: operation of the on-site and off-site IRAs, including the On-Site Southern Boundary IRA and the Off-Site Industrial Complex IRA; installation of new in-well air stripping systems at the LIPA right-of-way, North Street, the Brookhaven Airport, downgradient of North Street East, the eastern portion of the industrial park; additional treatment systems on-site at Middle Road and in the western OU III low-level VOC plume; and a source removal system using re-circulation wells with air stripping treatment near Building 96. The Brookhaven Airport containment systems, and the OU III and OUI/IV hot spot containment systems will be identical to the Alternatives V10b. The objective of this alternative is to capture and contain the OU III, OUI/IV, and RAV plume in a similar well configuration as alternative V10b in addition to capturing and containing of the western low level VOC plume. The purpose is prevent or reduce the levels at which this low level VOC plume migrates and discharges to the Carmans River. Details of the specific number of treatment systems and locations needed to meet the performance objective will be determined during the design process. The exact number of years of pumping needed to achieve Remedial Action Objectives will be determined based on monitoring and operating data.

This alternative involves active remediation of both on-site and off-site VOC contamination. It includes the following on-site systems: operation of the on-site and off-site IRAs, installation of an in-well air-stripping system at Middle Road, and the installation of a source-removal system near Building 96. This alternative also involves the installation of in-well air-stripping systems off-site: 1 well in the industrial park east, 10 wells at Brookhaven Airport, and 4 at North Street/Sleepy Hollow Drive. The goal is to reduce further migration of the VOC plume south of the off-site sub-systems. This alternative has no treatment at the LIPA right-of-way and, therefore, has more treatment wells located down-gradient at the Airport.

The configuration for this alternative is identical to that of Alternative V10b. Groundwater collected by all the extraction wells will be pumped via piping to a treatment system located on-site, treated by an air-stripper to remove volatiles, and discharged to the OU III basin. This alternative includes the following on-site systems: operation of the on-site and off-site IRAs, installation of extraction wells at Middle Road, and installation of a source-removal system near Building 96. This alternative also involves installing extraction wells at locations off-site: 1 well in the industrial park east, 1 well at the LIPA Right-of-Way, 7 wells at Brookhaven Airport, and 4 at North Street/Sleepy Hollow Drive. The goal is to reduce further VOC-plume migration south of the off-site sub-systems.

Alternatives investigated in detail to remediate strontium-90 in groundwater are described below. Table 15 summarizes the costs and time to meet Remedial Action Objectives. Because not all of the alternatives originally identified in the Feasibility Study were evaluated in detail, the alternatives listed below are not all numbered sequentially.

The no action alternative has no remedial activities. In accordance with the National Contingency Plan, the No Action Alternative must be assessed for comparison to the other alternatives.

Under this alternative, the Sr-90 contamination in the water-table zone near the Brookhaven Graphite Research Reactor, Waste Concentration Facility, and Pile Fan Sump (BGRR/WCF/PFS) is slowly reduced through natural attenuation without any control, removal, treatment, or other mitigating actions. Modeling and monitoring of groundwater is required to evaluate the possibility of impacting potential receptors, such as surface-water bodies, supply-and potable-wells. The monitoring program involves installing new wells to monitor the extent and boundaries of the plumes.

In this innovative alternative, a two step in-situ chemical precipitation process is used to contain the strontium-90 plume. In the first step, solutions containing dissolved phosphate are forced through the groundwater and soil, via injection wells, to react with the strontium contaminants, and convert them to more insoluble compounds. Phosphate salts of strontium are very insoluble. In the second step, solutions of lime are injected into the aquifer. This forms calcium hydroxyapatite (a calcium phosphate), which can co-precipitate or adsorb the strontium. Continued groundwater monitoring would be a part of this alternative.

This alternative includes extracting groundwater from two wells within the BGRR/WCF/PFS plume, and one well downgradient of well 106-16 located south of the Glass Holes area. At each location (BGRR area and Glass Holes area), a system will be installed to treat the using ion-exchange before recharge to an on-site recharge basin. Figure 13 shows a schematic of the proposed Sr-90 ion-exchange system. Ion-exchange resin will be disposed of off-site. The BGRR and WCF pumps would operate for 25 to 30 years and the Glass Holes pumps for 8 years. Continued groundwater monitoring also would be a part of this alternative.

Under this alternative, the WCF/BGRR/PFS strontium plume will be remediated utilizing two extraction wells with groundwater treatment via ion exchange, similar to Alternative S5a. However, the Glass Holes strontium plume remediation will be accomplished using a permeable reactive barrier. The permeable reactive walls will consist of a 3-foot-thick bed of granular clinoptilolite. As the groundwater flows through this zeolite mineral, strontium will be absorbed on the bed. Continued groundwater monitoring would also be a part of this alternative.

Remedial alternatives are being developed for different sections of the tritium plume. Of special interest is the "hot-spot" area of the plume, located along the downgradient edge of the HFBR Building footprint. Several alternatives address containment or removal of this highly contaminated groundwater, including ones that address the leading edge of the 20,000 pCi/l tritium plume.

A tritium Interim Removal Action (IRA) system is operating that recovers approximately 120 gallons per minute from three wells located along Princeton Avenue. The groundwater is treated by carbon adsorption to remove VOCs and discharged to the RA V recharge basin. Because the HFBR spent-fuel pool was emptied, no additional source of tritium exists.

Alternatives investigated in detail to remediate tritium in groundwater are described below, and the costs and time to meet Remedial Action Objectives are summarized in Table 16.

The No Action alternative provides a comparative baseline against which to evaluate other alternatives. Under this alternative, no remedial action will occur and the contamination will be left "as is," without any control, removal, treatment, or other mitigating actions. Long term monitoring and modeling will not be performed for the No Action alternative.

This alternative will consist of natural attenuation with the deactivation of the tritium IRA at Princeton Avenue. Natural attenuation is the process by which concentrations of tritium decrease in the groundwater by diffusion, dilution, and radioactive decay. The natural attenuation process can effectively reduce the contaminant's toxicity, mobility, or volume to levels that are protective of human health and the environment. This option requires groundwater modeling, and evaluating the contaminant's degradation rates and pathways. The primary objective of modeling is to demonstrate that natural processes of decay can reduce concentrations to levels below regulatory standards. Sampling and analyses must be conducted throughout the natural attenuation process to confirm that degradation is proceeding