Long Prairie Ground Water Contamination

Overview

The Long Prairie Ground Water Contamination site sits in Long Prairie, Minnesota, and has been on the National Priorities List since June 1986. The site includes a 7,000-square-foot source area and a half-mile-long groundwater plume. About 350 homes with private wells were affected before public water supply extensions and service connections were put in place to address drinking water exposure.

Seven contaminants of concern have been identified in the soil and groundwater. They include tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene, trans-1,2-dichloroethene, vinyl chloride (VC), and 1,1,1-trichloroethane. These are volatile organic compounds, or VOCs, chemicals that can vaporize easily and pose health risks when people are exposed to them through drinking water or soil contact.

Cleanup has moved through several phases. A soil vapor extraction (SVE) system ran for four years and met its cleanup goals, finishing in December 2001. A groundwater pump-and-treat system uses granular-activated carbon and an air stripper to pull contaminated water out of the ground and clean it. In 2007, mineral oil was injected into the groundwater to speed up the natural breakdown of contaminants. The groundwater system is expected to keep running for roughly 15 more years. Recent monitoring data show the plume is shrinking. The Minnesota Pollution Control Agency (MPCA) and the U.S. EPA oversee the work. A newer SVE investigation under Operable Unit 02 began in September 2021, with a feasibility study and cleanup decision expected between 2027 and 2028.

EPA's most recent five-year review, completed in September 2022, confirmed that the current remedies protect public health and the environment in the short term. Exposure pathways that could cause unacceptable risks are under control. Most residents are connected to the public water system, and health advisories cover the area where groundwater still exceeds cleanup goals. Groundwater migration is stabilized and is expected to stay within the original contamination area. Not all cleanup goals have been met across the entire site yet. The site remains on the National Priorities List and is not yet ready for anticipated reuse. Institutional controls, including zoning restrictions, are in place to prevent residential uses and other activities that would be inconsistent with current cleanup levels. One business currently operates on-site.

Community members with questions can contact the EPA's Community Involvement Coordinator or Remedial Project Manager. The next five-year review is estimated for late 2027.