The Pure Oil Bulk Storage Facility site is located at 352 3rd Street in Excelsior and was formerly used for bulk oil storage. The MPCA is addressing petroleum contamination on the site and, in 2013, detected the chlorinated solvents perchloroethylene (PCE) and trichloroethene (TCE) in groundwater and soil vapors.
What's the problem?
The site's groundwater PCE concentrations were 9.74 ug/l, which were above the Minnesota Department of Health’s (MDH) health risk limits for drinking water of 4ug/l. PCE soil vapor concentrations on the site are 100 times higher than the MPCA’s intrusion screening value (ISV) for commercial/industrial land; the highest concentration was 2,200 ug/m3.
In 2015, PCE levels in two groundwater-monitoring wells were almost twice the MDH’s limits for drinking water, and soil vapor samples again detected PCE and TCE. TCE detected in one sub-slab sample was above the MPCA’s ISV for commercial/industrial land use. PCE sub-slab concentrations below one of the buildings were 100 times greater than the same ISV; the highest PCE sub-slab concentration was 102,000 ug/m3. The full extent and magnitude of groundwater and soil vapor contamination has not been defined.
After reviewing the data, the MDH issued an expedited action determination for one of the buildings at the site to mitigate the immediate vapor intrusion risk to building occupants. A sub-slab depressurization system is being installed in the building with the highest PCE sub-slab concentration.
Possible health effects
Vapor intrusion occurs when chemical vapors seep from contaminated groundwater through the soil and into buildings. The vapors can degrade indoor air, sometimes to the point of affecting human health. Recent research shows that volatile organic compounds (VOCs) entering homes as vapor may be more harmful than previously thought.
As a result, the MDH has recommended lowered intrusion screening values (ISVs) for several VOCs, including PCE. Long-term inhalation exposure to PCE may cause symptoms such as impaired cognitive performance and adverse effects to the kidney, liver and immune system. Sensitive populations including pregnant women, infants and young children, elderly people, or those with chronic diseases are among those most likely to be affected.
Site Remediation and Redevelopment Section