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New Brighton/Arden Hills Superfund Site (a.k.a.Twin Cities Army Ammunition Plant or TCAAP)

The New Brighton/Arden Hills Superfund site, which is comprised of the Twin Cities Army Ammunition Plant  and its associated property, is a federal Superfund site located in Arden Hills, Minnesota. 

Contamination resulting from past ammunition manufacturing operations at the facility has been identified in groundwater, soil, sediment and surface water. The U.S. Army, U.S. Environmental Protection Agency (EPA), and the MPCA have worked jointly to determine the contaminants involved, the extent of the contamination, and the cleanup that is required.

What's the problem?

TCAAP operated for several decades during a time when there were no laws governing disposal of chemicals. During these years, the Army generated industrial wastes that were disposed of using accepted practices of the times, which included on-site dumping, burial, and open burning. The manufacturing processes and historical disposal areas at the facility caused contamination of groundwater, soil, sediment, and to a lesser extent surface water.

The Army, EPA, and MPCA have worked jointly to discover the extent of contamination and to clean up pollution that poses a risk to human health and the environment, based on the current land use.

Overview

Contaminants of concern

Chlorinated solvents and lead are the primary contaminants in the soil. PCBs (polychlorinated biphenyls), PAHs (polynuclear aromatic hydrocarbons), and petroleum compounds are also present in soil in some areas. While explosive materials and radionuclides were used at TCAAP, concerns about their possible presence in soil have been resolved through investigation and cleanup. The primary contaminants of concern in the groundwater are chlorinated solvents.

What's already been done

  • More than 94,000 cubic yards of contaminated shallow soil have been remediated to Army industrial use cleanup standards, a set of site-specific standards.
  • More than 200,000 pounds of chlorinated solvents have been removed from the deep soils
  • Approximately 1,500 cubic yards of PCB-contaminated soil have been incinerated.
  • Approximately 1.2 billion gallons of groundwater are treated each year.
  • Approximately 226,000 pounds of chlorinated solvents have been removed from the groundwater.

Current land use controls restrict property use to "Army industrial."

What's left to do

  • Groundwater treatment is expected to continue until approximately 2040. The Army will continue to operate and pay for groundwater treatment, even if part of the property is sold.
  • While the historical waste disposal areas have all been addressed, some areas of soil contamination, particularly under existing buildings, require additional investigation and possible cleanup. The best time to complete this task is when the buildings are demolished.

Can the site be safely redeveloped?

Previous soil investigations at TCAAP under the Superfund program were not intended to prepare the property for redevelopment. Additional investigation and clean up of soil could be necessary if the property use is to change.

The MPCA's Voluntary Investigation and Cleanup Program and Petroleum Brownfields Program will work with any new owner/developer to ensure that the site is safely redeveloped. The assessment and cleanup is fairly straightforward and has been done before on many contaminated properties. For more information about sites that were cleaned up and redeveloped in partnership with the Voluntary Investigation and Cleanup Program and Petroleum Brownfields Program, visit the Brownfields Success Stories webpage.

Contacts

 

For more information

Description

The Twin Cities Army Ammunition Plant (TCAAP) was constructed between 1941 and 1943. Before that time, the site was used primarily as farmland. During a 16-month period and at a cost of $73 million, more than 300 buildings were built at the site. In early 1942, the manufacture of small arms ammunition and other related materials began.

The site continued to grow into a self-contained community with 40 miles of electric and telephone wire, 83 miles of sewer, and 37 miles of road and railroad track. At its peak, the plant employed approximately 26,000 people, primarily manufacturing ammunition for WW II and, subsequently, the Korean and Southeast Asia conflicts.

Over the years, there have been numerous tenants, most of whom performed non-military activities. Since the late 1950s, Alliant Techsystems (ATK), a potentially responsible party for the site, manufactured fuses and selected ammunition at the facility. ATK recently relocated to a site outside Minnesota.

Environmental studies began at TCAAP in 1978 with a records search of past operations to determine if a significant potential hazard existed for contamination migrating from the facility. In 1981, solvents were discovered in groundwater wells beyond the TCAAP boundary, including the city of New Brighton’s municipal water supply. TCAAP was considered as the likely source of the contamination.

In that same year, TCAAP was added to the Army’s Installation Restoration Program. In 1983, the site was placed on the federal National Priorities List as the New Brighton/Arden Hills Superfund site, with a Hazard Ranking Index score of 59.6. Federal funding to begin the cleanup became available in 1983. A three-party Federal Facility Agreement (FFA) between the Army, the MPCA, and the EPA was signed in December 1987, the first such agreement nationwide. The FFA is the regulatory driver for the cleanup at the site. Under this agreement, significant cleanup has been conducted by the Army, with regulatory oversight provided by the MPCA and EPA.

Problem

Contamination resulting from past ammunition manufacturing operations at the facility were identified in groundwater, soil, sediment and surface water. Contaminants of concern included chlorinated solvents, explosives, metals, volatile organic compounds, polychlorinated biphenyls, poly-aromatic hydrocarbons, and lead.

The primary contaminants of concern in the groundwater both on- and off-site are VOCs. Read more about these issues in the Off-site groundwater plumes at the New Brighton/Arden Hills Superfund Site fact sheet.

