Minnesota Pollution Control Agency

Contact: CoriAhna Rude-Young, (651) 296-5965 St. Paul, Minn. -- Since March, the Minnesota Pollution Control Agency (MPCA) has been using an innovative hydraulic barrier to contain a plume of ground water contaminated with trichloroethene (TCE) at the Baytown Superfund site in Lake Elmo. The barrier includes ground-breaking technology for discharging the clean, treated water underground through horizontal boreholes. The hydraulic barrier consists of four extraction wells spaced so they collectively capture the contamination from the plume before it can migrate off the property. The extracted water is treated through a process called "air stripping," which removes more than 99 percent of the TCE. The treated water contains less than one part per billion of TCE, which is below the Minnesota Department of Health's Health Risk Limit of five parts per billion. After it is treated, the water is discharged back to the soil about 25 feet underground through horizontal boreholes. Much of it returns to the water table where it can be used in the future. Terracon Consultants of White Bear Lake designed the horizontal borehole system for the MPCA. It is thought to be the only system of its kind in the Midwest. The purpose of the system is to keep ground water with high concentrations of TCE from moving beyond the barrier to the east. The pumps for the barrier system, which were started on March 17, 2008, extract water continuously at a rate of 70 to 100 gallons per minute. The barrier will likely operate for at least five years. Eventually, TCE concentrations are expected to decline enough so residents will no longer need filters for their well water. The Baytown site, located in central Washington County, extends from the eastern portion of Lake Elmo through Baytown Township, West Lakeland Township and the city of Bayport to the St. Croix River. The TCE plume is approximately five miles long and covers about seven square miles. Private wells serving approximately 650 homes are located within the plume. More than 170 of these homes served by these private wells have filters to treat their water. Another 3,200 persons in Bayport are served by municipal wells that are within the plume.