The former Waldorf Cleaners dry cleaning business operated at 942 Lowry Ave NE, Minneapolis, from the 1940s to the 1980s. The business operated at this address as well as at the adjoining property across the alley to the west. The property to the west was a mechanical building that housed a steam boiler and was used to store chemicals, too.
The Minneapolis Community Development Agency began investigating the site in the early 2000s. Analysis of soil and groundwater samples found tetrachloroethylene (PCE) contamination. PCE, sometimes referred to as "perc," is a commonly used dry cleaning fluid.
What's the problem
In 2017, the site was investigated again by Hennepin County. Soil and groundwater samples once again showed PCE contamination, this time at levels prompting quick action.
When PCE gets into groundwater, it can move off the property or area where the contamination occurred. It can also release PCE vapors back into the soil which can migrate upward through the soil into nearby homes and buildings where it can pose health risks to the people living and working in them. This is commonly referred to as vapor intrusion. The MPCA wants to identify vapor intrusion and take steps to reduce or eliminate it where possible.
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 PCE depends on the amount in indoor air and how long people breathe it.
Long-term exposures to PCE may 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 vapor intrusion sites). At high levels in the workplace, PCE can also cause neurological effects such as vision changes or delayed reaction time.
For more information regarding health and vapor intrusion please go to the Minnesota Department of Health website.
What's being done
Hennepin County reviewed historical reports during the summer of 2017 in preparation for future transfer of the site to the city of Minneapolis for site redevelopment. In July 2017, the county hired an environmental contractor to assess soil vapor concentrations. When the site was first investigated back in the early 2000s, looking for elevated soil vapor levels was not a standard practice. During the investigation, elevated levels of PCE vapors were found near offsite residential homes at concentrations of 35,000 ug/m3 and 16,000 ug/m3.
Hennepin County contacted the MPCA Site Assessment Program in August 2017 because these detections which were above levels in a residential setting whereby the agency would take expedited action to investigate and correct the problem.
The MPCA hired a state contractor September 2017 to collect soil vapor samples from underneath the foundations of three properties closest to the site — 938, 946, and 952 Lowry Ave NE, Minneapolis. 938 Lowry Ave NE is a commercial property, 946 Lowry Ave NE is a commercial property currently owned and operated for residential housing, and 952 Lowry Ave NE is a residential property.
The results of these sub-slab samples indicated vapor mitigation systems are needed at all three properties. Vapor mitigation systems are designed and operate like a home radon mitigation system. The vapor mitigation system creates a slight depressurization beneath the building floor slab using a small fan installed in PVC piping. Vapors collected from beneath the building are then exhausted above the roof line.
A vapor mitigation system has been installed at 946 Lowry Ave NE, however the data from the post-verification sampling that was conducted after the system was put in has not been received yet. The owner of the commercial building at 938 Lowry Ave. has been informed of the need to install a vapor mitigation system, but they have not yet committed to doing so. The property owner at 952 Lowry Ave. has also been informed of the need to install a vapor mitigation system too, but the owner has signed a purchase agreement with the city of Minneapolis and will be moving out. The city intends to demolish the building so a mitigation system will not be installed at this location.
The Site Assessment Program plans to collect sub-slab samples at three additional properties beyond those sampled in September 2017. These properties are located at 954 Lowry Ave NE, and 2413 and 2501 Central Ave. Access letters have been sent to all three buildings and the MPCA has received signed access agreements for both properties on Central Ave. There has been no written response from 954 Lowry Ave NE.
Hennepin County is in close communications with the city and local neighborhood organizations for the ongoing area-wide redevelopment efforts in this community. The county is looking for assistance in formulating and disseminating an appropriate message to the neighborhood groups.
Minnesota Department of Health
Call — 651-201-4897
Email — firstname.lastname@example.org