Twin Cities Army Ammunition Plant


Landscape with trees and water

Welcome to the website for the former Twin Cities Army Ammunition Plant (TCAAP). The former TCAAP is located in the city of Arden Hills in the northern portion of the Minneapolis – St. Paul metropolitan area in Ramsey County. It is surrounded by the cities of New Brighton, Arden Hills, Mounds View, and Shoreview, Minnesota. TCAAP formerly occupied a four-square mile area east of U.S. Interstate Highway 35W and north of Ramsey County Highway 96.

Previous manufacturing operations from 1942 to 1981 impacted soil, groundwater, sediment, and surface water, and the former TCAAP was placed on the National Priority List (NPL) in September 1983 and designated as the New Brighton/Arden Hills (NB/AH) Superfund Site. Cleanup at the former TCAAP is taking place under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) with the United States Army as the lead agency in coordination with the United States Environmental Protection Agency (U.S. EPA) Region 5 and the Minnesota Pollution Control Agency (MPCA).

The size of the former TCAAP has shrunk over time because of property ownership transfers and reassignment of control to the National Guard Bureau, Army Reserve, Ramsey County, and the City of Arden Hills. The remaining land (approximately 160 acres) is in the process of being transferred out of federal ownership.

Map showing Former Twin Cities
Army Ammunition Plant in Minnesota

Photograph of former manufacturing
facility at the TCAAP

Public Involvement

The Army established a Restoration Advisory Board (RAB) at the former TCAAP in 1996. A RAB is a partnership between the surrounding community, the Army, the State, and the USEPA that provides a forum for discussions to increase community understanding and support for cleanup efforts. It helps with improving the soundness of government decisions and ensuring cleanups are responsive to community needs. The RAB’s last meeting was in 2015. The Army has been contacting former RAB members to see if they are interested in continuing to serve on the RAB. The Army published a solicitation for RAB members on the following publications and dates listed below and is still seeking volunteers to serve on the RAB.
If you are interested in serving on the RAB, please let us know.
Cathy Kropp, Environmental PA Specialist
Phone: 443-243-0313
More information about the RAB is available here.

Recent Updates

The Army will continue to monitor groundwater through sampling, and operate and fund groundwater treatment at New Brighton (known as OU1) and Arden Hills (known as OU2) until the levels are within state and federal standards for safe drinking water.

The Army is currently working on plans to optimize the two treatment facilities to ensure they are operating as efficiently and effectively as possible. Optimization sampling is available in Environmental Protection Agency.

Many actions have been performed to address affected soil and groundwater at the NB/AH Superfund Site, including source removal; groundwater treatment; capping; soil treatment with an in-situ volatilization system; and soil incineration. The groundwater plumes in Operable Unit (OU) 1 and OU 3 are monitored annually by a network of nearly 300 monitoring wells.

Annual Performance Reports (APRs) and Five Year Review Reports are published by the Army to summarize the status of remedy implementation and to address remedy performance at the NB/AH Superfund Site. You may access the most recent APR and Five Year Review Report at the links below:

What’s Next?

When design plans are approved to optimize the two treatment facilities at New Brighton and Arden Hills, they will be available for public review here. The Army is committed to ensuring treatment is as efficient and effective as possible.

The Army is working with EPA, MPCA, MDNR and USFWS to finalize a feasibility study to address contamination in Round Lake (known as TCAAP-31) which is affecting benthic organisms in the lake but does not pose a risk to human health. Once final, that report will be shared with the public here.

Where can I get more information?

Any questions or concerns may be directed to the:

  • Mail:
    U.S. Army Environmental Command
    Attn: Mail Stop 112, IMAE-E
    2455 Reynolds Road
    JBSA Fort Sam Houston, TX 78234-7588