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A former gray iron foundry, located in the Village of Sparta, Michigan, had been in operation since the 1920s, where solvents and lubricating oils were used in the production of piston rings and other products. Gasoline, diesel fuel, and mineral seal oil were also stored at the site in underground tanks. Slag, foundry sand and grinding wastes had been disposed of on site. Previous investigations identified elevated concentrations of trichloroethylene (TCE) and tetrachloroethylene (PCE) in soil and groundwater samples exceeding the Michigan Department of Environmental Quality (MDEQ) criteria. This posed a potential vapor intrusion (VI) risk to nearby residences.
This area had undergone many previous investigations and remediation activities were completed by the MDEQ. Approximately 14,000 tons of contaminated soils were removed in 2012 and groundwater monitoring wells were installed. Monitoring wells and soil gas sampling results in 2015 verified VI was not a concern to the north or west of the source area. However, there was a potential VI risk in the residential area to the east and south.
Therefore, AKT Peerless was contracted to conduct remedial investigation activities to identify whether or not a VI risk was present in the residential area. If VI concerns were identified, vapor mitigation systems were to be designed and installed.
AKT Peerless conducted remedial investigation activities to better define the horizontal and vertical extent of the known soil gas and groundwater contamination identified during previous subsurface investigations in the residential area near the foundry. These activities included groundwater plume delineation, soil gas sampling, sub-slab soil gas assessments and indoor air sampling at select residences to determine the potential risk from harmful vapors entering the residences. The results of the investigation would assist in designing and implementing remedial options, which would include vapor mitigation systems.
Soil gas results revealed a potential risk from harmful vapors entering two residences. AKT Peerless designed and installed two active sub-slab depressurization systems and sealed sumps in these residences. AKT Peerless also conducted performance monitoring of the systems to demonstrate effectiveness of the remedies, reported monitoring results to the MDEQ and provided operations and maintenance documentation to the MDEQ and affected homeowners.