The D’s Fabric Care property, located at 12 Second Street in Cloquet, was referred to the MPCA Superfund program based on findings from a 2012 site assessment. Perchloroethylene (PCE) was detected in groundwater samples collected during a petroleum leak site investigation on an adjoining property. The D's Fabric Care property was a dry cleaning business from 1966 to 1995.
What's the problem?
The 2012 investigation confirmed that high concentrations of PCE solvent vapor are present under the D’s Fabric Care building (the highest concentration was 1,070,000 µg/m3), and appear to originate from near the former dry cleaning machinery. PCE is also present in shallow groundwater beneath the site and has been detected in water discharging from an on-site basement sump.
Groundwater contaminated with PCE can release vapors back into the soil which can intrude into nearby buildings and pose health risks to the people living and working in them. In this case, the D's building, an old gas station on an adjoining property (designed by Frank Lloyd Wright), and nearby residences may be at risk for vapor intrusion. The site has also been discharging contaminated sump water to the municipal sanitary sewer system, and there's a risk that contaminated groundwater will migrate off site (including to the St. Louis River, located about 1,000 feet to the north).
The MPCA hired a contractor to investigate the site beginning in April 2012, which included soil, groundwater and soil-gas sampling. The highest concentration of PCE in groundwater (84.1 µg/L) was detected in the sump sample collected from the basement of the D’s building. Groundwater samples collected throughout the site had PCE exceeding the Minnesota Department of Health (MDH) established health risk limit for drinking water.
Sub-slab samples from the D’s building exceeded by 10 times the industrial intrusion screening value (ISV) of 30 µg/m3 for PCE, and soil-gas samples collected throughout the property noted the presence of PCE at concentrations exceeding the current residential ISV of 2 µg/m3. To date, the full extent and magnitude of soil, groundwater and soil-vapor contamination has not been identified.
The MPCA is currently working with the owners of the D’s and gas station buildings to install active mitigation systems. The MPCA has also retained a multi-site contractor to install sub-slab vapor points in seven nearby residences, and evaluate if soil-vapor intrusion is occurring at these properties. Sump discharge to the sanitary system is not allowed under Cloquet's city code, so the matter has been referred to the Western Lake States Sanitary District for regulatory oversight.
Possible health effects
Elevated levels of PCE in the soil gas in the vicinity of the D’s Fabric Care site constitute a significant health risk. PCE has been detected in soil gas at levels more than 35,000 times the regulatory values for commercial properties in this area. In addition to the vapor intrusion risk to the onsite buildings, the soil vapors may be harmful to those who would excavate soil or work in areas below grade.
Vapor intrusion occurs chemical vapors seeping 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 the most likely to be affected.
Site Remediation and Redevelopment Section