Region 5 Superfund (SF)

U.S. EPA REGION 5
BLUE EARTH COUNTY
LEHILLIER

Congressional District # 01

LEHILLIER/MANKATO

EPA ID# MND980792469
Last Updated: April, 2008

Site Description

The Lehillier/Mankato site, located in Blue Earth County, Minnesota, is a 1,000-acre site where uncontrolled dumping occurred until 1972.  In the early 1980s, the Minnesota Pollution Control Agency (MPCA) confirmed volatile organic compound (VOC) contamination of groundwater in the area by sampling domestic wells.  A number of small dumps were known to exist in the area, but a specific source of the contamination was not found.  Several residential wells were impacted, and one of the municipal wells for Mankato, a city of 30,000 people, is directly downgradient and less than one-quarter mile from the VOC plume.  The surficial aquifer, which is the impacted aquifer at the site, is the drinking water source for Mankato.  No contamination has been detected to date in the municipal well near the site. A new municipal well is currently under construction approximately one-quarter mile to the north of the contamination. Both municipal wells draw from the shallow aquifer.

Site Responsibility

The site is being addressed through federal and state actions.

Threats and Contaminants

Prior to site cleanup actions, the groundwater was contaminated with VOCs.  Residual groundwater VOC contamination remains at the site.  Drinking or coming into contact with VOC-contaminated groundwater may pose a health risk.  Currently there are no known users of the groundwater as a drinking water source.  To achieve an acceptable level of risk, the cleanup level for the main VOC contaminant, trichloroethylene (TCE), was set at 2.8 micrograms per liter.

Cleanup Progress

In 1983, Lehillier residents were provided with bottled water.  In 1985, a municipal water supply system was constructed for the residents of Lehillier through a Housing and Urban Development grant.  In 1985 a Remedial Investigation (study of the nature and extent of site contamination) and a Feasibility Study (a study of the site cleanup alternatives) were conducted.  Design of a groundwater cleanup system was completed in 1988.  The groundwater treatment system was constructed in 1989 by MPCA under a Cooperative Agreement with U.S.EPA.  The groundwater treatment system consisted of extracting contaminated groundwater, treating it with an air stripper and discharging it to the Minnesota River.

The groundwater extraction and treatment system operated until December 1997, at which time the seven extraction wells were shut down to evaluate progress toward the cleanup goal of 2.8 micrograms per liter of TCE in groundwater.  At that time, the cleanup goal for TCE had been achieved in most of the monitoring wells.

In 2003, the Lehillier/Mankato site was deleted from the Minnesota Permanent List of Priorities (PLP).  A third five-year review of the remedy, completed in September 2006, found the remedy to be protective of human health and the environment.  There is no known use of groundwater in the area for drinking, and the extent of TCE-contaminated groundwater is limited to an area one-quarter mile away from the municipal wells. Because of the low levels of TCE remaining in groundwater and the limited area of contamination, in 2007 the air stripper was dismantled and five of the six extraction wells were removed. Minnesota Pollution Control Agency (MPCA) has agreed to undertake a remedial action if it is required in the future. An ordinance restricting groundwater use in the area of the plume is currently under review by South Bend Township.

Contacts

Remedial Project Manager, U.S. EPA
mary tierney (tierney.mary@epa.gov)
(312) 886-4785

Community Involvement Coordinator, U.S. EPA
Don De Blasio
(312) 886-9749

Aliases

LEHILLIER MANKATO SITE
LEHILLIER/MANKATO GROUNDWATER
LEHILLIER/MANKATO SITE

 

Site Profile Information

This profile provides you with information on EPA's cleanup progress at this Superfund site.