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Record of Decision System (RODS)



City & State:  GOLDEN  CO  80402
EPA ID:  CO7890010526
EPA Region:  08
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R08-92/064
ROD Date:  04/06/1992
Operable Unit(s):  04
Media:  Surface Water
Contaminant:  VOCs, Metals, Radioactive Materials
Abstract:  SITE HISTORY/DESCRIPTION: The Rocky Flats Plant (USDOE) (Operable Unit 4) site is part of the 6,500-acre nuclear weapons research, development, production, and plutonium processing complex in Jefferson County, Colorado. The plant is composed of the 450-acre Rocky Flats Plant (RFP) security area and the remaining buffer area. Land use in the area is predominantly rural, agricultural, commercial, and industrial, with several residential areas within 5 miles of the site. Since 1951, the Department of Energy (DOE) has used the site for manufacturing components of nuclear weapons; processing plutonium; and fabricating, machining, and assembling components from metals. The central portion of RFP contains the Solar Evaporation Pond (SEPs) Waste Management Unit, including Ponds 207-A, 207-B North, 207-B Center, 207-B South, 207-C, and the Interceptor Trench System (ITS). The SEPs were formerly used to store and treat liquidprocess waste having less than 100,000 picocuries per liter of total long-lived alpha activity. These process wastes also contained high concentrations of nitrates as well as treated acidic wastes containing aluminum hydroxide. The ponds are known to have received other wastes, including sanitary sewer sludge, lithium chloride, lithium metal, sodium nitrate, ferric chloride, sulfuric acid, ammonium persulfates, hydrochloric acid, nitric acid, hexavalent chromium, tritium, and cyanide solutions. Sludge from the SEPs was removed periodically to implement repair work on the pond liners and as part of routine waste management activities. Removed sludge was mixed with Portland cement and solidified as a mixture of sludge and concrete for shipment for offsite disposal. In 1986, placement of process waste material into these ponds ceased. From 1971 to 1974, construction of interceptor trenches was initiated to prevent natural seepage and pond leakage from entering North Walnut Creek. In 1981, the system was replaced by the current ITS, which collects an estimated 4 million gallons per year for discharge to the 207-B ponds. This interim ROD addresses management and treatment of liquids contained in ponds 207-A, 207-B North, 207-B Center, 207-B South, and the water collected by the ITS as the OU4 at the site. Future RODs will address removal and solidification of sludge, further investigation, characterization, and remedial activities. The primary contaminants of concern affecting the surface water are VOCs, including TCE; metals,including chromium; and radioactive materials, including Pu[-239] and Am[-241]. PERFORMANCE STANDARDS OR GOALS: Chemical-specific surface water clean- up goals are based on sitespecific radionuclide standards and MCLGs or MCLs and attainment of relevant CWA water quality criteria. INSTITUTIONAL CONTROLS: Not provided.
Remedy:  SELECTED REMEDIAL ACTION: The selected interim remedial action for this site includes constructing and utilizing three temporary surge tanks and associated piping to contain and transfer water collected by the ITS; evaporating approximately 3 million gallons of water from pond 207-A and 5 million gallons of water from the 207-B ponds using onsite flash evaporators and associated tanks; transferring the distillate to a holding tank for reinjection into the Raw Water System for plant cooling tower usage; and collecting the flash evaporator concentrate in holding tanks, and onsite solidification of the residual; conducting treatability studies using surrogate pond water to simulate the proposed treatment system. The estimated total cost for this interim remedial action is $8,017,000, which includes an annual O&M cost of $1,170,000 for 3 years.
Text:  View full-text ROD [ 78K ]
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