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Congressional District # 04


EPA ID# MN7213820908
Last Updated: May, 2015

Site Description

The New Brighton/Arden Hills Superfund site consists of the Twin Cities Army Ammunition Plant (TCAAP) and all other areas of the surrounding communities historically contaminated by the migration of hazardous substances or contaminants from TCAAP.  Between 1941 and 1981, wastes were disposed at 14 areas, or sites, within TCAAP. The total area of the Superfund site, including the offsite contaminated groundwater plumes, is approximately 25 square miles.


Site Responsibility

The U.S. Army is the responsible party for the New Brighton/Arden Hills Superfund Site.  This site is being addressed through federal and state actions in accordance with the 1987 TCAAP Federal Facility Agreement.

Threats and Contaminants

The wastes disposed at TCAAP included volatile organic compounds (VOCs), semi-VOCs, metals, polychlorinated biphenyls (PCBs), cyanide, pesticides, and explosives.  The primary impact to the surrounding communities has resulted from VOC contamination of the regional groundwater resource, which is used for municipal and private water supplies. 

Within the TCAAP boundaries, soils were contaminated with solvents, semivolatiles, metals and PCBs.  In addition, a number of areas (Sites D, G, H and 129-15) were used as dumps.  Additionally, a number of areas (Grenade Range, Outdoor Firing Range), were impacted by lead from the testing of ammunition and grenades.  Finally, the transmission of industrial wastes via the storm sewer system into Round Lake, a 120 acre lake adjacent to TCAAP, a unit of the Minnesota Valley National Wildlife Refuge, resulted in the contamination of lake sediments with heavy metals and PCBs.

Cleanup Progress

In 1987, the Army, U.S. Environmental Protection Agency (U.S. EPA), and Minnesota Pollution Control Agency (MPCA) entered into a federal facility agreement (FFA) for the investigation and remediation of the site. In accordance with the FFA, the Army initiated numerous cleanup activities under the Department of Defense (DoD) Installation Restoration Program, including:

Additional action was taken and included the construction of a granular activated carbon (GAC) treatment system for the village of St. Anthony by U.S. EPA and MPCA.  The system was completed in 1991, pursuant to a September 1986 ROD.

In recognition of the need to expedite the remediation of regional groundwater contamination, U.S. EPA, MPCA, and the Army agreed to address the final remedy for the site in three stages or operable units. Operable Unit 1 (OU1) addresses the North Plume of contaminated groundwater which has migrated off-TCAAP; Operable Unit 3 (OU-3) addresses the smaller, South Plume.

RODs, in which remedies for these operable units were selected, were signed in 1992 and 1993. The remedies selected include:

The OU1 and OU3 RODs provide for containment pump-and-treat systems comprised of wells which serve the dual purposes of containment and municipal water supply for the city of New Brighton.  Construction and full operation of the OU3 system began in 1994. Construction of the OU1 system was completed in the second quarter, FY1999.

For a number of years, VOC levels in monitoring wells for the South Plume were consistently non-detect. In 2001, U.S. EPA and MPCA approved the Army's request to temporarily cease pumping of the OU3 extraction well-and-treatment system for remediation purposes and maintain it in "standby mode" with continued groundwater monitoring.  After a minimum of five years of non-detect VOC concentrations, the Army requested that the OU3 ROD requirement for operating the South Plume extraction well be terminated.   After reviewing all relevant groundwater monitoring data, U.S. EPA and MPCA concurred with the Army's request and in June 2006 signed the OU3 ROD Amendment.  The OU3 ROD Amendment removes groundwater extraction and associated remedy components and retains the alternate water supply, groundwater monitoring and institutional control components of the original remedy.

The last component of the final remedy for the site, a ROD for Operable Unit 2 (OU2), was signed in December 1997. The remedies selected in this ROD address contaminated soil and groundwater within the TCAAP boundary. Major elements of these remedies include:

By summer 1999, major components of the soils remediation component of the OU2 remedy had been designed and implemented. These components included:

By summer 2002, the following on-TCAAP remedial and removal actions had been completed:

The remaining cleanup action required by the OU2 ROD, excavation and installation of soil covers at Site C, was completed in May 2009.   An extensive long-term monitoring program for groundwater, surface water, and sediments is currently in place and will continue well into the future.

