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Construction crews worked 12-hour days five days of the week (and some work on Saturdays) over the last month to finish excavating polluted soils from a contaminated site underneath Highway 61 in downtown Grand Marais. The hole is now filled back in, but for a time the dig was two feet before the water level before they hit non-contaminated earth. Staff photos/Brian Larsen
The big hole that was excavated near the Voyager Brewery and Dairy Queen on Highway 61 is filled in and the polluted soil has been removed.
The Minnesota Pollution Control Agency (MPCA) requested that a portion of Highway 61 be dug up to remove pollution left from a long-closed gas station.
According to MPCA Project Manager Katherine Lewison, approximately 2700 cubic yards of petroleum contaminated soils were anticipated to be removed during the excavation. However, she noted, “We don’t have the final quantity of soils that were removed yet, but I will forward on this information as soon as we have it. It is expected to be a bit less than the original estimated 2700 cubic yards.”
The petroleum contaminated soils were hauled to an MPCA permitted composting facility located in Schroeder, where microorganisms break down the petroleum contamination.
Lewison said the entire project will cost approximately $1.07 million.
The contamination was discovered in 1996; a petroleum release was reported to the MPCA from petroleum underground storage tanks associated with the former Cobblestone Service Station (CS Service). Contamination was found during a site assessment that was conducted prior to tank removals. Since that time, the MPCA has been investigating the site (which included installing numerous soil borings and monitoring wells) to define the extent of the contamination, monitor the plume, and determine risks to nearby properties water supply wells, surface water and underground utilities. Lewison said due to the high levels of contamination that were discovered, it was necessary to measure groundwater contaminant concentrations in monitoring wells over time to establish plume stability and determine risk.
It was determined that the remaining petroleum contaminated soils would continue to pose a risk if left on site. The excavation of petroleum-contaminated soils was needed to prevent petroleum contamination from entering Lake Superior above acceptable levels (surface water standards set forth in Minnesota Administrative Rules Chapter 7052), and to mitigate the potential risk of petroleum vapors intruding into nearby buildings, said Lewison.
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