The U.S. Department of Energy (DOE) and Brookhaven National Laboratory (BNL) are currently evaluating remediation options for portions of a groundwater contaminant plume extending beyond the Lab's southern boundary.
To date, the Environmental Restoration Division (ERD) has detected six distinct chemical groundwater plumes emanating from known and unknown sources within the Lab site (see story, page 4). One of these plumes, originating from the center of the site, extends into an area of North Shirley/East Yaphank just south of the Lab's southern boundary.
The off-site part of the plume is comprised primarily of carbon tetrachloride, a solvent once widely used at the Lab and in industry for degreasing equipment. The solvent has been detected in on- and off-site monitoring wells at depths of 180-300 feet, at concentrations as high as 5,100 parts per billion (ppb). This is approximately 1,000 times the U.S. Environmental Protection Agency (EPA) and New York State drinking water standard of 5 ppb.
Sampling, hookup complete
In 1995, when the plume was detected, DOE and BNL, in cooperation with Suffolk County, began a residential well sampling program in the area to ensure no contamination from BNL was affecting private wells. Although the results showed no contamination from BNL above drinking water standards, DOE offered homes in the area free connections to public water as a precautionary measure.
Construction of a pump-and-treat system to address the on-site portion of the plume was completed in June, preventing any further off-site migration of high levels of solvents. BNL is investigating alternatives for treating the portion of the plume that has already moved off site.
Although there is no "pathway" of exposure for area residents, the contamination is at a high enough concentration that DOE and BNL are planning to actively remediate the plume. A groundwater treatment system will be constructed where contaminant levels are highest. The two treatment systems being considered for this action are:
Currently, three pump-and-treat systems are operating at BNL, and they have proven effective in removing VOCs from groundwater. In-well air sparging, meanwhile, has also been effective in removing contamination at other sites and in a pilot study performed last year at BNL. An evaluation of these two technologies will be documented in a "pre-design report," scheduled for completion by the end of 1997.
The Operable Unit III Remedial Investigation/Risk Assessment report is expected to be available for review in early 1998 at the Lab's four information repositories (for locations click here).