Between 2006 and 2009 the following activities were completed:

(1) reconfiguration/optimization of the TGRS;

(2) Operable Unit 1 ROD Amendment - A ROD Amendment for OU1 was signed in June 2006.  The purpose of this amendment is to improve the method by which success in the cleanup of the North Plume of off-TCAAP contamination is measured;

(3) Operable Unit 2 ROD Amendments - The OU2 ROD was amended to address needed changes to the remedies for various portions of the OU2 remedy(e.g., at Sites I, K, 129-15, and conditions at Site C).  The amendment process included: OU2 ROD Amendment 1, addressing changes in the soils remedy at Site C-2, was signed in July 2007.  Amendments Nos. 2 (Site I Groundwater) and 3 (OU2 Soils and Dumps) were signed in spring 2009, as were Explanations of Significant Difference (ESDs) for Groundwater (ESD 1) and Soil (ESD 2): remedy changes which are not significant enough to warrant amending the ROD;

(4) Operable Unit 3 ROD Amendment - A ROD Amendment for OU3 was signed in August 2006.  The purpose of this amendment is to eliminate the requirement for the OU3 extraction well, also known as the Plume Groundwater Recovery System (PGRS), as part of the OU3 remedy because its purpose, to prevent the spread of the OU3 plume at its leading edge, has been served.  The PGRS has been extracting clean water (i.e., non-detect for volatile organic carbon (VOC) contaminants) for at least five years.  The OU3 plume has receded significantly toward TCAAP, and it is expected to continue to recede.

(5) Building 102 Groundwater Plume - During performance of an Environmental Site Assessment (ESA) by the developer of the property transfer parcel of TCAAP, the developer's contractor discovered VOC contamination around Building 102.  Subsequent investigation by the Army of the Building 102 area, documented in the Groundwater Investigation Report for Building 102 (January 2006) delineated a plume of shallow VOC-contaminated groundwater originating underneath the building.  An EE/CA for the site was completed in July 2008.  The EE/CA recommended monitored natural attenuation as a non-time-critical removal action for the contaminated groundwater.  The removal action was implemented and completed  in 2009.

(6) Long-Term Operation and Maintenance Activities - These activities will continue to be monitored through the Annual Performance Report, which the Army will continue to generate for regulatory review until the cleanup at the Site is complete.

Ongoing activities include:

(1) Operation and maintenance of on-TCAAP groundwater remediation systems (Site A and TGRS); annual performance monitoring of the groundwater remediation systems; and annual private well inventory.

(2) Aquatic Sites Feasibility Study (FS) - A FS to address the findings of the 2005 Tier II Ecological Risk Assessment has gone through several interations.  U.S. EPA, MPCA and  the U.S. Army completed the FS for Rice Creek, Marsden Lake, Sunfish Lake and Pond G (all located on TCAAP) at the end of 2010.  A ROD Amendment (OU2 ROD Amendment #5) was completed in April 2014 (see below).  The ROD amendment addressed Rice Creek, Marsden Lake, Sunfish Lake and Pond G.  For Round Lake, ongoing activities are discussed below.

Amendment #4 to the OU2 ROD was completed in January 2012.  The amendment documents the selection of remedies for the aquatic sites that remain on the TCAAP property.  It also documents final remedies for sites where previous removal actions addressed the outstanding contamination issues with a No Further Action (NFA) decision.  These include Site K and Building 102.

Amendment #5 to the OU2 ROD was completed in April 2014.  The amendment documents the selection of a remedy for areas of TCAAP which were not included in the original ROD because they were either still considered operational or were discovered subsequent to the ROD.  The selected remedy for the areas in question (Site A, 135 Primer/Tracer Area, Environmental Baseline Study Areas) is land use controls (LUCs).  the LUCs involve restricting the property use in the subject areas to uses that are compatible with industrial use.  Residential development will not be allowed.  Technically, this LUC is already in place given the "blanket" LUC described in the OU2 Land Use Control Remedial Design document.

In 2010 U.S. EPA and MPCA approved the Army's Land Use Control Remedial Design (LUCRD) document.  The LUCRD defines the LUCs required on the TCAAP property and the roles and responsibilities, primarily of the Army, in implementing, maintaining, monitoring and enforcing the LUCs.

