Operable Unit III Remedial Investigation Report
The Brookhaven National Laboratory (BNL) is a Department of Energy (DOE) laboratory conducting research in physical, biomedical, and environmental sciences, as well as in some energy technologies. Brookhaven Science Associates (BSA), a not-for-profit research management organization, currently operates BNL under contract with DOE.
BNL is located in Suffolk County, Long Island, New York. It is bordered on the west by the William Floyd Parkway, on the east by residential areas and parkland, on the north by residential areas, and on the south by the Long Island Expressway.
In 1980, the BNL site was placed on the Department of Environmental Conservation's (DEC's) list of Inactive Hazardous Waste Disposal Sites. In 1989, the laboratory was included on Environmental Protection Agency's (EPA's) National Priorities List of Superfund sites. BNL's inclusion on both lists was due primarily to the effects of past operations, which posed a potential threat to Long Island's sole source aquifer.
BNL has 29 Areas of Concern (AOCs). To ensure effective management, these areas were grouped into five distinct Operable Units (OUs). Operable Unit III was developed to address site-specific AOCs, concentrating on groundwater plumes originating from the western portion of the site. During the original investigations in 1995 and 1996, the 11 AOCs in Operable Unit III, and the four AOCs located in Operable Unit II/VII, were evaluated with Operable Unit III in terms of their impact on groundwater. Based upon the results of this investigation and the discovery in late 1996 of tritium in groundwater, one additional AOC and four additional areas of investigation (AAIs) were added to the investigation in 1997. The AOCs and four AAIs included in Operable Unit (OU) III are as follows:
- Sub-AOC 15A: Potable and Supply Well Numbers 1, 2, 3, 4, 6, 7, 10, 11, and 12
- Sub-AOC 15B: Monitoring Well 130-02
- Sub-AOC 24A: Process Supply Wells 104 and 105 (groundwater samples collected)
- Sub-AOC 24B: Recharge Basin HP, Medical Center Reactor (soil and sediment samples collected)
- Sub-AOC 24C: Recharge Basin HN, Alternating Gradient Synchrotron (AGS) (surface water and sediment samples collected)
The AOCs not above that only address groundwater have been previously investigated and/or have had sources removed, such that only groundwater remains a potential concern for these AOCs. OU III was developed to address groundwater plumes originating from the western portion of the site. All potential sources there require evaluation for their impact on groundwater. Thus, the AOCs included in OU II/VII were also evaluated in OU III in terms of groundwater impact only. The OU II/VII source investigation was evaluated and presented in the July 1998 OU II/VII Remedial Investigation Report (RI). The OU II/VII AOCs included in this RI to evaluate the impact on groundwater are as follows:
- Sub-AOC 9A: Canal
- Sub-AOC 9B: Underground Duct Work
- Sub-AOC 9C: Spill Sites
- Sub-AOC 10A: Tanks D1, D2, and D3
- Sub-AOC 10B: Underground Pipelines
The aforementioned AOCs were originally investigated in 1995 and 1996. However, based on the results of the investigation and indications of other potential sitewide source areas for groundwater contamination, five AAIs were incorporated into this investigation in 1997. One of these five AAIs (AOC 29 - HFBR Tritium Plume) was upgraded to an AOC and is discussed in this report as a separate AOC. This AOC and the remaining four AAIs are as follows:
The AOCs AAIs (with associated media) listed above were investigated to define the nature and extent of contamination, evaluate potential current and future risks to human health and the environment, and support the development of a comprehensive Feasibility Study (FS) Report. The FS Report will assess proposed remedial actions for all AOCs and associated media that pose an unacceptable risk to human health or the environment. The recommended remedial actions resulting from the FS Report will be documented in the OU III Record of Decision (ROD).
