Description of Peconic River and Sewage Treatment Plant Projects

During initial environmental studies, the Brookhaven National Laboratory (BNL) site was subdivided geographically into seven Operable Units (OU).

Operable Unit V is an area in the eastern-central portion of BNL. This area includes the Lab's sewage treatment plant, an active facility used to process sewage from the Lab's facilities. OU V also includes areas of the Peconic River impacted by past Laboratory operations, as well as sewer pipes and groundwater beneath the eastern portion of the Lab.

Peconic River

The Peconic River receives discharges from the Lab's sewage treatment plant. During the remedial investigation, elevated levels of heavy metals (such as mercury, copper, and silver), organic chemicals (such as polychlorinated biphenyls, or PCBs), and low levels of pesticides (such as DDD, a product of DDT degradation) and radionuclides were detected in Peconic River sediment. Most of the contaminants were found in the top six inches. As expected, contaminants are more prevalent in areas where more sediment is deposited by the river and decrease with distance downriver.

In February 2000, the U.S. Department of Energy (DOE) proposed the excavation of all Peconic River sediment containing contaminant levels higher than cleanup goals. The excavated sediment would be dewatered in drying beds and disposed of off site. In response to public comments, a workshop was held in December 2000 to further examine remedial alternatives. A final cleanup plan has not been selected yet.

Sewage Treatment Plant

The Laboratory's sewage treatment plant (STP) processes up to 1.25 million gallons of wastewater per day. Treated effluent is discharged into the Peconic River, north of the treatment facility. Discharges from this plant are regulated by the New York State Department of Environmental Conservation, and are routinely monitored for compliance. Monitoring results are reported in annual Site Environmental Reports.

The main areas of concern within the STP are the sand filter beds and berms. There are eight sand filter beds, each covering about one acre and containing three feet of sand on top of gravel and tile collection pipes. Wastewater is sent through the sand beds for filtering prior to release.

In the past, the Lab removed some soils from the sand filter beds after accidental releases of contaminants into the beds occurred. The contaminated material from the sand filter beds was piled onto adjacent areas known as sand filter berms. Thus, the soils with higher levels of contamination are located within these bermed areas.

Soils within the sand filter beds and berms contain elevated levels of mercury, silver, chromium and lead. Elevated levels of cesium-137 are found in a few isolated areas, primarily in the sand filter berms. Soil contamination is concentrated in the top six inches.

DOE and BNL propose that soils at the Lab's sewage treatment plant containing levels of contaminants above cleanup goals be excavated and shipped to a licensed off-site disposal facility. Excavated areas would be backfilled with clean soil and regraded. A final cleanup plan has not been selected yet.

Sewer Pipes

Some sanitary sewer lines at the Lab were installed as early as 1917, when the property was in use by the U.S. Army for Camp Upton. These old lines were repaired and upgraded by the Army in 1942. The Army constructed them from various materials, including vitrified clay, cast iron and reinforced concrete.

In 1987, BNL investigated these lines and discovered that they were leaking. The Laboratory replaced the sewer pipes leading to the sewage treatment plant with a new line in January 1993. The old pipes were capped and left in place.

In 1995, the Laboratory sampled soils surrounding the areas where leaks were identified along the retired and capped sewer line during the OU V investigation. The results of the investigation identified only a few areas with low concentrations of inorganic constituents. This indicates that the sewer line leading to the STP is not a source of significant contamination to the surrounding soils. As part of a more recent investigation, sludge was collected from the bottom of 10 manholes along the retired and capped sewer line and analyzed for radionuclides. The results identified elevated activities of two radionuclides - americium-241 and cesium-137.

The OU V sewer line has been retired and capped at both ends; therefore, no exposure pathway presently exists. Brookhaven will remove contaminated sludge from the 10 manholes along the retired sewer line.

Groundwater

Low levels of volatile organic compounds (VOCs), primarily trichloroethene, were detected in the groundwater of OU V. These VOCs are found at the site boundary east of the Lab's sewage treatment plant and beyond the Lab's eastern boundary. The highest level found on site in 2000 was 17.9 parts per billion (ppb). The maximum off-site level was 10.7 ppb, which is above the drinking water standard of 5 ppb.

The elevated levels of VOCs originated from discontinued past disposal practices that resulted in releases of VOCs to the Lab's sewage treatment plant. Investigations of soil and groundwater at the sewage treatment plant indicate that there are no continuing sources of VOC contamination.

The elevated levels of VOCs in groundwater off Laboratory property are found at depths (200 feet) below the depths of most residential wells. Homes and businesses in the OU V area were offered public water hookups in 1997 to protect against possible exposure to groundwater contaminants.

No action is proposed for OU V groundwater.VOC concentrations in groundwater are decreasing. Outpost monitoring wells have been placed along the predicted path of the groundwater and additional groundwater monitoring data will be collected. If future monitoring data suggest a need for a groundwater remedy, the OU V remedy will be modified.