Operable Unit 10 (Round Lake) - The Army collected a substantial amount of additional sediment data in Round Lake during the summer of 2011. Subsequent to the collection of the sediment data, Army submitted a partial feasibility study for Round Lake. Disagreement over the significance of the sediment contamination between the Army and the USEPA and MPCA has delayed the selection of a remedy to address the ecological risk posed by contaminated sediments in Round Lake. In November 2013, the Army submitted a Supplemental Risk Assessment/Feasibility Study for Round Lake to USEPA and MPCA. EPA and MPCA commented upon the SRI/FS in early 2014, and did not concur with the Army's risk conclusions or the proposal for no action at Round Lake.  Since June 2014, the regulators and the Army have been engaged in informal dispute resolution over the Round Lake FS.  Consultation continues, with the expectation that it will be completed in the summer of 2015 and that the Army will produce a FS acceptable to the regulators by the end of 2015. 

Based upon the additional work related to the Round Lake FS, and assuming the need for a sediment removal remedy for Round Lake, construction completion for the site is expected to take place in fiscal year 2018.

Success Story

The South Plume (Operable Unit 3 [OU3]) has receded to the point where the Plume Groundwater Recovery System (PGRS) extraction well is no longer needed for remediation purposes.  The well has been shut down and the shutdown made permanent through the recent Operable Unit 3 ROD Amendment.

The New Brighton Contaminated Groundwater Remediation System (NBCGRS), the remedy for the large North Plume of contaminated groundwater (Operable Unit 1), continues to operate as an effective gradient control system.  Groundwater monitoring indicates that, generally, the contaminant plume continues to decrease in both concentration and size.

With the completion of the on-site (on-TCAAP) cleanup and placement of remedies, cleanup of the New Brighton/Arden Hills/TCAAP Superfund Site is almost completed.  Final completion will occur when a remedy for Round Lake has been selected and implemented.

Community Involvement

The communities surrounding TCAAP have been, and continue to be, active in both the CERCLA cleanup and the property transfer issues at the Site.  A restoration advisory board (RAB) formed pursuant to Department of Defense guidance, composed of citizens from the local communities and charged with providing public input into the Army's cleanup of the Superfund Site, has been active since its inception in 1996.

The City of New Brighton has been an integral partner with the Army in the successful implementation and operation of the OU1 and OU3 groundwater extraction and cleanup remedies because it is the City's municipal wells which are serving, or have served, as the extraction wells for these remedies.

As of early 2015 1,4-dioxane has been found in the water supply of the City of New Brighton at concentrations above the Minnesota Health Risk Level for that contaminant.  This discovery impacts the ability of the City of New Brighton to continue to operate its water supply wells for the remediation purposes documented in the OU1 ROD.  The duration of this impact is currently unknown.  The stakeholders to the issue (New Brighton and neighboring communities, U.S. Army, USEPA, MPCA, Minnesota Department of Health) have discussed how to proceed to address the issue.  As of mid-2015, the Army is planning to collect groundwater samples and analyze them for 1,4-dioxane throughout the groundwater monitoring network so as to determine the nature, extent and magnitude of 1,4-dioxane contamination in the TCAAP on-site and off-site groundwater plumes.

Congressional Interest

The Minnesota Congressional delegation continues to follow the progress of cleanup and property transfer at the Site.  In the mid-1990's then Congressman Bruce Vento led a public dialogue which resulted in a redevelopment plan for TCAAP ("the Vento Plan").  The Vento Plan has provided the framework for subsequent redevelopment efforts.

In the spring of 2014 USEPA, MPCA and USFWS met with Congresswoman Betty McCullom and members of her staff to update the community on the status of the Round Lake Feasibility Study.



Property Reuse

Of the approximately 2400 acres of TCAAP, control over 1500 acres has been transferred to the U.S. Army Reserve and the Minnesota National Guard.  Smaller portions have been transferred to Ramsey County for a public works facility and a wildlife corridor, and the City of Arden Hills for a new City Hall.  Approximately 660 acres was authorized by the United States Congress to be excessed and is currently in the process of being transferred for redevelopment purposes.

In April 2013 the Army transferred 387 acres of the former TCAAP to Ramsey County, which intends to redevelop it for multiple uses.  A groundbreaking ceremony to kick off the redevelopment process was held on June 7, 2013.


Remedial Project Manager, U.S. EPA
thomas barounis (barounis.thomas@epa.gov)
(312) 353-5577





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