The Environmental Protection Agency (EPA) has partially delisted the former Twin Cities Army Ammunition Plant in northern Ramsey County from its Superfund National Priorities List after more than three decades of study and cleanup.

The soil at the 2,370-acre TCAAP site has been delisted, or removed, from the Superfund list, the federal agency announced this week. Delisting occurs when “all cleanup goals have been achieved” and “no further cleanup is required to protect human health or the environment,” according to the EPA.

The Minnesota Pollution Control Agency (MPCA) is expected to remove TCAAP’s soil from its state Superfund list later this fall. TCAAP was added to the federal Superfund list in 1983.

“This was a 30-year process. This is a really important milestone,” said Amy Hadiaris, a hydrogeologist and supervisor with the MPCA.

However, groundwater at the site is still contaminated and will remain on the state and federal Superfund lists while the Army continues those cleanup efforts, expected to take years.

Federal and local agencies, including Ramsey County, have spent millions in pollution remediation over decades at the TCAAP site.

“The north metro has been waiting a long time to get this site cleaned up, and this delisting is another step closer to making it a reality,” MPCA Commissioner Laura Bishop said in a statement.

Before delisting the site, the EPA held a 30-day comment period this summer but did not receive any feedback.

Soil delisting is a critical step for redeveloping 427 acres of the property acquired by Ramsey County in 2013. It helps the public understand that the county’s acreage is safe for use and ready for new homes and businesses.

“It’s a milestone that should be celebrated,” said Martha Faust, Ramsey County’s redevelopment manager. “The county has put a lot of time and energy into trying to reclaim this site.”

Once farmland, the site was chosen for the immense ammunition plant built by the Army in 1941, the same year the U.S. entered World War II. At its peak, the plant included more than 300 buildings and employed 26,000 people.

Ammunition manufacturing continued through the Korean and Vietnam conflicts. Other manufacturers later leased space at the site to make fuses, ammunition and other industrial items.

“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,” according to the MPCA.

The manufacturing processes and methods of disposal contaminated “groundwater, soil, sediment, and to a lesser extent surface water.” Soil contaminants included volatile organic compounds and lead.

The Army, working with the EPA and MPCA, identified water and soil contamination and cleaned the soil to industrial standards over the years. The Army still owns a large piece of that land and leases it to the Minnesota National Guard.

Ramsey County has spent $40 million on acquiring the land, building infrastructure and cleaning up the site to make it suitable for residential use. Over a period of nearly three years, crews removed more than 400,000 tons of concrete and asphalt, nearly 10,000 tons of PCB hazardous waste, more than 7,000 tons of asbestos-containing soil waste and nearly 100,000 tons of non-hazardous impacted soil. Much of the concrete and materials, including old rail lines, were recycled or reused.

The MPCA certified additional remediation work in 2016. Along with the EPA’s delisting, that “confirms that the soil on the site has been remediated to residential standards,” Faust said. “There is no barrier to the timely redevelopment of this property.”

Any future development on the site would be connected to St. Paul’s water system, which comes from the Mississippi River.

Hadiaris said it was important to understand that not all 2,300 acres of soil on the TCAAP site was contaminated. “There were specific source areas across TCAAP. All of those areas have been addressed,” she said.

Now the biggest barrier to development is the strained relationship between landowner Ramsey County and the city of Arden Hills. The county has sued Arden Hills over plans for the site; the county wants denser development of up to 2,500 homes with more affordable housing, while city leaders want it capped at 1,460 housing units.