OTTER TAIL COUNTY
Congressional District # 07
PERHAM ARSENIC SITEEPA ID# MND980609572
Last Updated: November, 2011
Site DescriptionThe Perham Arsenic site consists of a six- to eight-foot deep pit and associated groundwater plume that emanated from the pit area, which is located in the southwest corner of the Otter Tail County Fairgrounds in Perham, Minnesota. From the 1930s until 1947, the site was used to mix United States Department of Agriculture supplied arsenic with sawdust and molasses, which was used as a pesticide to control an outbreak of grasshoppers that had threatened crops throughout the Midwest. In 1947, approximately 200 to 2,500 lbs. of arsenic pesticide was buried in a shallow pit. In 1971, Hammers Construction Company purchased the property, adjacent to the southwest corner of the fairgrounds, to build offices and a warehouse. In 1972, the company installed a groundwater well to provide water to the facility. Eleven employees were poisoned by arsenic-contaminated groundwater. The well was capped, and the city of Perham extended its municipal water supply to the facility. Approximately 2,000 people live in the city of Perham and drink groundwater from the sand and gravel aquifer below.
This site is being addressed through federal and state actions.
Threats and ContaminantsGroundwater and soil onsite are contaminated with arsenic. Potential health threats include ingesting or coming in direct contact with contaminated groundwater or soil.
Cleanup ProgressIn 1982, a clay cap was installed to reduce leaching of arsenic from the pit. In 1984, the Minnesota Pollution Control Agency (MPCA) excavated 200 cubic yards of arsenic wastes and contaminated soils from the pit, backfilled the pit, and reestablished the clay cap. Groundwater wells were installed to monitor the groundwater plume. At that time, the arsenic plume was expected to dissipate. Continuing groundwater monitoring indicated that arsenic levels in groundwater were not dissipating as expected. In 1992 and 1993, the United States Environmental Protection Agency (U.S. EPA) conducted a remedial investigation and feasibility study (RI/FS) which concluded that groundwater was still contaminated with high levels of arsenic [1,260 parts per billion (ppb); the Safe Drinking Water Act/maximum contaminant level (MCL) for arsenic was 50 ppb at the time and is now 10 ppb], and the contamination had been migrating in the groundwater east toward an adjacent farm field. No remaining arsenic contamination was found in the pit or under the Hammers Construction Company building. A record of decision (ROD) was issued on March 31, 1994, which selected a groundwater pump and treat remedy along with interim deed restrictions to restrict groundwater use. The ROD also required that U.S. EPA connect a nearby resident to the city of Perham municipal drinking water supply.
In September 1994, U.S. EPA began the design of the pump and treat remedy. In December 1994, U.S. EPA connected the nearby resident to the city of Perham municipal drinking water supply. During the design, U.S. EPA received a comment suggesting that an existing building be retrofitted to house the treatment unit instead of building a new treatment building. As a result, the design was revised for an estimated $500,000 cost savings. The design was completed in 1997. U.S. EPA began construction in August 1997. RA construction was completed on September 29, 1998. MPCA took over operation of the system in July 1999. The second five-year review at this site was completed in 2006 and concluded that the cleanup continues to be protective of human health and the environment, with additional Institutional Control (IC) issues needed to be adressed. The 10 year LTRA (Long-Term Response Action) period for the Minnesota state lead Site was completed at the end of 2009, and documented in a notification memo between USEPA and MPCA in 2010. A third five year review was completed and signed for the Site in July 2011.
ContactsRemedial Project Manager, U.S. EPA
jeffrey gore (firstname.lastname@example.org)
Community Involvement Coordinator, U.S. EPA