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. At this time all land has either been transferred or leased out.
Army Ammunition Plant in Minnesota
Public involvement
The most recent TCAAP Restoration Advisory Board (RAB)’s meeting was an in person and virtual meeting on Sep 15, 2026. Additional RAB meeting information including the slides that were presented and meeting minutes when available is located in Restoration Advisory Board (RAB).
The Army is hosting the next RAB meeting on Feb 15, 2027, at 7:00 p.m. CST, to update the community on the latest status of cleanup at TCAAP.
The RAB meeting will be held virtually on MS teams. If you’d prefer you can also dial into a teleconference line. Further information, including the meeting invitation, will be updated when available.
The RAB meeting is open to the public. Anyone interested in or wanting information about the TCAAP cleanup activities is invited to attend.
If you are interested in serving on the RAB, please let us know.
Cathy Kropp, Environmental PA Specialist
Phone: 443-243-0313
Email: Cathryn.L.Kropp.civ@mail.mil
More information about the RAB is available here.
Cathy Kropp, Environmental PA Specialist
Phone: 443-243-0313
Email: Cathryn.L.Kropp.civ@mail.mil
More information about the RAB is available here.
Recent Updates
Following the signing of the Round Lake Record of Decision (ROD) in 2022, dredging of the lake commenced in June 2026 and will continue through approximately October 2027. This dredging action is expected to remove approximately 76,000 cubic yards out of the estimated 156,000 cubic yard volume that is required to be removed to meet the cleanup levels established in the ROD. A second dredging contract will be awarded after the conclusion of the current contract pending resource availability.
The Army will continue to monitor groundwater through sampling and continue funding and operation of groundwater treatment systems 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 has taken actions to optimize the two treatment facilities to ensure they are operating as efficiently and effectively as possible. Most recently with the addition of the Source Groundwater Recovery System (SGRS) in 2023 to treat OU2, and with the funding and installation of an additional well in 2026 at OU1.
The permanent granular activated carbon Water Treatment Facility in New Brighton (OU1) and the TCAAP groundwater remediation system (TGRS at OU2), that were the primary treatment components of the original remedies, were not capable of removing an emerging chemical of concern (1,4-dioxane) to levels protective of public health. Therefore, the Army added a supplemental process to each system to treat 1,4-dioxane. An explanation of significant differences (ESD) was published to document these changes and is available on the resources page.
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 on the resources page
What’s Next?
The next stakeholder meeting will be held on Feb 15, 2026. These meetings are more technical in nature than the RAB meetings but often discuss the same topics.
Dredging operations at Round Lake will continue through approximately October 2027, pausing during the winter months when weather prevents activity.
At OU1, the Army will abandon three industrial wells and reinstall four monitoring wells. At OU2, the Army will complete abandonment of four monitoring wells, reinstallation of one monitoring well, optimize the monitoring well network, and conduct risk assessment for more unrestricted land use. The Army has completed optimization of the TCAAP Groundwater Recovery System (TGRS) for OU2, including constructing and operating the Source Groundwater Recovery System (SGRS) and modifying the Boundary Groundwater Recovery System (BGRS). Together these two systems comprise the TGRS. The Army will continue annual groundwater monitoring of OU3.
The FY23, FY24, and FY25 APRs are currently delayed in the finalization and review process due to significant changes being made in the report format, these reports are expected to be finalized sequentially by Spring of 2027 and will be uploaded to the RAB website once completed.
Where can I get more information?
Any questions or concerns may be directed to the Army Remedial Project Manager:
Thomas P. Toudouze
U.S. Army Environmental Command
West, Central America, and Pacific Division
Fort Sam Houston, Joint Base San Antonio, Texas
Cell – (210) 823-6980
Office – (520)-674-1984
E-mail – thomas.p.toudouze2.civ@army.mil