Over the next several months, the U.S. Department of Energy (DOE) and Brookhaven National Laboratory (BNL) will be seeking public input on alternatives for remediating contamination found near the Lab's Sewage Treatment Plant.
The plant, used to process sanitary and industrial sewage from the Lab's facilities, is located in the eastern-central portion of the site. Approximately 800,000 gallons per day of treated water are discharged from the plant into the headwaters of the Peconic River, on BNL property north of the plant. The complex includes several processing buildings, a settling tank, six active sand filter beds and two storage ponds.
Investigation results
An investigation of the area found elevated levels of heavy metals (e.g. silver and mercury), and low levels of radionuclides (including cesium-137), in surface and subsurface soils at the sewage treatment plant. Downstream of the plant's discharge, on the BNL site, sediment samples indicated the presence of heavy metals and low levels of radionuclides.
The sewage treatment plant area was first used by the Army camp that formerly occupied the BNL site during world wars I and II. BNL began using the sewage plant area in 1947, and this contamination can be attributed to past disposal practices at the site.
Because the Laboratory's disposal practices have changed, current effluent from the plant is not expected to cause such contamination. Since 1970, the effluent from the facility has been regulated by the New York State Department of Environmental Conservation (NYSDEC). Today's Laboratory discharges are monitored daily, and meet the stringent requirements of a NYSDEC permit.
The investigation also determined that low levels of tritium and volatile organic compounds, including trichloroethene (TCE), are present in area groundwater. TCE was commonly used in industry and at the Lab as a degreasing agent to remove oil and other petroleum products from metal parts and machinery.
Low levels of tritium are routinely discharged from the plant, and may enter groundwater through the river's bed. In 1995 and 1996, 17 groundwater monitoring wells between Wading River Road and the plant were sampled and tested for tritium. The highest levels detected were approximately one-tenth of the drinking water standard. Eight of the wells sampled showed no detectable tritium.
Actions taken
In 1996, 64,000 gallons of sludge containing some low-levels of radioactivity were removed from two World War II-era settling tanks (Imhoff tanks) at the plant and shipped to an off-site, permitted waste disposal site. The tanks were dismantled and the area was covered with clean fill in a project completed earlier this year.
The Sewage Treatment Plant is currently being upgraded, with construction expected to be completed by the end of 1997. The new design will employ ultraviolet disinfection and two aeration tanks to significantly reduce the amounts of nitrogen and organic matter being discharged from the plant.
The Lab is now focusing on possible sediment remediation alternatives, and a public meeting will be held early next year to discuss remediation alternatives.
Risks assessed
Food chain models determined that potential risks to fish and other aquatic species exist, particularly from exposure to silver and mercury, and an additional study was conducted to measure the levels of these contaminants in Peconic River fish.
Fish and sediment samples were collected from 12 stations in the river located between the Sewage Treatment Plant and Forge Pond in Riverhead (12 miles downstream from the plant) and analyzed for metals, pesticides, polychlorinated biphenyls (PCBs) and radionuclides.
Bioaccumulation studied
Preliminary data, now being validated, indicate measurable levels of mercury and PCBs in fish collected on the Laboratory site, downstream of the Sewage Treatment Plant. No off site fish were collected with detectable levels of PCBs.
Once validated, the results will be forwarded to the EPA and N.Y. State Department of Environmental Conservation for review, then included in the remedial investigation/risk assessment report.
Additional studies
An additional study was conducted to explain why the levels of metals in fish are lower than expected relative to the sediment concentrations. These data indicate that sulfides naturally present in the sediment are combining with the metals, preventing them from being ingested by fish.
A toxicity study to analyze ecological impacts was also undertaken to set cleanup goals for the sediments. Results from this study will be part of the remedial investigation/risk assessment report.
Remedial alternatives identified
The remediation alternatives being considered for Peconic River sediments include:
Both the "no action" and "source removal" alternatives have positive and negative aspects to consider before a final remedy is chosen. Under the "no action" alternative, the source would remain and the ecosystem would remain undisturbed. This alternative would rely on natural sedimentation to minimize exposure of aquatic life to contaminated sediments.
Source removal would include the excavation of contaminated sediments, but could spread contamination further downstream. It would also require the construction of a road through a heavily forested area, as well as the wetland area surrounding the river. This, along with the use of backhoes or bulldozers to remove the sediment, would result in considerable wetland disturbance or destruction.
The "no action" alternative might actually be more protective to wildlife than the source removal alternative because the ecosystem would not be negatively affected by the excavation process.
Phytoremediation is not expected to be an effective strategy for treating the contamination in place, but is being considered for treating the excavated sediments if the source removal alternative is chosen.
Comments sought
Remediation alternatives will be compared in the "Operable Unit V Feasibility Study" and the "Operable Unit V Proposed Plan," which are expected to be released in early 1998. These two reports will explain remediation alternatives and document the comparison of those alternatives to seven U.S. Environmental Protection Agency (EPA) criteria, which help determine the best option. The proposed plan will document the alternative that BNL, DOE, EPA and NYSDEC believe is most protective of human health and the environment.
The EPA criteria include "public acceptance" of the alternative. DOE and BNL are actively seeking comment on the various remediation alternatives, and scheduled opportunities for public input will include official comment periods this fall on the remedial investigation/risk assessment report, and this winter on the feasibility study and proposed plan. Poster sessions and a public meeting early in 1998 will provide additional feedback to DOE and BNL.
The "Operable Unit V Remedial Investigation and Risk Assessment
Report" will be available for review and comment this fall at the Lab's
information repositories (for locations, see above).