MN Warns of Solvent Vapors in Homes


Industrial solvent vapors from contaminated groundwater at an old Superfund site may be intruding into homes and properties in southeast Minneapolis, state officials have announced.

In a joint letter Wednesday (Nov. 6), the state's Department of Health (MDH) and Pollution Control Agency (MPCA) notified area residents and owners of "an environmental investgation in your neighborhood over the next several weeks."

The investigation will examine whether underground vapors from contaminated groundwater at the seven-acre General Mills/Henkel Corp. Superfund Site are entering homes and buildings. General Mills Inc. will conduct that investigation under MPCA's supervision.

"Some of the groundwater in the area is contaminated and could release vapors that can rise through the soil and seep through basement and foundation cracks into indoor air," the letter said.

Site History

The problem stems from a site that GMI used for food research from 1930 to 1977. From 1947 to 1962, GMI dumped about 1,000 gallons of solvents in a soil absorption pit on the property.

In the early 1980s, the solvent tricholoroethylene (TCE) was discovered in local soil and groundwater, and three perforated 55-gallon drums of waste were found buried 10 to 12 feet below the surface of the site, MPCA reported in a Fact Sheet.

GMI, as the responsible party, removed drums and piping from the pit in 1981. The site was added to the federal Superfund list in 1984. Beginning in 1985, the affected groundwater was pumped out and treated. Since then, GMI has monitored the plume of contamination in the groundwater, and state officials say it is not spreading.

The groundwater pump-out system was shut down in September 2010, after the state determined that TCE concentrations declined below the cleanup action levels.

GMI Site Map

About 1,000 gallons of solvents, mainly TCE, were dumped at the seven-acre General Mills site in Minneapolis from 1947 to 1962. The site now has homes and businesses.

The Environmental Protection Agency considered the site a Superfund success story, boasting in 2007 that part of it had been redeveloped as an incubator for more than 130 businesses.

Contamination Continues

Now, however, the state says some of the groundwater is still contaminated and could release TCE vapors through basement and foundation cracks into buildings, where it could be inhaled by occupants.

“We know the contamination is in the vapor under the ground,” Hans Neve, a supervisor with MPCA's Superfund program, told the Minneapolis Star Tribune. “Is it getting into the homes? That’s the question we need to answer.”

If vapor intrusion is occurring, concentrations are likely to be higher in basements than on upper floors. Unborn children, infants, children, pregnant women and people with impaired immune systems are considered at the greatest risk from exposure.

Sampling and Remediation

The agencies have scheduled public meetings for Tuesday (Nov. 12) and are asking residents and property owners in the affected areas to sign an access agreement to allow sampling on their property. Testing will begin by Nov. 18 with residents' permission, the state says.

Superfund Brochure

EPA considers the old General Mills research site a model of reuse. More than 130 businesses operate there.

Homes found to have excessive levels of TCE in their soil gas will receive a sub-surface vapor ventilation system installed by GMI.

The systems consist of a hole in the building floor, with an attached sealed pipe that leads to a low-wattage fan in the attic or outside the building. The fan pulls vapors from beneath the floor and discharges them to the atmosphere through a stack on the roof, the agencies said.

Minneapolis-based General Mills, one of the world's largest food companies, vows to remediate any problems.

“We predate the state, we predate the city of Minneapolis,” company spokesman Tom Forsythe told the Star Tribune.

“We’re going to address this issue in our hometown, and we’re going to make it right.”


Tagged categories: Adaptive reuse; Building envelope; Commercial Buildings; Environmental Protection Agency (EPA); Hazardous waste; Henkel Corp; Maintenance + Renovation; Solvents

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