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Baytown Township Groundwater Contamination Site

This page provides information about cleanup of the Baytown Township Groundwater Contamination Site (Site). More detailed information about this Site can be found in technical reports primarily available from the Minnesota Pollution Control Agency (MPCA). Some Site reports are also available from the Minnesota Department of Health (MDH).

Where is the site?

The Site is located in central Washington County, Minnesota. The Site is defined essentially by the MDH’s Special Well and Boring Construction Area (SWBCA). The SWBCA was enacted to regulate the construction of new wells. At their widest extent, the SWBCA and the Site are approximately bounded on the north by 50th Street and on the south by 20th Street. The contamination extends from the eastern portion of the city of Lake Elmo through Baytown Township, West Lakeland Township, and the city of Bayport to the St. Croix River as shown in the map below.

Map of site

Map of Baytown Township Groundwater Contamination Site

What and where is the contamination?

The main contaminant of concern that has been released to groundwater at the Site is 1,1,2-trichloroethene (TCE). The TCE plume is located within the Site and is approximately five miles long and covers about seven square miles. The TCE plume affects four major groundwater aquifers. The TCE plume for the unconsolidated and Prairie du Chien aquifers is shown above. The TCE plume for the Jordan Aquifer can be viewed in the Jordan plume map.

The TCE plume for the deepest aquifer, the Tunnel City Aquifer, can be viewed in the Tunnel City plume map. Approximately 400 homes and several businesses located within the TCE plume are served by private wells.

New Health Based Value for TCE and drinking water

The Minnesota Department of Health (MDH) recently concluded a review of the potential health effects associated with TCE exposure from drinking water and released a new Health Based Value (HBV) of 0.4 micrograms per liter (µg/L) on May 21, 2013. The MDH recommends using the HBV instead of the existing Health Risk Limit (HRL) of 5.0 µg/L, and the MPCA has adopted 0.4 µg/L as the new drinking water limit for TCE in domestic water supply wells. This change will result in additional MPCA actions over the coming months. Here’s the MPCA’s plan for addressing the HBV:

Domestic water supply wells

The MPCA has response action responsibilities for wells on properties platted and approved before April 9, 2002, in Baytown and West Lakeland Townships and in the city of Bayport.

  • Wells with TCE concentrations greater than or equal to 5.0 µg/L already have response actions, primarily granular activated carbon (GAC) filters, in place. Additional response actions are not needed for these wells.
  • Wells that do not have GAC filters and have two consecutive TCE concentrations greater than the HBV of 0.4 µg/L (with at least one sample more recent than June 1, 2012) will be offered new, MPCA-supplied GAC filters without the need for additional sampling. If GAC filters were already installed by the property owner, the MPCA will offer to provide future maintenance for the filters. If the most recent sample data are older than June 1, 2012, the well will be sampled to obtain current data. If the new sample results in two consecutive TCE detections above 0.4 µg/L, new, MPCA-supplied GAC filters will be offered. As of April 2014, the MPCA had installed nearly all of these additional GAC filters.
  • Wells with TCE concentrations of 0.30 to 0.40 µg/L will have their sampling frequency increased from once every four years to three times per year.
  • Wells with TCE concentrations of 0.20 to 0.29 µg/L will have their sampling frequency increased from once every four years to twice per year.
  • Wells with TCE concentrations of 0.10 to 0.19 µg/L will be sampled once every year.

Property owners in Baytown and West Lakeland Townships have response action responsibilities for wells on properties platted and approved after April 9, 2002. These wells are addressed by township ordinance. The township ordinances require the installation and maintenance of a GAC filter if the TCE concentration reaches 0.5 µg/L or more. At this time, the MPCA does not anticipate installing GAC filters on existing wells installed after April 9, 2002. When new wells are approved, GAC filters will be installed and maintained by the property owner.

HTML Content Baytown Township Groundwater Contamination Site (Minn. Dept. of Health) External Link

What does the remedy include?

The MPCA selected a remedial action, or cleanup, for releases at the Site that will protect the public health and welfare and the environment. The remedial action was set forth in the July 2007 Record of Decision (ROD) Amendment. The major operable unit components of the selected remedy include:

  • Operable Unit 1 (OU1) — Continued monitoring of private wells, sampling of private water supply wells, and installation, change out, and maintenance of granular activated carbon (GAC) filter systems as previously designated in the original May 2000 ROD.
  • Operable Unit 2 (OU2) — An air stripping treatment system at Bayport Municipal Well #2. The city of Bayport is responsible for ongoing operation and maintenance of this air stripper.
  • Operable Unit 3 (OU3) — Containment of TCE in groundwater at the primary source zone — a former metal fabricating shop located at 11325 Stillwater Boulevard in Lake Elmo.

In early March 2008, the MPCA completed construction on a hydraulic barrier to contain the TCE plume and prevent off-property migration of contaminated groundwater. The barrier consists of four extraction wells spaced so their influence overlaps and collectively captures the contamination before it can migrate off the property. The extracted water is then treated by air stripping to remove the TCE from the water.

The pumps for the barrier system were started up on March 17, 2008. This barrier is operating continuously at approximately 70 gallons per minute with the exception of down time for maintenance or tests. Its purpose is to control the groundwater gradient so that high concentrations of contamination are unable to continue to migrate to the east. The barrier likely will operate for more than 10 years.

The four extraction wells recover the groundwater and pump it to a low-profile air stripper located within a treatment building. The air stripper removes more than 99 percent of the TCE from groundwater, attaining concentrations under 0.4 µg/L below the MDH HBV. The water is then discharged back to the soil using horizontal wells approximately 25 feet underground. The extraction wells have been successful at reducing downgradient TCE concentrations in Lake Elmo groundwater by more than 70 percent.

Potential vapor intrusion risk

In November 2008, the MPCA conducted an initial screening for potential TCE vapor intrusion related to the Baytown Site. The following document provides an update:

Granular activated carbon filters

The MPCA has installed whole-house GAC filters in a number of residences near the Baytown site to ensure safe drinking water. This fact sheet gives general information on their use and maintenance.

Where can I get more information?

All documents prepared during the investigation, selection, design and construction of the remedy are available for review at the MPCA, 520 Lafayette Road N., St. Paul, Minn.

Testing your groundwater

Information about testing your groundwater is available on the Minnesota Department of Health's Web site:
HTML Content Well Management Program (Minn. Dept. of Health) External Link

Staff contacts

Links to related information

Last modified on April 10, 2014 14:42