St. Louis Park: Minnetonka Blvd. and Raleigh Ave. site

Request to add Minnetonka Boulevard & Raleigh Avenue South, St. Louis Park to Permanent List of Priorities: January 2020

MPCA staff recommend referring the Minnetonka Boulevard and Raleigh Avenue South site in St. Louis Park to the Minnesota Permanent List of Priorities (PLP). This will allow the MPCA State Superfund Program to use state funds to conduct investigation activities and response actions.

This site is located in an area with a mix of homes, apartments, government offices and commercial businesses.

Between 1981 and 1998, one building near this intersection was the location of several dry cleaning businesses. In 2001, that building was demolished and redeveloped as Fern Hill Place. The development included a level of underground parking, commercial space on the ground level, and three levels of condominiums.

What's the problem?

The Minnesota Pollution Control Agency (MPCA) conducted groundwater and soil vapor sampling at Fern Hill Place and several adjacent properties in June 2013. The investigation found elevated levels of tetrachloroethene (PCE) and trichloroethene (TCE). PCE is a chemical that was commonly used by dry cleaning businesses. TCE is a commonly used industrial solvent.

Concentrations of PCE and TCE were more than 10 times the value that the MPCA and the Minnesota Department of Health (MDH) considers safe for groundwater and soil vapor near residential properties.

Groundwater contaminated with PCE can release vapors that can migrate 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 take steps to reduce or eliminate it where possible.

Health concerns

The primary human health concerns associated with the Site are vapor intrusion risks resulting from PCE and TCE impacts in soil and groundwater. The risk of direct soil and/or groundwater exposure is unknown because the extent and magnitude of soil and groundwater contamination is unknown at this time.

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 this site).

For more information regarding health and vapor intrusion please go to the MDH website.

What's being done?

In 1998, Waldorf Nevins Cleaners ceased business operations, and the site was sold by the former owner of the property to be redeveloped as a mixed commercial and residential building (Fern Hill Place). The operator and former property owners enrolled in the Voluntary Investigation and Cleanup (VIC) program (ID# VP9360) in 1997 requesting MPCA assurances associated with the sale of the property to the Current Property Owner. During redevelopment activities in 2000, the Current Property Owner removed approximately 3,600 cubic yards of tetrachloroethylene (PCE) contaminated soil from the Site. PCE is commonly used as a dry cleaning solvent and is a hazardous substance under the definition in Minn. Stat. §115B.02, subd. 8.  However, significant contamination remained in place, and the full extent and magnitude of soil and groundwater impacts were not delineated. The residual contaminated soil and groundwater are continuing sources of chlorinated volatile organic compounds (VOCs) to soil gas, creating an ongoing risk for vapor intrusion.

In 2010, the MPCA’s Site Assessment (SA) Program (ID# SA4602) initiated further evaluation when PCE impacts were identified in groundwater and off-site soil gas. MPCA SA staff requested that the Former Property Owner, the Current Property Owner, and off-site commercial property owners conduct voluntary investigation and response activities; however, the MPCA’s requests were declined.

In 2013, the MPCA’s SA Program and conducted limited groundwater and soil vapor investigation and sampling at the Site and adjacent properties. In 2015 and 2016, the MPCA continued investigation activities including additional soil, groundwater, and soil gas sampling, installation and sampling of sub-slab vapor points, and evaluating surrounding buildings and utilities for potential vapor migration risk.

When redevelopment took place at Fern Hill Place, a vapor mitigation was installed. This has been a standard practice since to 2002 to control radon issues. This system needs to be tested to make sure it is working properly. At that time, the MPCA had difficulty gaining access to buildings in the area to conduct needed additional testing.

In November 2017, the agency tested soil vapors beneath the foundations of three of the Uptown West apartment buildings in the area. Concentrations of PCE and TCE vapors detected at the site were high enough to warrant installation of vapor intrusion mitigation systems to lower the vapor levels at four apartment buildings. The sampling identified elevated sub-slab vapor concentrations of PCE and trichloroethene (TCE) exceeding the MPCA’s Expedited Intrusion Screening Values (EISVs) beneath each of the three buildings.

At the request of the MPCA, in February 2018, the owner of the apartments, Uptown West Apartments (UWA), completed soil vapor mitigation of the buildings. Additional sampling conducted by the MPCA at the next three UWA buildings closest to the Site identified elevated soil vapor concentrations requiring mitigation of a fourth building and additional testing of another two buildings.

In September 2018, the MPCA requested that UWA inform the residents of the soil vapor concentrations, complete soil vapor mitigation of the fourth building, and conduct additional soil vapor testing at two others. 

Additional investigation is necessary to determine the extent and magnitude of the release and the source area.

Contacts

Greg Small
651-757-2304
gregory.small@state.mn.us

Minnesota Department of Health
651-201-4897
health.hazard@state.mn.us