1. Site Description
BNL is located in Upton, Suffolk County, Long Island, New York, approximately 60 miles east of New York City. The site was formerly occupied by the U.S. Army as Camp Upton during World Wars I and II. Between the wars, it was operated by the Civilian Conservation Corps. The site was transferred to the Atomic Energy Commission in 1947, to the Energy Research and Development Administration in 1975, and to the DOE in 1977.
The BNL property is roughly square, approximately 3 miles on each side, encompassing an area of 5,265 acres (approximately 8.22 square miles). The production region includes the principal BNL facilities, which are located near the center of the site on relatively high ground. These facilities comprise an area of approximately 900 acres, of which 500 acres were originally developed by the Army. Outlying facilities occupy approximately 550 acres and include an apartment area, biology field, hazardous waste management facility, sewage treatment plant, and a former landfill area.
2. Additional Source Identification
Even though the primary focus of the OU III RI Report is on contaminated groundwater, additional sources are being investigated. The potential for other unrecognized sources of contamination is of great concern at BNL. Such potential sources will continue to be addressed through the ongoing Preliminary Assessment/Site Inspection Project, Facility Site Reviews, Historical Site Reviews, and review of the Suffolk County Department of Health Services (SCDHS) database. It is BNL's intent to evaluate and/or investigate them. These three ongoing programs are summarized below:
Facility Site Review.
The Facility Site Review is a process to identify any potential release points of contaminants from BNL facilities to the environment. The review began in April 1997, and is an important element of DOE's and BNL's comprehensive plan to further delineate and characterize environmental issues at the site, and to develop future clean-up and remediation strategies. This review was conducted under the auspices of the BNL Directorate, and managed by the Environmental Safety and Health Services Division (ES&HS), formerly the Safety and Environmental Protection Division (S&EP).
The purpose of the project was to review all BNL facilities with the aim of identifying equipment, operations, and activities that have the potential to degrade groundwater. All facilities were included in which operations or activities have been or are being performed that involve hazardous materials, both nuclear and non-nuclear. This process enabled BNL to categorize facilities as either Priority I (higher priority) or Priority II (lower priority), based upon their previous uses and age. All action items identified in the Priority I and Priority II reports have been, and will continue to be, tracked by ES&HS representatives until all closeout reports have been prepared.
A Facility Review Preliminary Assessment/Site Inspection (PA/SI) investigation was developed to address areas of interest identified in the April 1997 Facility Review. The findings are used to determine if an identified area of interest should be considered an AOC. The Facility Review PA/SI consisted of a field investigation, including collecting and analyzing soil and groundwater samples using Geoprobe technology. The 1997 report was distributed by DOE for regulatory review and comment on September 9, 1998. Based upon the data received for the Priority I and II facilities investigated, no AOCs were identified. Although all regulatory comments have not yet been received, some recommendations for additional follow-up sampling were identified and will be addressed during PA/SI FY99 activities.
SCDHS Database Review.
In addition to the Facility Review Process and its associated tracking systems, the Suffolk County Department of Health Services (SCDHS) developed their own database. It represents a set of working notes which summarizes SCDHS issues related to the Facility Review Process that require further explanation or about which the county may have some concerns. There are 1,280 items currently listed in the database and each item is ranked from 1 to 5, where 1 is defined to have known contamination above standards, and 5 is defined as no further action required. Currently, 30 items have a ranking of 1. Approximately 236 items are listed in their database with a rank of 5, leaving approximately 1,014 to be addressed.
The ES&HS, in conjunction with the Environmental Restoration Division (ERD) and Plant Engineering (PE), is in the process of assuring that all items ranked No.1 and No.2 (highest priority) have programs which are is addressing these issues.
Historical Site Review.
