PECONIC RIVER INVESTIGATION AT
BROOKHAVEN NATIONAL LABORATORY
William H. Medeiros
Brookhaven National Laboratory
Office of Environmental Restoration
Dan Duh
IT Corporation
Mohammad Ali
U.S. DOE - Brookhaven Group
Gail Penny
U.S. DOE - Brookhaven Group
ABSTRACT
The Brookhaven National Laboratory (BNL) environmental restoration program is conducted under an Interagency Agreement (IAG) among the U.S. Department of Energy, the U.S. Environmental Protection Agency and the New York State Department of Environmental Conservation. The IAG integrates the requirements of the Comprehensive, Environmental Response Compensation and Liability Act, the Resource Conservation and Recovery Act and State regulations. The Operable Unit V Remedial Investigation and Feasibility Study addresses contaminated sediments in the Peconic River from historical discharges from the BNL Sewage Treatment Plant. DOE, BNL and the regulatory agencies are currently evaluating the need for remediation.
This paper will provide an overview of Operable Unit V and a status of progress to date. Characterization activities; bioaccumulation studies, interim actions, and remediation goals will be discussed.
INTRODUCTION
The Brookhaven National Laboratory (BNL) environmental restoration program is conducted under an Interagency Agreement (IAG) among the U.S. Department of Energy, the U.S. Environmental Protection Agency and the New York State Department of Environmental Conservation. The IAG integrates the requirements of the Comprehensive, Environmental Response Compensation and Liability Act, the Resource Conservation and Recovery Act and State regulations. The Operable Unit V Remedial Investigation and Feasibility Study addresses contaminated sediments in the Peconic River from historical discharges from the BNL Sewage Treatment Plant. DOE, BNL and the regulatory agencies are currently evaluating the need for remediation.
This paper summarizes information from two draft documents: 1.) The Operable Unit V Remedial Investigation Report; and 2.) the Operable Unit V Feasibility Study. The Remedial Investigation Report describes the nature and extent of contamination at the site. The Baseline Risk Assessment portion of this document reports on the risk to both human health and the environment in the absence of cleanup. The Operable Unit V Feasibility Study describes how the cleanup options were developed and evaluated.
SITE BACKGROUND
BNL is a U.S. Department of Energy (DOE) owned laboratory conducting research in physical, biomedical, and environmental sciences, as well as in some energy technologies. . The laboratory is situated on property owned between 1917 and 1947 by the U.S. Army and operated as Camp Upton during World Wars I and II. In 1947, the property was transferred to the Atomic Energy Commission for the purpose of establishing a national laboratory. BNL was operated by Associated Universities, Inc., a not-for-profit research management organization, under contract with the Atomic Energy Commission, the Energy and Research Development Administration and finally DOE until March 1, 1998 when Brookhaven Science Associates (BSA) assumes operations as the new contractor.
BNL is located 60 miles east of New York City, close to the geographic center of Suffolk County on Long Island, New York (Figure 1). It is bordered on the west by the William Floyd Parkway, on the east by residential areas and park land, on the north by residential areas, and on the south by the Long Island Expressway.
Fig. 1. Regional site location map.
In 1980, the BNL site was placed on the New York State Department of Environmental Conservation's (NYSDEC) list of Inactive Hazardous Waste Disposal Sites. In 1989, it was included on the federal National Priorities List of Superfund sites. BNL's inclusion on the Superfund and NYSDEC lists was primarily due to the effects of past operations, which pose a potential threat to Long Island's sole source aquifer. BNL has a total of 29 Areas of Concern (AOCs). To ensure more effective management of them, these areas were grouped into six distinct Operable Units. Operable Unit V is the third of these to be addressed. Operable Unit V consists of three areas of concern: Sewage Treatment Plant (AOC 4); Leaking Sewer Pipes (AOC 21); and, the Eastern Tritium Plume (AOC 23).
The Remedial Investigation sought to identify the nature and extent of soil and groundwater contamination in the area associated with the Sewage Treatment Plant and Peconic River and was conducted in several phases from 1995 through 1997. The investigation included the following: geophysical and biological surveys, sampling of soil, groundwater, surface water, and sediment; chemical and radiological analyses; benthic invertebrate toxicity testing; fish bioaccumulation studies; data validation; and preparation of the Remedial Investigation and Risk Assessment Report.
Sewage Treatment Plant
The BNL Sewage Treatment Plant (STP) has been located in the same area adjacent to the Peconic River in the northeast quadrant of BNL since its original construction by the Army in 1917. The current STP was built in stages from 1940 through 1944, and received major upgrades in 1967 and 1997. The STP provides tertiary treatment to about 0.8 million gallons per day of sanitary sewage for BNL facilities and consists of a clarifier, a modular aeration system with a secondary clarifier, and a sand filtration system (i.e., filter beds) for effluent polishing and an ultra-violet disinfection system. Treated effluent is discharged into the headwaters of the Peconic River to the north of the treatment facility.
