The Minnesota Pollution Control Agency (MPCA) will test petroleum cleanup technologies at the former Town & Country Oil site in Mora in an effort to continue preventing contaminants from migrating to nearby city water wells. Gasoline and diesel fuel leaked into the ground at the site, located at the southwest corner of Maple Avenue and Highway 65, some 15 years ago.
Mora city officials expressed concern that a private well owned by Jerry’s Bait Shop and located adjacent to the leak site, is actually causing the underground contamination to move southwesterly in the direction of the city’s Well No. 5, located next to a city water tower just south of Mora High School and east of the Kanabec County Courthouse.
The bait shop well, located behind the building, produces about 45,000 gallons of raw untreated water that is circulated in minnow tanks. The bait shop also is connected to city water but the chlorine is harmful to minnows and can’t be used unless the chlorine is removed. Shop owner Don Larson previously expressed concern that sealing the bait shop well would force him to purchase water from the city, install a pre-treatment system to remove the chlorine, and increase his costs.
Petroleum Remediation Project Leader Laurie Kania pointed out that the MPCA, with the assistance of contractor West Central Environmental Consultants (WCEC), continues to monitor groundwater at the site in Mora (identified as Leak No. 3807) and will be testing several different remediation technologies to clean up the source of the contamination.
“The pilot testing of these remediation technologies to determine their effectiveness at this site will begin spring of 2016,” Kania noted. “We are also working with the owners of Jerry’s Bait Shop to obtain their permission to install a water treatment system to treat city water and seal their supply well.”
Mark Smith, the site hydrogeologist, said the technologies include air sparge/soil vapor extraction (AS/SVE) and Multi-Phase Extraction (MPE), which involved installing additional wells to be used for pilot testing.
Soil Vapor Extraction applies a vacuum to unsaturated zone soil to induce the controlled flow of air and remove volatile and some semi-volatile organic contaminants from the soil.
Air Sparging involves the injection of air through a contaminated aquifer to remove volatile and semivolatile organic contaminants by volatilization. The injected air helps to flush the contaminants into the unsaturated zone for treatment.
Multi-Phase Extraction uses a vacuum system, sometimes combined with a downhole pump, to remove various combinations of contaminated groundwater, separate-phase petroleum product and vapors from the subsurface. The system lowers the water table around the well, exposing more of the formation for vapor extraction.
More details about the petroleum remediation technologies can be found as the U.S. Environmental Protection Agency’s website: http://www.epa.gov/remedytech/remediation-technology-descriptions-cleaning-contaminated-sites.
Henry Fischer is a contributing local government writer for the Kanabec County Times and Pine City Pioneer