In the Fall of 1992, BNL's ERD contracted with IT to perform an Historical Site Review as described in the Interagency Agreement (IAG)-approved January 1991 Work Plan, AHistorical Site Review - Brookhaven National Laboratory Superfund Site@. In July 1993, IT submitted the Historical Site Review Report (HSR) to BNL. The HSR was undertaken to identify Areas of Interest (AOIs) with the potential to become AOCs. Both on-site and off-site information sources were researched and summarized. Based on the findings of the HSR, a second phase study was recommended which would follow up on several specific additional file searches, interview several key employees, and conduct selected field investigations at those AOIs deemed most critical. The recommendations made within the HSR and HSR Follow-up Report were to perform a PA/SI made up of four individual components; a radiological survey, a geophysical survey, a soil-gas vapor sampling and analysis program, and a soil sampling and analysis program. The four individual PA/SI reports are currently being assembled into a PA/SI Report, which is scheduled to be submitted to USDOE, U.S. Environmental Protection Agency (USEPA), and New York State Department of Environmental Conservation (NYSDEC) for review and comment in March 1999.
3. Nature and Extent of Contamination
Preliminary chemical-screening concentrations were developed as baselines for quantifying the horizontal and vertical extent of contamination, if any, in surface soils, subsurface soils, groundwater, surface water, and sediments for the OU III study area. The screening concentrations were used to identify potential contaminants of source areas, evaluate their distribution patterns, and assess their potential migration pathways. Although these screening concentrations were based on regulatory standards, criteria, and guidances, they do not represent remediation goals. Remediation goals are being developed during the Feasibility Study, based on the results of human health and ecological risk assessments and a detailed analysis of applicable or relevant and appropriate requirements.
Surface Soil Contamination.
The surface soil in OU III did not reveal the presence of any significant contamination. Most of the inorganic analytes were detected at concentrations of less than or slightly above the screening/background concentration. Thallium and mercury were detected at elevated levels in the samples collected from the Building 830 Pipe Leak (AOC 11/12). Copper and manganese were detected at elevated concentrations in AOC 24B, the HP Recharge Basin, which indicated that further evaluation may be required. However, based on the risk assessment, exposure to inorganics in soils do not pose an unacceptable risk to human health or the environment.
Volatile organic compounds, pesticides, and polychlorinated biphenyls (PCBs) were not detected at concentrations above the screening levels. For the semivolatile organic compounds, benzo(a)pyrene was the only detected compound at a concentration of more than two times the screening concentration. Specifically, benzo(a)pyrene was detected at such a concentration in two samples collected from the trichloroethene (TCE) Spill Area (AOC 19). Polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, are commonly encountered in industrial/commercial areas. They can enter the environment as releases from forest fires, wood burning, and truck/automobile exhausts.
Cesium-137 was the only radionuclide detected at an activity exceeding the screening concentration; activities of approximately three times the screening level were found in two of the samples collected from AOC 11/12. These activities indicate that cesium-137 in the area of AOC 11/12 may be of concern.
Subsurface Soil Contamination.
The average concentrations of most analytes in subsurface soils for each area of concern were typically below the chemical screening concentration. The only ones that were above screening concentrations and may warrant further study were lead, mercury, manganese, nickel, thallium, benzo(a)pyrene, and cesium-137. However, lead was at an elevated level in only one sample, indicating that it is not a significant concern. The average concentration of nickel in AOC 11/12, was 22.1 mg/kg which is within the range of background nickel concentrations of 0.5 to 25 mg/kg for the eastern United States. Elevated levels of manganese were found only in the Recharge Basins HP. Thallium was consistently detected in the subsurface soil samples at concentrations up to eight times the screening/background concentration. Additionally, the average concentration of thallium detected in each area of concern was greater than the screening/background concentration, suggesting that elevated thallium concentrations are a potential concern. However, exposure to inorganics in the soil was not identified as a concern in the risk assessment.
Benzo(a)pyrene was detected at concentrations of up to six times the screening concentration in the samples collected from the Old Firehouse and the average concentration of benzo(a)pyrene also was greater than the screening level. As mentioned above, benzo(a)pyrene commonly enters the environment as releases from forest fires, wood burning, and truck/automobile exhausts.