Peconic River
The Peconic River headwaters at BNL begin off site approximately 1.2 kilometers upstream from BNL; the stream channel enters the lab at its north west perimeter, and exits the lab at its south east perimeter where it eventually joins with other headwater streams and becomes the Peconic River (Figure 2). The Peconic River and its drainage is considered a significant habitat, and portions of it are designated as a Wild, Scenic and Recreational River by the New York State.
Fig. 2. Peconic River.
Upstream of the STP water level in the stream channel and wetlands is determined by the water table elevation and usually only provides flow during periods of high precipitation during late winter and spring. On-site, virtually all of the flow is often supplied by the STP, especially during summer and fall. Except during periods when high precipitation elevates the water the river usually completely recharges to ground water before the stream channel leaves the site. Standing water is often absent from the stream channel until the confluence of the stream channel with the northern branch of the headwaters about two kilometers downstream from the site perimeter.
The habitat potential of the on-site headwaters to the Peconic River are limited due to low water levels, lack of cover, low nutrient levels, and elevated (or fluctuating) temperature levels related to the low water levels and lack of cover. Although the STP alters the natural flow of the on-site headwaters from intermittent to perennial, available aquatic habitat would be greatly reduced without its discharge. Wetlands downstream of the STP often contain water because of the STP discharge, though the water levels fluctuate seasonally. These wetlands serve as habitat for fish and wildlife and function in ecosystem filtering.
Peconic River Characterization
Sediment and surface water samples were collected from stretches of the stream channel from upstream of the STP effluent discharge point to approximately 20 km downstream of the discharge point. The location of sampling points was biased to include areas with the highest potential for accumulating contaminants. These areas were located in regions of the river where the stream widened and velocity decreased resulting in enhanced deposition. Surface water and sediment samples were collected from the same locations.
The surface water samples were collected prior to sediment samples as grab samples at the mid-channel locations, as appropriate. Surface sediment samples (top 6 inches) were collected with an Ekman dredge; one to three foot composite samples were collected with a hand corer. Water samples were collected at the surface
Peconic River sediments on-site were found to contain metals (notably mercury and silver), Polychlorinated Biphenyls (PCBs), and cesium-137 above screening levels established by NYSDEC. These screening levels are used to determine the potential for environmental risk and, if exceeded, trigger the need for more extensive studies and ecological risk assessment work. NYSDEC has developed surface water standards and sediment screening levels for most of the constituents examined in this study which are presented in Table 1. All detected concentrations exceeding these standards and screening levels are listed. In addition, the State Pollution Discharge Elimination System (SPDES) permit under which the STP operates sets limits for the discharge of certain contaminants. The permit limits for those contaminants which were detected in surface water during this study are also presented in Table 1.
Table I. Summary of Surface Water and Sediment Concentrations above Screening
Levels Additional Fish Tissue Bioaccumulation Study
Brookhaven National Laboratory
Only copper, mercury, and silver were detected at levels above the surface water standards, and all exceedances were located on-site. None of these exceeded the SPDES permit limits.
All six metals were found above the NYSDEC lowest effect screening levels for sediment. The lowest effect level is the most stringent of the NYSDEC screening criteria. No screening levels are available for radionuclides in sediment. Screening levels for soil were developed for the protection of human health in the Remedial Investigation. These are used for comparison in Table 1. Only cesium-137 exceeds its screening level. Contamination was highest in an on-site depositional area approximately 1 mile downstream of the STP.
According to NYSDEC guidance (NYSDEC, 1994), if sediment criteria are exceeded more information is needed to determine if remediation is necessary and what actual risks, if any, may be present. Because several of the contaminants in the sediment exceeded the sediment criteria and have the potential to bioaccumulate in biota there are potential human and wildlife risks. These risks were further evaluated with characterization studies including toxicity tests using benthic invertebrate species, fish bioaccumulation studies and acid volatile sulfide studies as well as human health and ecological risk assessments. The results of these studies are discussed below.
Benthic Invertebrate Studies
The assessment indicated that, in the areas with the highest levels of mercury or silver, the benthic invertebrate community is impacted; however, in general, the sediment contaminants are limited in their bioavailability. The areas of impact are located on-site and downstream of the STP in three depositional areas. The general lack of flow off-site reduces the opportunity for significant transport of contaminants downstream of the site.
