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 RAB’s last meeting was a virtual meeting on Jan. 14, 2021.

The Army is hosting a public meeting on Feb. 16, 2021 at 7:00 p.m. CST to elect a community co-chair, review and finalize the operating procedures, and review and finalize membership. This meeting is being conducted virtually to maintain social distancing and protect the health of the community during the Coronavirus Disease 2019 (COVID-19) public health emergency.

The purpose of the meeting is TCAAP RAB administration. Because it was only one month since the last meeting, the Army will NOT provide an update on the cleanup program at the former TCAAP. The meeting is open to the public. Anyone interested in participating on the TCAAP RAB or wanting information on the TCAAP cleanup program is invited to attend.

The meeting will be held on MS teams. You do not need to download the software to participate; you can access the meeting through your web browser. If you’d prefer you can also dial into a teleconference line. Please contact Cathy Kropp at 443-243-0313 or for information on how to access the meeting via internet or phone.

The meeting Agenda, draft minutes from the January meeting, RAB mission statement and draft Revised Operating Procedures can be downloaded below before the meeting:

The meeting Agenda and three briefings can be downloaded below before the meeting:

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?

The Army is working to optimize the two treatment facilities at OU1 and OU2.  TheNew Brighton Contaminated Groundwater Recovery System at OU1 and the Source Groundwater Recovery System at OU2 are being evaluated to increase mass removal from groundwater.  Implementation of these optimization efforts are planned for spring/summer 2021. 

We held a stakeholder’s call to provide a project update on October 15, 2020 and copy of the presentation is found here

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