Cesium-137 was at an elevated level in one of the subsurface soil samples collected from AOC 11/12. This sample was located proximate to the surface-soil samples that also contained elevated levels of cesium-137, indicating that further evaluation may be warranted in this area.
Four groundwater sampling zones were established to assist in evaluating of the vertical extent of contamination: (1) water table zone, (2) mid-glacial zone, (3) deep glacial zone, and (4) Magothy zone. The water table zone extends from a depth of zero to 50 feet above mean sea level (msl), the mid-glacial zone from zero to 60 feet below msl, the deep glacial zone from 60 to 150 feet below msl, and the Magothy sampling zone from 150 to 250 feet below msl.
Groundwater quality was evaluated based on the analytical results from permanent monitoring wells and GeoprobesJ and geologic interpretations. These data were supplemented by the analytical results from test wells. The primary concerns identified in groundwater were the elevated levels of volatile organic compounds (VOCs), strontium-90, and tritium. Specifically, three primary VOC plumes were identified: (1) carbon tetrachloride in the deep glacial zone; (2) tetrachloroethene (PCE) and 1,1,1-trichloroethene (TCA) contamination extending from the water table zone in the vicinity between Building 96 and Brookhaven Avenue into the deep-glacial zone; and (3) TCA contamination in the water-table zone in the area of the AGS and the Waste Concentration Facility (WCF). The primary source of VOC contamination appears to have been Building 96, which was used as a truck wash station and for drum storage. Since carbon tetrachloride contamination was found only in the deep glacial zone, the source is yet unknown. However, additional investigations are currently being performed under PA/SI, the Facility Site Review, the SCDHS Database Review, and the Historical Site Review.
The carbon tetrachloride plume was found primarily in the deep glacial zone, extend from south of Princeton Avenue to south of Moriches-Middle Island Road. The source of this plume has not been identified; however, as detailed above additional source investigations are currently being performed. An elevated concentration of carbon tetrachloride also was detected in the Magothy zone, however, its vertical extent there is unknown.
The source of the PCE contamination is believed to be the area south of Building 96, which was used as a truck-wash station and, reportedly, a drum storage area/scrapyard. The PCE plume extends from the area south of Building 96 to the South Boundary. Vertically, this plume extends from the water table to approximately 140 feet below msl.
Elevated levels of TCA were frequently detected in the water table zone, centered around the AGS, Building 96, and Building 208. In the mid-glacial zone, high concentrations of TCA were found on Rowland Street, Weaver Street, and south of Princeton Avenue at monitoring well cluster OSC-MW05. TCA contamination in the deep glacial zone was limited to the area at the South Boundary.
Tritium concentration (greater than 20,000 pCi/l) in groundwater extend from the HFBR to just south of Rowland Street. The downgradient edge of the plume, defined by the 1,000 pCi/l contour extends just past Princeton Avenue. The highest tritium activity detected in this plume is 1,590,000 pCi/l; at the downgradient edge of the plume they range between 1,000 and 5,000 pCi/l. A second area with tritium activities greater than the drinking water standard (20,000 pCi/l) is located immediately north of the HFBR Stack.
There are two strontium-90 plumes on site. The first, located south of the BGRR, is approximately 500 feet wide and 1,000 feet long. The second plume actually is composed of two plumes from different source areas. The northern source area is the WCF (Building 811) and associated tanks and pipelines; the second is the Building 801 Pile Fan Sump. The WCF/Building 801 PFS plume is approximately 500 feet wide and 2,000 feet long, extending in a north-south direction from the WCF to Cornell Avenue.
Isolated areas of gross beta, radium-226, strontium-90 and inorganic contamination also were identified. Elevated concentrations of inorganics, primarily lead, which may warrant further evaluations were detected between the Bubble Chamber and the north end of the LINAC. However, semivolatile organic compounds, pesticides, and PCBs were not identified as a concern in the groundwater in the OU III study area.
Surface Water Contamination.