The contaminants in the soil at the New Brighton/Arden Hills Superfund site primarily consist of VOCs and lead. The contaminated sites that are being addressed by the Army consist of groundwater and surface water, surface disposal areas, sediments, disposal pit/dry wells, landfills, chemical disposal areas, firing ranges, unexploded munitions/ordnance, and burn areas. The Army, EPA, and MPCA have worked jointly to determine the contaminants involved, the extent of the contamination, and the cleanup that is required.

Environmental restoration

Map of the Twin Cities Army Ammunition Plant (TCAAP)Map of the TCAAP Site and Surrounding Communities

Within the former TCAAP property, there are 20 active sites and eight sites that have been cleaned up. There are seven contaminated groundwater sites, one contaminated sediment site, two landfill sites, two firing range sites, two unexploded munitions/ordnance sites, two surface disposal areas, one disposal pit/dry well site, three chemical disposal sites, one small arms range site and four burn area sites. The Superfund site has been divided into three work areas: Operable Unit 1 (the off-site North Groundwater Plume); Operable Unit 2 (the on-site contamination) and Operable Unit 3 (the off-site South Groundwater Plume).

A number of actions have been taken to remove contamination at New Brighton/Arden Hills Superfund site. These include source removal; groundwater treatment; capping; soil treatment with an in-situ volatilization system, and soil incineration. To date, more than 94,000 cubic yards of contaminated soil have been treated to meet Army industrial use standards. More than 200,000 pounds of VOCs have been removed from deep soils, and the Army has successfully completed extracting VOCs from soils using soil vapor extraction systems. Approximately 1,500 cubic yards of PCB-contaminated soil have been incinerated. Approximately 1.2 billion gallons of groundwater are treated each year with more than 35.5 billion gallons of groundwater having been treated to date. Approximately 226,445 pounds of VOCs have been removed from the groundwater. Current land use controls restrict property use to "Army industrial," a site-specific standard. 

What's left to do?

  • Groundwater treatment is expected to continue until approximately 2040. The Army will continue to operate and pay for groundwater treatment, even if part of the property is sold.
  • While the historical waste disposal areas have all been addressed, some areas of soil contamination, particularly under existing buildings, require additional investigation and possible cleanup. The best time to complete this task is when the buildings are demolished.

The site is scheduled to be delisted from the NPL in 2040.

Community involvement

TCAAP has an active community involvement group — the TCAAP Restoration Advisory Board — which was established in 1996. It consists of both community and non-community members. The RAB has two active committees: a Technical Committee that reviews and comments on technical documents, and a Communication/Membership Committee that recruits RAB members and helps keep the community informed.

The RAB has provided input on past cleanup decisions and is continuing to monitor activities at the site. The RAB has a website and the members have helped to communicate restoration activities to interested stakeholders in the early land transfer process through review of technical documents and participation in stakeholder meetings.

A TCAAP Community Relations Plan is also in place. TCAAP also distributes a periodic newsletter to update the public on current restoration activities and milestones.

Land transfer

The former TCAAP property encompasses approximately four square miles or 2,370 acres of land. Of this, 1,521 acres have been reassigned to the National Guard Bureau (in 2000 and 2002); 6.9 acres have been transferred to the city of Arden Hills for a new city hall (2001); 112 acres have been transferred to Ramsey County as part of the Rice Creek corridor (2005); and 37 acres have been transferred to Ramsey County for a multiple-use facility (2005). More than 600 acres were declared excess by the Army in 2002. The excess property is proposed for transfer, via auction, through the U.S. General Services Administration.

Natural resources/wildlife management

Approximately 1,700 acres on TCAAP consist of significant natural resources, including 188 acres of forest, 120 acres of glacial hills and mounds, 338 acres of prairie complex, the 560-acre Marsden Lake wetland, the 12-acre Sunfish Lake, and ¾ of a mile stretch of Rice Creek. The Minnesota Department of Natural Resources, the Audubon Society, the University of Minnesota, and other local organizations have volunteered expertise and time for wildlife management at TCAAP. Projects include prairie restoration, a bluebird recovery program, a wood duck nesting program, walleye rearing in Sunfish Lake, and deer herd management.

After the reintroduction of trumpeter swans to Marsden Lake, TCAAP became the first Ramsey County site in 150 years where cygnets were hatched. One can see bluebirds, wood ducks, swans, and white tailed deer on TCAAP, as well as red fox and one of Minnesota’s threatened species, the Blanding Turtle, whose species and habitat are both protected under TCAAP’s Wildlife Management Program.

Where to from here

Ecological feasibility studies focusing on Round Lake and Pond G are in process. Although the groundwater treatment system for Operable Unit 3 has been terminated and the OU3 plume is being monitored, groundwater pumpout and treatment of the OU1 plume continues. Also, an active groundwater remedy is still in place at Site K. Five year reviews will continue to be performed as long as the site has not been cleaned up to residential use standards. The land transfer process continues to be under discussion and additional cleanup associated with potential different uses for the property may be required.

Assigned staff

MPCA

U.S. Army

Mike Fix, 651-294-4930

U.S. Environmental Protection Agency

Tom Barounis, 312-353-5577

Related links

 

Last modified on June 06, 2014 10:51