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Record of Decision System (RODS)

IDAHO NATIONAL ENGINEERING LABORATORY (USDOE)

Abstract

Site Name:  IDAHO NATIONAL ENGINEERING LABORATORY (USDOE)
Address:  AEC TESTING RESERVATION
US HWY 20/26 40 MI W OF IDAHO FALLS 
City & State:  IDAHO FALLS  ID  83401
County:  BUTTE,CLARK,JEFFERSON,BIN
 
EPA ID:  ID4890008952
EPA Region:  10
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R10-95/086
ROD Date:  12/02/1994
Operable Unit(s):  15
 
Media:  soil, groundwater
 
Contaminant:  Carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene
 
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Idaho National Engineering Laboratory (INEL) is a government facility managed by the U.S. Department of Energy (DOE), located 32 miles west of Idaho Falls, Idaho, and occupies 890 square miles of the northeastern portion of the Eastern Snake River Plain. The Radioactive Waste Management Complex (RWMC) is located in the southwestern portion of the INEL. The majority of the organic contamination associated with the Organic Contamination in the Vadose Zone (OCVZ) operable unit is within the subsurface. The highest contaminant concentrations are found immediately beneath the Subsurface Disposal Area (SDA), an area with several disposal pits and trenches previously used for the disposal of organic wastes. The SDA is an 88-acre area located within the RWMC. The RWMC encompasses 144 acres and consists of both the SDA and the Transuranic (TRU) Storage Area.

The RWMC was established in the early 1950s as a disposal site for solid, low level waste generated by INEL operations.

Current land use at the INEL is primarily nuclear research and development, and waste management. Surrounding areas are managed by the Bureau of Land Management for multipurpose use. The developed area within the INEL is surrounded by a 500-square-mile buffer zone used for cattle and sheep grazing.

The OCVZ operable unit is defined as the part of the vadose zone beneath and within the immediate vicinity of the RWMC where there are organic contaminants in the vapor state. The presence of the contaminants is the result of the burial at the SDA disposal pits of organic wastes from the Rocky Flats Plant in Colorado. OCVZ does not include the wastes remaining in the disposal area (i.e., contaminated solids, drums, etc.). It only includes those organic compounds that have migrated from the wastes. The organic compounds are primarily carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene.

Sampling conducted for the remedial investigation (RI) has documented that volatile organic compounds (VOCs) have migrated from the disposal pits into the vadose zone. In the vadose zone, VOCs are migrating both vertically and laterally away from the disposal pits. Vertical migration of contaminants occurs both by vapor diffusion and infiltration of moisture through the vadose zone. Lateral migration occurs primarily by diffusion of VOC vapors. VOCs have been detected in soil vapor, surficial soils, perched water and in the Snake River Plain Aquifer (SRPA).
 
Remedy:  The major components of the selected remedy include: installation and operation of five vapor extraction wells at the RWMC; installation and operation of off-gas treatment systems to destroy the organic contaminants present in the vapor removed by the extraction wells with off-gas treatment in the form of catalytic oxidation or an equally effective organic contaminant destruction technology; addition of soil vapor monitoring wells to monitor performance of the vapor extraction wells and verify the attainment of remedial action objectives as well as provide information used to evaluate potential modifications to the selected remedy to continue it beyond a first phase; and maintenance of institutional controls, which includes: using signs to restrict access, maintaining fences/barriers, and monitoring the existing production well supplying water to workers at the RWMC.
 
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