Three recharge basins were sampled as part of OU III: Recharge Basin HZ in AOC 14, and the two Recharge Basins HN in sub-AOC 24C. Recharge Basin HZ receives runoff from the northern portion of AOC 14 via a ditch. Several polycyclic aromatic hydrocarbons were detected in its surface water, which may be related to local truck/automobile traffic. However, only one polyaromatic hydrocarbon (PAH), benzo(a)pyrene, exceeded screening criteria. Storm water runoff from local roads and parking lots contains oil and grease which may be a source of semivolatile contamination in surface water samples. Recharge Basins HN are located within the Relative Heavy Ion Collider (RHIC) ring and received non-contact cooling water from the AGS. There is no evidence of contamination of the recharge basins from radioactive wastewater discharges; however, iron and copper were at elevated levels. Iron was approximately twice the screening criteria in both basins, and copper concentrations were eight to nine times the screening level in all three surface water samples.
Nine sediment samples were collected from one inactive cesspool and seven recharge basins as follows: one sample from Recharge Basin HZ in AOC 14, three samples from Recharge Basin HT in AOC 20, one sample each from the two Recharge Basins HP in sub-AOC 24B, one sample each from the two Recharge Basins HN in sub-AOC 24C, and one sample from an inactive cesspool in AOC 7. Except for samples collected from Recharge Basin HT, all sediment samples contained analytes having concentrations of less than two times the screening level. Mercury concentrations in two samples collected from basins HT were approximately 6 to 10 times the screening concentration of 0.71 mg/kg. In addition, these two samples contained elevated levels of copper, lead, silver, and zinc. These two samples were collected from a location away from the outfall of Recharge Basin HT. Although the sediment sample collected near the outfall of Recharge Basin HT did not contain inorganic contamination, it did have contain elevated levels of PAHs and one pesticide, delta-benzene hexachloride (BHC). Recharge Basin HT receives runoff from the LINAC area that contains contaminated landscaping soils. Storm water runoff from local roads and parking lots contains oil and grease which may be the source of semi-volatile contamination in sediment samples. Contaminants within Recharge Basin HT may be related to these sources.
5. Baseline Human Health Risk Assessment
A baseline human health risk assessment was conducted to estimate the potential carcinogenic risks and non-carcinogenic health hazards to current and future human populations resulting from exposure to chemical and radiological constituents originating from BNL OU III, assuming that a remedial action was not implemented. The analytical data used were from samples collected from October 1995 through August 22, 1997. In addition, for the radiological risk assessment, the analytical data from the Brookhaven Graphite Research Reactor (BGRR) samples collected from October to December 1997 were included. This baseline assessment was designed to provide a conservative estimate of potential risks and health hazards to sensitive subpopulations in the absence of any remedial action at the site. Therefore, all these risk estimates are upper-bound or maximum estimates of potential health risks.
A conservative groundwater plume risk assessment was also made to assess the potential risks posed to current off-site residents and future on-site residents via groundwater ingestion, the dominant groundwater exposure pathway. The purpose of this assessment was to conservatively evaluate the potential risks to potential receptors who would be exposed to the maximum detected concentrations of the primary contaminants associated with the identified on-site and off-site groundwater plumes. Off-site residents were offered hookups to the public water supply; however, a few residents (<1%) have selected not to be connected. A highly conservative hypothetical scenario for a future resident also was included in this assessment which assumes that this resident would live at the highest concentrated point of the groundwater plumes and would use well water as the sole domestic water supply.
Chemical Risk Assessment.
Under the current land-use conditions, the cumulative carcinogenic risk is 2 x 10-6 and 3 x 10-6, respectively, for on-site worker and older child (aged 12-17) as an on-site trespasser at OU III. These risks are within the USEPA's current recommended target range for carcinogenic risk (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). The current USEPA's recommended non-carcinogenic target value is unity (1).
