OU III Explanation of Significant Differences

May 2005

Under the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) an Explanation of Significant Differences (ESD) is required when a substantial change is made to a Record of Decision (ROD).

The Operable Unit III ROD, signed in June 2000, established the cleanup decisions for several groundwater contamination plumes at BNL. However, as described in the ROD, there were two areas in which additional characterization and investigation were required in order to determine the remedial actions, and one area where a pilot study was required before the implementation of the remedy. The two areas needing further characterization were identified in the ROD as the Building 96 geophysical anomalies and the volatile organic compound (VOC) contamination in the Magothy Aquifer. The area requiring a pilot study was the strontium-90 plumes associated with the Chemical Pits, the BGRR, and the Waste Concentration Facility located in the middle of the BNL site.

The selected remedy for the strontium-90 plumes in the OU III ROD was a pump-and-treat system using ion exchange technology. The ROD further stated that before implementation of the remedy, a pilot treatability study would be performed to evaluate the effectiveness of extraction and treatment and that the final remedy may be modified based on the results of the study.

The Department of Energy (DOE) completed the additional characterization of the areas and the strontium-90 pilot study. Detailed reports reviewed by the EPA, NYS Department of Environmental Conservation, and the SC Department of Health Services were finalized. The OU III ESD was signed by the EPA on May 13, 2005.

Community Input

While a public comment period is not required when issuing an ESD, one was provided to allow input from the community. The public comment period was held from December 15, 2004 through January 21, 2005. Two information sessions were held on January 11, 2005 and a mailing was sent out to BNL's mailing list of 2,300 interested community members. BNL's Community Advisory Council and DOE's Brookhaven Executive Roundtable were given presentations on the ESD and provided input.

Documents / Links

OU III Explanation of Significant Differences