New Brighton / Arden Hills

In the early 1980s, VOC contamination was discovered in the regional groundwater north of the City of St. Paul. Contamination was ultimately traceable to historical disposal practices at the Twin Cities Army Ammunition Plant (TCAAP) and led to the listing of the New Brighton/Arden Hills Site on the NPL in 1983.

The NB/AH Site includes the 4 square miles of TCAAP and the approximately 20 square miles of contaminated groundwater which has migrated past the TCAAP boundary. The Site also includes 14 on-site disposal or source areas where surface and subsurface soils have been contaminated by VOCs and other organic and inorganic contaminants.

Since the listing of the NB/AH Site, numerous interim removal actions, and actions selected through interim action RODs, have taken place to protect the surrounding communities from exposure to contaminated groundwater and to address on-site sources of contamination and contaminated media. The most significant groundwater remedies to date involve a) the extraction and treatment of contaminated groundwater and the subsequent use of that water in the municipal water supplies of the Cities of New Brighton and Fridley; b) the creation of a boundary groundwater recovery system (BGRS) to prevent any further migration of contaminated groundwater past the TCAAP boundary. This system was later expanded, with the installation of source control wells, into the TCAAP Groundwater Recovery System (TGRS).

Remedies to address other media on TCAAP have included: soil washing/soil leaching of inorganic contaminants from soils at a former burn and burial area (Site F); incineration of 1400 cubic yards of PCB-contaminated soil (Site D); soil vapor extraction (SVE) systems installed at former solvent disposal areas (Sites D and G); cleaning of the TCAAP sewer system (Site J); containment of surficial aquifer contamination (Site A); and containment of contamination underneath operating buildings (Sites I and K).

Currently a comprehensive Feasibility Study to address on-base soils and groundwater contamination is under review by U.S. EPA and MPCA. Both agencies provide oversight of cleanup activities at this U.S. Army-lead site through the provisions of the TCAAP Federal Facility Agreement, the first agreement of its kind, negotiated in 1987. Finally, investigations of additional potentially contaminated areas within TCAAP, as well as continuing ecological studies, are ongoing, with continued oversight by the regulators and an active Restoration Advisory Board (RAB).

(see the Army IOC pages , the DTIC site , the Federal Remediation Technologies Roundtable pages.

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