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Record of Decision System (RODS)



City & State:  IDAHO FALLS  ID  83401
EPA ID:  ID4890008952
EPA Region:  10
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R10-92/036
ROD Date:  12/05/1991
Operable Unit(s):  05
Media:  Sediment
Contaminant:  Metals, Inorganics, Radioactive Materials
Abstract:  SITE HISTORY/DESCRIPTION: The Idaho National Engineering Laboratory (INEL), located 32 miles west of Idaho Falls, Idaho, occupies 890 square miles of the Eastern Snake River Plain. Land use at the INEL is industrial and mixed use, with a surrounding 500 square mile buffer zone used for cattle and sheep grazing. The 7,700 INEL employees use the Snake River Plain Aquifer that underlies the site, as a drinking water source. The aquifer has been proposed as a sole-source aquifer pursuant to the SWDA. The TRA contains high neutron flux nuclear test reactors. The Warm Waste Pond is located 200 feet east of the test reactor area. The Warm Waste Pond is composed of three wastewater infiltration/evaporation ponds. Over the past 40 years, the Warm Waste Pond received discharges of reactor cooling water, radioactive wastewater, and regenerative solutions from ion exchange columns. As a result of an investigation conducted in 1988, it was revealed that a release of radioactive and/or hazardous contaminants to the Warm Waste Pond had resulted in contamination of the pond sediment and subsurface water. The INEL is divided into 10 Waste Area Groups (WAGs), which are further subdivided into operable units to facilitate characterization and remedy selection for similar or unique contamination issues. This ROD addresses the interim remedy for the Warm Waste Pond sediment that are part of the WAG 2 group that includes the TRA. Other OUs are associated with this interim action and will address perched water below TRA. Contamination of the Snake River Plain Aquifer and complete evaluation of risks associated with the Warm Waste Pond will be addressed in separate investigations and remedial actions, as necessary. The contaminants in the perched water, currently being evaluated in an ongoing RI/FS, will be addressed in future remedial actions. The primary contaminants of concern affecting the sediment are metals, including hexavalent chromium; other inorganics; and radioactive materials. PERFORMANCE STANDARDS OR GOALS: Federal and state clean-up standards for cesium-37, cobalt-60, and chromium have not been established at this time. Clean-up objectives for cesium37 are based on a 10[-4] to 10[-6] range for cancer risk to human health. Because this action does not constitute a final remedy for this operable unit, subsequent actions will fully address risks posed by the Warm Waste Pond sediment and associated contamination. INSTITUTIONAL CONTROLS: Deed restrictions will be implemented to prevent human exposure to site contaminants and provide site security.
Remedy:  SELECTED REMEDIAL ACTION: The selected remedial action for this site includes onsite physical separation of large and fine-grained materials, followed by treatment of 20,700 cubic yards of very-fine grained contaminated sediment onsite by chemical extraction with an acidic solution to remove cesium-137, cobalt-60, and chromium, followed by recovering contaminants from the acidic solution using ion exchange, precipitation or distillation; testing residuals, and treating tomeet applicable storage and/or disposal criteria, then storing the waste onsite temporarily until final disposition can be determined; returning larger grained materials to the pond and along with the treatment process residuals, and backfilling and revegetating the area; conducting pilot studies to optimize the extraction process; and implementing institutional controls including deed restrictions. The estimated capital costs for this remedial action are $7,195,000, with an estimated O&M cost of $300,000 over 18 months.
Text:  View full-text ROD [ 65K ]
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