The Lyndale Avenue Corridor site is generally located approximately three blocks east and west of Lyndale Avenue between 83rd Street and 98th Street in Bloomington, Minn. The site is primarily commercial and industrial properties bordered by residences on the east and west sides. Several businesses in the corridor, including manufacturing, vehicle repair and dry cleaning facilities, have used or are currently using hazardous chemicals. Investigation activities have occurred at more than 40 properties and have identified contamination along this Lyndale Avenue corridor.
What's the problem?
The primary contaminants of concern are trichloroethylene (TCE) and perchloroethylene, also known as perchloroethylene (PCE). TCE and PCE are solvents used for metal cleaning and other industrial processes. PCE is also commonly used in dry cleaning. Both compounds have the potential to cause long term health risks. 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 2009, a property located at the northeast corner of 35W and 94th Street was referred to the MPCA when volatile organic compounds (VOCs) were found in the groundwater. The agency finished an internal review of contaminated properties in the Lyndale Avenue Corridor area in 2010. Further investigation and study in 2012 and 2013 helped define the extent of PCE and TCE contamination in groundwater and also potential vapor intrusion risks.
The highest VOC concentrations detected during groundwater were 1,000 ug/l PCE and 230 ug/l TCE, which was above the Minnesota Department of Health's (MDH) health risk limit of of 5 ug/l for both chemicals in 2013. No drinking water wells have been impacted from the site to date. The highest PCE soil vapor concentration found was 3,850 ug/m3, approximately 2,000 times the MDH established vapor intrusion screening value (ISV) for residential properties (2 ug/m3).
Since 2014, sub-slab soil vapor samples were collected from 12 homes and 9 commercial properties. Eleven residential and 7 commercial properties had soil vapor concentrations at or above the screening criteria. The highest sub-slab PCE concentration found in a home was 19,200 ug/m3 (approximately 10,000 times the ISV). The highest PCE concentration below a commercial property was 186,000 ug/l (93,000 times the ISV). Vapor mitigation systems have been installed at 9 residential properties to date. Three commercial properties are in the process of having mitigation systems installed.
During the winter and spring of 2017, the MPCA is attempting to get access to sample an additional 11 residential properties and 17 commercial properties. Additional vapor mitigation will likely be needed in several commercial properties once additional funding is obtained.
Based on the soil vapor and groundwater data, there appears to be multiple sources of VOC contamination in the area. The sub-slab vapor investigation is being expanded to include single- and multiple-family homes on the north side of 92nd Street between Lyndale and Bryant Avenue.
Possible health effects
Vapor intrusion occurs as 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 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 the immune system. Sensitive populations including pregnant women, infants and young children, elderly people, or those with chronic diseases can be affected.