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To address Tetrachloroethylene (Perc) contamination identified in the area of a former dry cleaner (tenant spaces addressed as 2410-2412 10th Avenue) at the Sunrise Shopping Center facility, chemical treatment was conducted between May 2019 and January 2020, and a sub-slab depressurization system was installed/operated in the 2410 and 2412 tenant spaces beginning in 2020. No additional remedial actions are planned for this Site at this time.
Quarterly groundwater sampling for Perc was conducted on MW-5 on August 31st and November 11th, with results provided in the Quarterly Groundwater Sampling Reports dated September 29, 2021, and December 27, 2021. The quarterly sampling results continue to show Perc in MW-5 at concentrations above the Enforcement Standard. The most recent results from August and November 2021 show a slight increase in Perc concentration after near stable concentrations between September 2019 and May 2021. Quarterly sampling will continue until a Case Close Out Letter is issued for the Site.
Groundwater sampling was performed on all monitoring wells on August 5, 2021, as part of the assessment of potential groundwater impact for polyfluoroalkyl substances (PFAS). (PFAS sampling of MW-3 and MW-5 had been previously completed in March 2021 during the preliminary evaluation of emerging contaminants.) The August 2021 sampling was performed following the methodology proposed in the July 18, 2021, dated PFAS Additional Evaluation Work Plan. The results of the most recent PFAS sampling (and the March 2021 emerging contaminant sampling) were provided in the Emerging Contaminant Evaluation Report Amendment dated October 18, 2021. The report indicated that 1,4-Dioxane and n-Nonane were not identified in the groundwater at any location, but several PFAS constituents were observed in each of the monitoring wells. Many of the PFAS constituents observed were reported at concentrations below the recommended Preventative Action Limits (PALs), or are listed constituents with no recommended PAL. However, exceedances of the recommended PALs for one (1) or more PFAS constituents were observed in each monitoring well, and all monitoring wells except MW-201 indicated exceedances of the recommended Enforcement Standards for cumulative PFAS constituents. In a response email of December 9, 2021, WDNR indicated that further evaluation must be completed to determine the source of the PFAS impacts. Additional sampling for PFAS is planned for the first semi-annual 2022 time period.
The sump water treatment system within the Ace Hardware building has continued to operate successfully. Electronic reporting of the discharge sample results is completed monthly as required. The results of the monthly sump influent sampling continue to be stable but above the Enforcement Standards, while all contaminants in the treated effluent are reduced to levels well below the permitted discharge limits, and generally below the Limits of Detection. As directed by WDNR, the sump water and system discharge were also sampled for PFAS in August 2021. The results were provided in the October 18th Emerging Contaminant Evaluation Report Amendment. The results indicated comparable, but slightly lower PFAS concentrations in the sump water as compared to the MW-5 groundwater concentrations (consistent Perc results). All effluent concentrations were reported below the LODs. Therefore, results of the effluent sample indicate that the treatment system is effective in preventing any contaminants from discharging into the City of South Milwaukee stormwater sewer system and ultimately Lake Michigan.
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