Farmington: 3rd St. and Oak St. vapor intrusion site

A dry cleaning business once operated near the intersection of 3rd Street and Oak Street. The dry cleaning chemical perchloroethylene (PCE) contaminated groundwater under the property. Over time, the contaminated groundwater has migrated northeast towards the Vermillion River. There are 57 buildings in the area of concern.

The issue: Vapor intrusion

The groundwater contaminated with PCE could release PCE vapor that can rise through the soil and seep through basement and foundation cracks into homes and other buildings, where it could be inhaled by people. This is known as “vapor intrusion.” If vapor intrusion is occurring, it is likely that vapor levels are higher in basements than on upper floors.

If a problem is found at a property, the remedy for the situation is installing a vapor ventilation system, which operates like a radon mitigation system. If a building has a radon mitigation system that was installed by a certified contractor and is functioning properly, it is likely that the problem of PCE vapor in the building’s indoor air is being addressed.

The Minnesota Department of Health (MDH) is working closely with Minnesota Pollution Control Agency (MPCA) and U.S. Environmental Protection Agency (EPA) on this project because exposure to PCE vapor can be a health concern. MDH has a fact sheet about PCE and potential health impacts:

The next step is to test properties to determine if the the PCE present in the soil gas could make its way into homes, creating exposure for occupants. The EPA and the MPCA will need the cooperation of residents and property owners to compete this work.

The EPA will be doing the testing and mitigation work (to protect people's health) at affected properties, if needed. MPCA tested soil gas from borings in the public right of way to define an area of vapor concern. EPA will test the properties that may be affected in this area.

Map: Area of concern

This map shows the current area of concern for vapor intrusion along with results of soil gas testing. Click image for larger view.

Farmington area of concern



Time period Activity
February 19 Open house for residents and property owners with staff from EPA
to answer your questions and sign access agreements.
Where: Farmington City Hall, 430 3rd Street, Farmington, MN 55024
When: Feb 19 from noon to 8 pm
March 2015

EPA meeting with residents and testing of homes

June 2015

Indoor air sampling in home that exceeded sub slab screening levels


For questions about this vapor intrusion site, contact Sonia Vega, U. S. EPA at 630-481-5025 or at

For information about health issues related to this site, contact the Minnesota Department of Health, Emily Hanson, 651-201-4602 or

Minnesota Pollution Control Agency (MPCA) site remediation contacts
Edward Olson 651-757-2627 or
Dave Scheer 651-757-2693

Additional information and documents

The ground water contamination affected two private wells which were found to have contamination levels above the Health Risk Limit for PCE.  These residences were immediately provided with whole-house filtration systems. The municipal water system is safe and is not at risk. Groundwater monitoring has continued at several private wells and monitoring wells.  No private drinking water wells exceed standards.

An air exchange system was installed in the building where the original dry cleaning business existed. Indoor air samples in this building have met air standards, and there are no health concerns here.

The size of the area of vapor concern is largely a result of the health standards being tightened in September 2014. Soil gas investigation along right-of-way access during the spring of 2014 detected PCE, but not at levels of concern to residential areas. Re-evaluating that testing  data in the context of the new lower standard, along with new soil gas data collected in the winter 2014 has resulted in a larger area of vapor concern.