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Record of Decision System (RODS)



Address:  JCT HWY 10 & MN HWY 96S 
City & State:  NEW BRIGHTON  MN  55112
County:  RAMSEY
EPA ID:  MN7213820908
EPA Region:  05
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R05-92/210
ROD Date:  09/30/1992
Operable Unit(s):  09
Media:  Ground Water
Contaminant:  VOCs, Other Organics, Metals
Abstract:  SITE HISTORY/DESCRIPTION: The 25-square-mile New Brighton/Arden Hills site includes the 4square-mile Twin Cities Army Ammunition Plant (TCAAP) in Ramsey County, Minnesota. Land use in the area is predominantly residential with commercial and industrial sectors. The estimated 100,000 residences, located within 2 miles of the site, along with adjacent townships use various glacial and bedrock aquifers as their drinking water supply. The TCAAP facility, a small arms manufacturing facility, is currently operated by the Federal Cartridge Company (FCC) and used by two manufacturing lessees, Alliant Techsystems and 3M Corporation. Since 1941, the plant has manufactured, stored, and tested small arms ammunition and related materials. From 1941 to 1981, waste materials, which included VOCs, heavy metals, corrosive materials, and explosives, were disposed of at 14 source areas located within TCAAP. In addition, breaks and leaks in sewerlines, where other disposal occurred, may have contributed to onsite and offsite ground water and soil contamination. In 1981, state investigations of municipal and private drinking water wells in and around TCAAP identified contamination of ground water, onsite soil, sediment, and surface water by VOCs, other organics, and metals. Past removal actions and seven previous RODs, signed from 1983 to 1989, addressed interim remedial actions conducted by the Army and Alliant Techsystems and provided for the establishment of alternate drinking water supplies for surrounding communities, onsite in-situ soil vapor extraction; installing ground water pump and treat systems to remediate ground water onsite; boundary ground water recovery systems to prevent further migration of VOCs; thermal treatment of PCB-contaminated soil, and the cleaning, repairing, and testing of contaminated sewer lines. This ROD addresses remediation of the south plume of offsite contaminated ground water, as OU3. Future RODs will address the offsite north plume of contaminated ground water, as OU1, and the onsite soil, sediment, surface water, and ground water, as OU2. The primary contaminants of concern affecting the ground water are VOCs, including benzene, TCE, and xylenes; other organics including phenols; andmetals, including chromium, lead. PERFORMANCE STANDARDS OR GOALS: Chemical- specific ground water clean-up standards, which are based on state standardsand SDWA MCLs and MCLGs, include 1,1-dichloroethane 70 ug/l; (state); 1,1-dichloroethene 6 ug/l (state); cis-1,2-dichloroethene 70 ug/l (MCL); 1,1,1- trichloroethane 200 ug/l (MCL); 1,1,2-trichloroethane 3 ug/l (proposed MCLG); and TCE 5 ug/l (MCL). INSTITUTIONAL CONTROLS: Institutional controls to restrict the drilling of private wells will prevent consumption of contaminated water until clean-up standards are achieved.
Remedy:  SELECTED REMEDIAL ACTION: The selected remedial action for this site includes pumping and offsite treatment of contaminated ground water at the leading edge of thesouth plume using precipitation and filtration to remove inorganic solids and a pressurized granular activated carbon system to remove VOCs; discharging the treated ground water offsite to the potable water supply of the City of New Brighton; disposing of filtration residuals and spent carbon offsite; implementing institutional controls including ground water use restrictions; and monitoring ground water. The estimated present worth cost for this remedial action is $4,851,000, which includes an annual O&M cost of $276,000 for 30 years.
Text:  View full-text ROD [ 53K ]
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