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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/R05-93/246
ROD Date:  09/30/1993
Operable Unit(s):  07
Media:  GW
Contaminant:  VOCs, Metals
Abstract:  The 25-square-mile New Brighton/Arden Hills site consists of the 4 square-mile Twin Cities Army Ammunition Plant (TCAAP) and portions of seven nearby communities: New Brighton, Arden Hills, St. Anthony, Shoreview, Mounds View, Columbia Heights, and Minneapolis, located in Ramsey and Hennepin Counties, Minnesota. Land use in the area is mixed residential, commercial, and industrial, with onsite wetlands and woodlands surrounding the Rice Creek watershed. The site consists of gently rolling, postglacial terrain with several hills and surface water bodies, including lakes and streams, but no extreme relief. The people who reside in the vicinity of the site use the aquifers which fall within the North Plume: the Prarie du Chien/Jordan Sandstone aquifer, the Hillside and Arsenal Sandaquifers, and the Lacustrine Deposits, as their drinking water supply. These aquifers supply water to TCAAP and the municipalities of New Brighton, St. Anthony, Fridley, Mounds View, and Shoreview. The TCAAP facility is an inactive small arms ammunition manufacturing plant. From 1941 to 1981, the site was used for the manufacture, storage, and testing of small arms ammunition and related equipment. Waste materials such as VOCs, heavy metals, corrosive materials, and explosives were disposed of at 14 source areas at TCAAP. In 1981, the State began ground water sampling and analysis which indicated that municipal and private drinking water wells and wells at TCAAP were contaminated with VOCs. As a result, beginning in 1981, the City of New Brighton abandoned several municipal wells and either placed them on standby or deepened several others: the Village of St. Anthony decommissioned one well and connected a portion of the village with nearby Roseville water supplies for an indefinite, but temporary period; a number of New Brighton/Arden Hills residents previously drawing ground water from contaminated private wells were provided with municipal water through the construction of a water main extension; and residents of a nearby trailer park drawing contaminated water were provided with new wells to supply potable water. Furthermore, additional Interim Remedial Actions were implemented as part of the Department of Defense's Installation Restoration Program, which included the removal of contaminated sludge and soil from Building 502 between 1984 and 1986; the construction of in-situ soil vapor extraction (SVE) systems for remediation of contaminated soil at Sites D and G on TCAAP in 1986; the cleaning of all sewer lines at TCAAP in 1986; the installation of a ground water pump-and-treat system at Sites A, I, and K in 1988; and the construction of permanent granular activated carbon treatment systems for the City of New Brighton in 1990 and the Village of St. Anthony in 1991. In 1987, an interim action ROD was written to implementa boundary ground water recovery system consisting of 12 wells to prevent migration contaminated ground water past the southwest boundary of TCAAP. A 1992 ROD addressed the containment of the South Plume by extracting ground water from its leading edge as 0U3, and the thermal treatment of approximately 1,400 yd[3] of PCB-contaminated soil at Site D in 1989. This ROD addresses the North Plume of offsite contaminated ground water. Future RODs will address onsite soil, ground water, sediment, and surface water, as 0U2. The primary contaminants of concern affecting the ground water are VOCs, including TCE; and metals. SELECTED REMEDIAL ACTION: The selected remedial action for this site includes providing an alternative water supply to residents with private wells under State drinking water advisories within the impacted zone; implementing a ground water extraction scheme for plume containment; treating the extracted ground water onsite by oxidation and filtration to remove iron and manganese, followed by pumping the treated water to a permanent onsite GAC system; discharging all treated water offsite to the New Brighton municipal distribution system; monitoring ground water; and implementing institutional controls, including ground water use restrictions. The estimated present worth cost for this remedial action is $10,310,000, which includes an estimated annual O&M cost of $704,700 for 30 years. PERFORMANCE STANDARDS OR GOALS: Chemical-specific ground water cleanup goals are based on SDWA MCLs or health-based State levels, and include 1,1-DCA 70 ug/l; 1,1-DCE 6 ug/l; cis-1,2-DCE 70 ug/l; 1,1,1-TCA 200 ug/l; 1,1,2-TCA 3 ug/l; and TCE 5 ug/l. INSTITUTIONAL CONTROLS: Institutional controls, including ground water use restrictions, will be implemented to prevent the drilling of private wells, thereby regulating the new exposure points within the contaminated areas of the site.
Remedy:  The NB/AH site has been divided into three operable units. The first operable unit, OU-1, addressed by the remedy selected in this ROD, consists of the North Plume of off-TCAAP contaminated groundwater. The second operable unit, OU-2, consists of the on-TCAAP soils, groundwater, sediments,and surface waters. A remedy for OU-2 is expected to be proposed in mid-1994. The third operable unit, OU-3, consists of the South Plume of off- TCAAP contaminated groundwater. A ROD has already been issued for OU-3, for which the selected remedy is to contain the South Plume by extracting groundwater from its leading edge, thus preventing further contaminant migration into areas that have not been impacted.

For OU-1, the major components of the selected remedy include the following:
. Providing an alternative water supply to residents with private wells within the North Plume
. Implementing drilling advisories that would regulate the installation of new private wells within the North Plume as a Special Well Construction Area
. Extracting groundwater at the containment boundary in the North Plume near County Road E
. Pumping the extracted groundwater to the Permanent Granular Activated Carbon Water Treatment Facility (PGAC) in New Brighton for removal of volatile organic compounds (VOCs) by a pressurized GAC system
. Discharging all of the treated water to the New Brighton municipal distribution system
. Monitoring the groundwater to verify the effectiveness of the remedy
Text:  View full-text ROD [ 42K ]
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