Two groundwater plumes were characterized off site. The primary contaminants associated with them were carbon tetrachloride and TCA. The carcinogenic risk and non-carcinogenic health hazard for carbon tetrachloride to the off-site resident exposed to the maximum concentrations of the groundwater contaminants are estimated to be 8 x 10-3 and 200, respectively, which exceed the USEPA's recommended risk guidance levels. TCA is not a human carcinogen, and there is no USEPA published toxicity value for non-carcinogenic risk; thus, the risks due to exposure cannot be quantitatively estimated for off-site residents. However, the maximum concentration of TCA (100 ppb) detected in the off-site groundwater is 20 times the maximum contaminant level (MCL) of 5 ppb. Thus, the presence of the TCA and carbon tetrachloride plumes in the off-site groundwater could present a potential health concern to the small population of off-site residents who chose not to be hooked up with the public water supply.
Under potential future land-use conditions, the risks to a future on-site worker and a construction worker fell within or below the USEPA target risk range of 1 x 10-4 - 1 x 10-6 and the health hazard target value of one. The risks to the future residential adult and child were slightly above the USEPA's target risk range. The non-carcinogenic hazard index for the hypothetical future residential adult and young child are estimated to be 3.27 and 8.49, respectively, which are above the current USEPA's target level. Exposure by groundwater ingestion was the predominant pathway contributing the most non-carcinogenic hazard to the total hazard index.
For the on-site groundwater plume risk assessment, the on-site VOC groundwater plumes identified at OU III are TCA, PCE, and carbon tetrachloride plumes. The risks to a future resident who would live directly at the highest concentrated point of the carbon tetrachloride and PCE plumes via groundwater ingestion are above the USEPA's recommended risk threshold. Similar to the off-site groundwater plume risk assessment, the TCA risks to the future resident were not calculated quantitatively because there are no USEPA established toxicity values. However, the maximum concentration of TCA detected in the on-site groundwater plume was 920 ppb, which is almost 200-fold of the MCL of TCA (5 ppb). Thus, under this highly unlikely and conservative scenario, the presence of the TCA, PCE and carbon tetrachloride plumes in the on-site groundwater could pose a potential health concern to this hypothetical future resident.
Radiological Risk Assessment.
The radiological risk assessment was performed using the DOE-approved and validated residual radioactivity computer code (RESRAD version 5.82) developed by Argonne National Laboratory. The exposure pathways evaluated were similar to those used for the chemical risk assessment and incorporated exposure through inhalation, ingestion, and external gamma exposure from radiologically contaminated soils, sediments, surface water, and groundwater. Risks were calculated for current on-site workers, trespassers, and off-site residents, and for future residents, industrial workers, construction workers and residents, assuming 30 years of institutional controls before the site was released for public use. Similar to the chemical risk assessment, a radiological groundwater plume risk assessment was also conducted. The two radiological groundwater plumes characterized on-site were strontium-90 and tritium plumes; there were no radionuclide groundwater plumes characterized off site.
The baseline radiological risk assessment shows that under current land-use conditions, the 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 or at the current USEPA's target acceptable risk range of 1 x 10-4 to 1 x 10-6. For the on-site trespasser, the risks were estimated to be 4 x 10-5, 1 x 10-5, and 6 x 10-6, which fell below USEPA guidance level. The external gamma exposure was the dominant pathway, and the major contributing radionuclides were cesium-137 and cobalt-60.
A conservative health protective scenario, selected to fully assess radiological risks, evaluated an on-site resident at OU III following a loss of institutional control after 30 years. This residential scenario evaluated multiple exposure pathways to all environmental media, including the use of groundwater as a source of potable water, and the consumption of home-grown fruits and vegetables, and game (e.g., deer meat) as significant portions of the human diet. A short-term construction worker involved in excavation also was selected to evaluate radiologic risks associated with sub-surface soil. The total risk to the construction (excavation) worker in year 30 and beyond was negligible (2 x 10-7 at year 30 and 8 x 10-8 at year 50).
