In November, the Minnesota Department of Health (MDH) and Minnesota Pollution Control Agency (MPCA) sent a joint letter to owners and occupants of residences in part of the Como neighborhood of southeast Minneapolis to alert them to an ongoing investigation of harmful trichloroethylene (TCE) vapor from contaminated groundwater and soils that may be intruding into their homes. TCE is a commonly used cleaning solvent and degreaser.
Sadly, the confusing messages in the letter attempt to inform residents that although there may be no immediate or urgent health concern, more investigation and testing needs to take place in their residences to evaluate actual risk and determine the correct response.
The soil vapor of concern, trichloroethylene, commonly known as TCE, was used as an industrial solvent at a former General Mills, Inc., research facility at 2010 E. Hennepin Ave in Minneapolis until at least the 1960s. During that time, waste TCE was illegally disposed of in a pit on the property. The contaminated site has been known for more than 30 years. Under the oversight of the MPCA, pumped and treated groundwater for 25 years at the Hennepin Avenue site to remove the TCE. Based on groundwater testing over the years, data demonstrated that TCE concentrations in the groundwater significantly declined and the groundwater plume had stabilized. With approval from the MPCA, the treatment systems were prematurely shut down in September 2010 and monitoring was increased to determine whether the system can remain shut down; this was a gross error.