Special Well and Boring Construction Area
Le Hillier is a small community in Blue Earth County near the confluence of the Blue Earth and Minnesota Rivers. At the time of the advisory, there were no central water-supply or sewage systems serving the city. Most of the 200 homes in the area were supplied by individual drive-point wells driven to approximately 30 feet in depth. A few homes had wells cased to the St. Lawrence confining layer with open-hole construction into the Franconia or Ironton aquifer. Many of the individual sewage disposal systems consisted of perforated 55-gallon steel barrels.
In 1981, following a tip on the Minnesota Pollution Control Agency (MPCA) "hotline" about dumping of hazardous wastes, groundwater contamination was verified. Major contaminants detected in the drift and alluvium and some bedrock wells were nitrates and volatile organic chemicals (VOCs), primarily trichloroethylene.
In September of 1981, an advisory was mailed to licensed well contractors working in the Mankato area. The advisory area is in parts of Sections 14 and 23, Township 108 North, Range 27 West, Blue Earth County, bounded by East Hawley on the west and the Blue Earth River on the east, north and south. The contractors were specifically told that residents with elevated levels of trichloroethylene had been advised to use alternate drinking water sources, and that the Health Department was not advising that contaminated wells be deepened or that new deeper wells be constructed until the source, extent, nature and hydraulics of the contamination was known.
The Minnesota Pollution Control Agency initiated several superfund studies for identifying the source of the contamination and furnishing the residents of the area a safe water supply. Le Hillier received a grant and constructed a rural water-supply system. Mankato required assurances that the contamination would be cleaned up and that the discharge of sewage into the ground upgradient from their Ranney well would be discontinued. A central sewage collection and treatment facility has been proposed but not constructed. A program was implemented to seal multi-aquifer wells to prevent contamination of the Franconia-Ironton-Galesville aquifer.
A remedial study has been completed and a proposal to use U.S. Corp of Engineers dike flood control wells plus other wells to pump contaminated water. The water is being air stripped of VOCs and discharged to surface water.
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Contact the MDH Well Management Section
651-201-4600 or 800-383-9808
Minnesota Department of Health