The Lyndale Avenue Corridor site is located approximately three blocks east and west of Lyndale Avenue South between 90th Street and 96th Street in Bloomington, Minn. The site is primarily commercial and industrial properties bordered by residences on the southeast side and west side. Several businesses in the corridor, including manufacturing, vehicle repair and dry cleaning facilities, have used or are currently using hazardous chemicals. Investigation activities in Bloomington have identified contamination in the groundwater and soil vapor along the Lyndale Avenue Corridor.
What's the problem?
The primary contaminants of concern are trichloroethylene (TCE) and tetrachloroethylene (PCE), also known as perchloroethylene or perc. TCE and PCE are solvents used for metal cleaning and other industrial processes. PCE is also commonly used in dry cleaning.
Groundwater contaminated with TCE and PCE can release vapors back into the soil which can enter nearby buildings and pose health risks to the people living and working in them. This is commonly referred to as vapor intrusion. The MPCA wants to take steps to reduce or eliminate vapor intrusion where possible.
Drinking water is not affected by the groundwater contamination at the site. Bloomington’s municipal water system currently meets all federal and state drinking water requirements.
In 2009, a property located within the Lyndale Avenue Corridor Site was referred to the MPCA when volatile organic compounds (VOCs) were found in the groundwater. The MPCA reviewed historic information on other contaminated properties within the Lyndale Avenue Corridor area in 2010 and found similar contaminants in the groundwater. Further investigation and sampling in 2012 and 2013 helped define the extent of PCE and TCE contamination in groundwater and also identified potential chemical vapor intrusion risks.
The MPCA collects vapor samples beneath the concrete floor on the lowest level of a building and has the samples analyzed to determine if there are chemical vapors present below the building. These samples are called sub-slab vapor samples. The analytical results are compared with vapor intrusion screening values (ISVs) established by the Minnesota Department of Health (MDH). If a chemical sub-slab vapor concentration is above a criterion of 33 times the ISV, there is the potential for chemical vapor intrusion and a vapor mitigation system is needed at the building. Residential buildings have a lower ISV criteria than commercial buildings.
Since 2014, sub-slab soil vapor samples have been collected from twenty-two single family homes, six apartment buildings, and twenty-two commercial properties. Thirteen single family homes, four apartment buildings, and fourteen commercial properties had sub-slab soil vapor concentrations at or above the screening criteria. The MPCA has installed vapor mitigation systems at twelve single family homes. Four commercial properties have had vapor mitigation systems installed. The owner of three apartment buildings and the owners of three additional commercial building owners have indicated that they are in the process of installing vapor mitigation systems.
Based on the results of recent sub-slab sampling, the area of vapor investigation has been expanded to the east and south.
When chemical vapors enter buildings through the foundation, the amount in indoor air is usually not high enough to affect most people’s health. The possible health effects from breathing TCE/PCE depends on the amount in indoor air and how long people breathe it.
The Minnesota Department of Health is most concerned about women in the first trimester of pregnancy because TCE exposures may increase the risk of heart defects to the baby.
Exposure to TCE for a long period of time may also affect the immune system. Long-term exposures to TCE/PCE may also increase the risk of certain types of cancer based on studies in workers or animals breathing very high levels of these contaminants (thousands of times greater than what may be found at the school).
For more information regarding health and vapor intrusion please go to the MDH website.
Minn. Department of Health