Frequently asked questions

About the Highway 100 and County Road 3 groundwater plume site

What is the difference between the Reilly Tar & Chemical Site in St. Louis Park and the Highway 100 and County Road 3 groundwater plume site?

These are two different chemical releases that were caused by different sources. The Reilly Tar & Chemical Corp. contamination is mainly creosote, which contains polycyclic aromatic hydrocarbons (PAHs) that were once used in wood treating operations. The Reilly Site was listed on the federal National Priorities List. Since the late 1970s, U.S. EPA and MPCA, in partnership with the city of St. Louis Park, has overseen the cleanup.

Contamination at the Reilly Site is the result of:

  • Wastes discharged directly to a ditch which flowed into a wetland on the southern side of the property
  • Contaminated soil from leaky pipes and various processes that spilled during operations
  • Creosote and waste materials that likely seeped down into several wells that had been used for irrigation when the property was a beet farm

See the EPA’s Reilly Tar webpage for more information.

The Highway 100 and County Road 3 groundwater plume site contamination consists of volatile organic compounds as detailed above. MPCA staff conducted investigations to identify the source of the release, but additional work is needed to complete the investigation.

Is my drinking water safe? 

Yes. The cities of Edina and St. Louis Park both have drinking water treatment systems that meet federal Safe Drinking Water Act requirements and Minnesota's health risk standards. The systems for both cities treat for VOC contamination associated with the Highway 100 and County Road 3 site. The MPCA worked with both cities to design treatment plants that meet the state and federal standards and eliminate VOCs.

What are the possible health effects of VOCs?

VOCs are typically described as human carcinogens and can also cause problems with liver and kidney function. The potential for VOCs to be a health concern depends on the toxicity and concentration of the contaminant, the exposure conditions, and the duration or exposure. Factors like age, health condition, gender, and exposure to other chemicals can impact potential health effects for individuals.

What effect does the Highway 100 and County Road 3 Groundwater plume site have on property values? 

The EPA cannot predict how contaminated groundwater will affect individual property values. A good resource for property value information is a local government agency, such as your local planning commission, or a local real estate professional. They are more experienced in appraising property values and determining the effect of contamination on property values. The deep groundwater plume does not affect individual properties as it is 300 feet deep.

Is the soil in my yard contaminated?

The proposed NPL listing is for the deep groundwater plume, which is at a depth of more than 300 feet. The contamination does not affect the soil on individual properties.

Why is the site being listed as the large, deep plume and not a source area or smaller, shallow plume?

If EPA can attribute contamination to specific sources, sites can be listed on the NPL as a source rather than a groundwater plume with an undetermined source. Since the source of the Highway 100 and County Road 3 groundwater plume site is still in question, the site is evaluated as a groundwater plume with an undetermined source. 

When the investigation is complete, the source areas will be better defined. Also, the impacts to the municipal wells from the large, deep plume elevates the site’s Hazard Ranking System score. This is necessary to meet the NPL proposal.

How was the size of the deep plume determined?

The MPCA determined the extent and magnitude of the plume in the drinking water aquifer using existing wells that are open to aquifer, including:

  • Monitoring wells installed as part of the Reilly site investigation
  • Industrial production wells
  • Golf course irrigation wells
  • Municipal wells 

The plume is defined by wells where chlorinated VOC contamination was detected above the MDH’s health-based standards.

Have other NPL Superfund sites with groundwater plumes provided a model for this listing?

Yes. Many of the more than 1,300 sites on the NPL include a groundwater contamination plume. Two examples in Minnesota are the New Brighton/Arden Hills Superfund Site (also known as the Twin Cities Army Ammunition Plant or TCAAP Site) and the Baytown groundwater contamination site. The TCAAP Site plume extends under several cities including New Brighton, Arden Hills, Columbia Heights, St. Anthony, and Minneapolis. The Baytown site is approximately five miles long, covers about seven square miles, and extends from the eastern portion of Lake Elmo through Baytown Township, West Lakeland Township, and Bayport to the St. Croix River.