For the potential future residents, the risk for year 30 is 3 x 10-4, which is slightly above USEPA guidance for target carcinogenic risk, and 1 x 10-4 at year 50, which is at USEPA's guidance. The major contributing pathway is exposure to external gamma radiation from radionuclides in the soil. Cesium-137 is the major contributor in both the cases.
For the future industrial worker, the risks at year 30 is 1 x 10-4, which is at the USEPA guidance for target carcinogenic risk. At years 50 and 100, the risks to the industrial workers were below the USEPA guidance level.
The groundwater plume risk assessment was performed for strontium-90 and tritium, the two major contaminants associated with the two on-site groundwater plumes. The purpose was to conservatively assess the potential risk to on-site residents who would build a house on the highest concentrations of these two groundwater plumes, and would use well water as the sole domestic water supply. The maximum detected concentrations of strontium-90 and tritium are 146 and 1,590,000 pCi/l which are 18 and 80 fold of the respective MCLs (8 pCi/l for Sr-90 and 20,000 pCi/l for tritium). Although the chemical toxic effects of strontium and tritium are relatively low, the radiation hazard of these two radionuclides to human health may be of concern. The risks of exposure to strontium-90 and tritium continuously for 30 years to these maximum detected concentrations to a highly unlikely future on-site resident drinking groundwater are calculated to be 1 x 10-4 and 2 x 10-3, respectively. These are at, or slightly above, USEPA's recommended cancer threshold of 1 x 10-4.
6. Ecological Risk Assessment
In the risk characterization, the results of the toxicity assessment and the exposure assessment were integrated into a statement about the risk to the assessment endpoints. The risk characterization focused on the aquatic communities of the recharge basins of OU III, and the terrestrial organisms exposed to those recharge basins. The soil contamination to which terrestrial organisms could be exposed was limited to two areas: one area at the TCE Spill Area (AOC 19) is in a courtyard and thus virtually inaccessible to wildlife, and the other area occupies a very limited area within the developed portions of OU III at the Building 830 UST Area (AOC 12). Therefore, exposure of terrestrial wildlife to soil contaminants is insignificant.
Based on a comparison of surface water concentrations to New York State standards, the screening level risk assessment indicated that the most significant risks to the aquatic communities are due to copper in all three recharge basins investigated: Recharge Basin HT, Recharge Basin HN01, and Recharge Basin HN02. In addition, cadmium concentrations in Recharge Basin HN01 were elevated. As expected with a screening level assessment, the estimated risk is very conservative; it was estimated by comparing dissolved metal criteria to a measured total metal concentration, which will necessarily overestimate the risk. Dissolved concentrations are likely to be below the standard concentrations. 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, intermittent water, high temperature, and low dissolved oxygen. Recharge basins are not expected to be able to function as Class D waterbodies; therefore, risk to potential aquatic biota is not significant.
The potential risk to the benthic community was most prevalent in Recharge Basin HT, located at the North End of the LINAC, AOC 20 based on the screening level assessment. 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, only a limited benthic community is expected to be able to inhabit the recharge basins. Because a screening level assessment is intended to be conservative, applying the sediment criteria to recharge basins is expected to overestimate the risk to the actual community which could occur there. The sediment screening levels are aimed at protecting the majority of benthic species, including the sensitive ones. The benthic community expected to live in the recharge basins usually is the tolerant facultative species; therefore, risk is minimal.
Though a potential discharge of groundwater containing VOCs was predicted to occur after 30 years into a reach of the Carmans River, no risk was predicted. The conservatively estimated maximum concentration is orders of magnitude below the benchmark values for VOCs.
Consumption of surface water by terrestrial animals from the Recharge Basins of OU III was determined to represent no risk. Surface water concentrations of the constituents of ecological concern (COECs) were orders of magnitude less than the target species' (i.e., cottontail rabbit) drinking water no-observed-effect concentration.