Fish Bioaccumulation
During the Spring of 1997, additional fish bioaccumulation studies were conducted to supplement limited sampling conducted earlier in the Remedial Investigation. NYSDEC personnel selected the sampling stations and collected, measured, weighed, tagged, froze, and shipped the fish to a New York State Department of Health certified analytical laboratory. Sampling locations were selected to include two background locations which were within the Peconic River watershed but not hydraulically connected with the Peconic River, three on-site Peconic River locations and four off-site Peconic River locations extending to the town of Riverhead approximately 20 kilometers downstream from the discharge point. With the exception of the most upstream station at the STP discharge, all Peconic River samples were collected in depositional areas to maximize the potential to sample the areas with the highest contamination levels. At each location sediment and surface water samples were also collected and analyzed.
The availability of contaminants in sediment to aquatic organisms is somewhat restricted by the presence of sulfides and organic matter in the sediment. The concentration levels found in fish are shown in Tables II (inorganics, pesticides, PCBs) and 3 (radionuclides). Fish collected from the on-site Peconic River headwaters indicated biological accumulation (bioaccumulation) of principally PCBs and mercury. Off site fish had much lower levels.
Table II. Comparison of Fish Tissue Concentrations with FDA Action Levels and
Risk-Based Screening Levels Additional Fish Tissue Bioaccumulation
Study Brookhaven National Laboratory
HUMAN HEALTH AND ECOLOGICAL RISK SUMMARY
The presence of contaminants in the sediments of the Peconic River are of concern due to their ability to bioaccumulate and pose a potential risk to wildlife and humans who consume potentially contaminated fish. This study attempted to address this through the collection of fish from both on the BNL site and off-site. These fish were analyzed for those constituents determined to be of concern. This included some metals, pesticides, PCBs, and radionuclides.
Human Health Risks
The Food and Drug Administration (FDA) has published action levels for several contaminants which have been recognized as potential fish bioaccumulation human heath risks. Several of these were analyzed during this study. The FDA action levels are presented in Table II. The FDA action levels represent average concentrations of contaminants in the edible portion of fish. This study only conducted whole body analysis, which included scales, skin, bone, heads, gut contents, and fins in the samples. This tends to present higher concentrations than are present in the edible portions alone. The average whole-body fish concentrations for fish collected on-site, for fish collected off-site, and for all fish collected are also presented in Table II.
Most of the metals analyzed for do not have FDA action levels for fish consumption. Risk-based screening levels were derived based on EPA guidance (EPA, 1995) for these constituents to represent the concentration of the constituent in edible fish tissue which should not be exceeded to avoid public health concerns.
The reference doses and risk-based screening levels are also provided in Table II for those contaminants which do not have FDA action levels for fish. As shown, all average whole-body fish concentrations are below the FDA action levels and the risk-based screening levels. Whole-body concentrations are appropriate for evaluating potential ecological risk but are conservative for evaluating potential human health risk.
The acceptable exposure is the FDA Action Level or, in the absence of an FDA Action Level, the oral reference dose. The FDA Action Levels and the reference doses for those constituents without FDA Action Levels are also listed The risk to humans from consumption of contaminated fish can be calculated by comparing the estimated exposure level over a specified time period with the appropriate acceptable exposure. This ratio is called the Human Health Risk Hazard Quotient. A quotient greater than one represents a risk.
All hazard quotients for human consumers are less than one and represent no risk. The quotient is highest for PCBs and mercury from the consumption of only on-site fish. Furthermore, consumption of on-site fish is very unlikely because access to the site is restricted, on-site fish are low in number and quite small. Off-site migration of on-site fish is limited by a gauging station at the site perimeter and because the stream frequently recharges to ground before reaching the site perimeter. The hazard quotients based on consumption of only off-site fish also indicates no risk as it is much less than that for on-site fish. The hazard quotients risk based on consumption of only off-site fish, only on-site fish, and both on-site and off-site fish is presented in Table 2.
The NYSDEC has established a guidance value of 10 mrem/yr above background for radionuclide exposure to soils. Other guidance values have been established by other agencies such as the 15 mrem/yr by EPA. To be protective of human health for the purposes of risk screening, this assessment has used the most restrictive guidance value (NYSDEC, 10 mrem/yr). The effective dose equivalent (EDE) is a prediction of the amount of radiation above background which could be consumed by ingesting food, in this case fish, containing radionuclides. The EDE is calculated following guidance given in (USEPA, 1989).
The only radionuclides detected in fish (Table 3) were cesium-137 and strontium-90. The EDEs for these radionuclides were calculated for each sampling station and are also presented in Table III. All EDEs are below the NYSDEC Guidance Value of 10 mrem/yr and none exceed 12% of this guideline.
