The 430-acre parcel of land in Arden Hills, where the Vikings want to build a new football stadium, is also part of the state's largest Superfund site. That means the land and groundwater are polluted and will need more cleanup before a stadium can be built there.
The contamination of the soil and groundwater occurred when the now-defunct Twin Cities Army Ammunition Plant operated on the site from 1941-1981.
The soil within the plant boundaries was contaminated with solvents, semivolatiles, metals and PCBs. Other areas within the site were used as dumps.
Some of the industrial waste spilled into the storm sewer system into Round Lake, contaminating the lake sediment with heavy metals and PCBs.
Hans Neve supervises the Brownfield Program for the Minnesota Pollution Control Agency.
"As you can guess, lead is one of the contaminants at the site," Neve said. "Also, in the manufacturing process they used a type of industrial solvent called TCE, or trichloroethylene, that's also a contaminant at this site."
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The U.S. Army is responsible for the Superfund site, which is technically known as the New Brighton/Arden Hills Superfund Site.
The cleanup process began in 1987 when the Army, EPA, and the Minnesota Pollution Control Agency entered into an agreement for the investigation and remediation of the site. The Army has overseen many efforts since then to clean up the site and prevent further contamination.
The MPCA's Neve said developers have plenty of experience cleaning up so-called "brownfield" sites like the one at Arden Hills. Neve says both TCF Bank Stadium and Target Field were built on brownfield sites.
The EPA estimates that most of the cleanup has been completed. The final major project remaining is to clean up the contamination of Round Lake.
(MPR's Cathy Wurzer contributed to this report.)