Table III. Radionuclide Effective Dose Equivalent Analysis Results
Additonal Fish Tissue Bioaccumulation Study
Brookhaven National Laboratory
Ecological Risk
No regulatory guidance values have been established for protection of wildlife from exposure to contaminated fish. However, the potential risk to wildlife consumers of fish can be calculated through the comparison of potential exposure to laboratory-derived acceptable exposures using a mathematical model of exposure. This results in an Ecological Risk Hazard Quotient. The average on-site fish concentrations presented in Table II are used as the input to this model.
The potential exposure of wildlife to contaminants of ecological concern was modeled based on conservative assumptions, primarily consumption of only contaminated fish from on-site. The Ecological Hazard Index predicted that ecological risk could occur for the target species (mink and belted kingfisher) from feeding exclusively on on-site fish with elevated concentrations of mercury, PCBs, and DDD.
BASIS FOR CLEANUP
Based on the results of the Remedial Investigation, it was determined that contamination in sediments located in the depositional areas of the on-site Peconic River headwaters posed an ecological but not a human health concern. These sediments are primarily contaminated with metals and PCBs.
Alternative Evaluation and Recommendations
The balance of this document outlines the remedial action alternatives retained for Operable Unit V after initial screening of other alternatives and summarizes the analysis of each alternative against nine evaluation criteria established by EPA. Five alternatives were retained for detailed analysis in the Feasibility Study Report. These alternatives are briefly discussed below.
Alternative 1 (No Action): The no action alternative includes no remedial activities. In accordance with the National Contingency Plan, the No Action Alternative is required to be assessed for comparison to the other alternatives. This alternative includes continued monitoring of surface water and sediment.
Alternative 2 (Excavation/Drying Beds/Off-site Disposal): This alternative consists of the dewatering of segments of the stream followed by sediment excavation using conventional earthmoving equipment. The sediment that is removed is then placed in a drying bed, where free liquids are drained by gravity until the solids content of the sediment is sufficient for off-site disposal. The free liquids are then filtered and discharged to the Peconic River. The dewatered sediment can then be shipped off-site to a non-hazardous waste disposal facility.
Alternative 3 (Limited Excavation/Drying Beds/Sediment Dispersion Control/Off-site Disposal): This alternative is similar to Alternative 2 except that excavation will be limited to two of the three impacted areas. The area which would not be excavated is a large continuously wet, open water wetland which provides the majority of the aquatic habitat in the on-site portion of the Peconic River tributary. This alternative limits the impacts of remedial activities to the two less ecologically sensitive areas by leaving this area unexcavated. A silt screen would be used near the off-site boundary to enhance the depositional properties of the most downstream area and to prevent off-site migration of contaminated sediments that may be resuspend from the unexcavated area and migrate downstream during storm events. The most downstream depositional area would be excavated and periodically monitored to determine whether re-excavated may be necessary, in the event that contaminated sediments from upstream redeposit in this area.
Alternative 4 (Excavation/ Phytoremediation/Off-site Disposal): This alternative uses plants to remove contaminants from the Peconic River sediment. This process is known as phytoremediation, and may potentially be conducted either in the river (in-situ) or within growing fields containing the contaminated sediment (ex-situ). The alternative examined in detail involves the ex-situ treatment of contaminated sediments through phytoremediation; in-situ treatment was not evaluated because, to date, it is an unproven technology. For ex-situ treatment, the top six inches of surface sediment from the Peconic River known to contain mercury, copper, and silver at concentrations that exceed site cleanup goals is removed using the stream dewatering and conventional excavation techniques outlined for Alternative 2. The phytoremediation is conducted by placing the excavated sediment in a large, shallow drying bed which must be constructed near the excavation. The material in the drying bed is conditioned through the addition of fertilizer and lime, as necessary. Once the soil conditions have been optimized, the bed is tilled and seeded followed by irrigation. The plants are harvested at intervals of 6 to 9 weeks. After harvesting, the biomass containing the metals is cut and transported to an off-site treatment, storage, and hazardous waste disposal facility. The remaining sediments may be used for on-site backfill or grading the stream.
CURRENT STATUS AND NEXT STEPS
The preferred remedy has been identified by evaluating all of the alternatives against nine evaluation criteria established by EPA. The comparison of alternatives, including advantages and disadvantages, is summarized in Table 4. Based on an evaluation of the alternatives, BNL and DOE believe that the Alternative 2 represents the best balance of EPA's remedy selection criteria. NYSDEC and EPA are presently reviewing the draft Feasibility Study and proposed plan and a decision on the preferred alternative is expected in the spring of 1998. DOE and BNL are planning to finalize the various Superfund documents upon resolution of regulatory comments and seek public input during the spring and summer 1998.
Table IV. Summary of Comparative Analysis of Sediment Alternatives
REFERENCES