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To address both soil and groundwater 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 of the underlying soils was conducted between May 2019 and January 2020. Subsequently, a sub-slab depressurization (SSD) system was installed in the 2410 and 2412 tenant spaces during the first semi-annual period of 2020. The SSD system startup was initiated on August 10, 2020, and the first verification vacuum testing was performed on August 24, 2020. Results of the chemical treatment and startup performance testing of the SSD system were documented in a Remedial Construction Report dated September 8, 2020.
In a letter dated November 23, 2020, WDNR required that another round of sub-slab vapor sampling and confirmation vacuum testing be completed. The additional sampling and verification testing was performed in December 2020 and February 2021. The result of the additional sampling/testing were submitted to WDNR in a Remedial Construction Report Addendum dated April 1, 2021. No additional remedial actions are planned for this Site at this time.
In addition to requiring vapor sampling and performance testing, WDNR requested that groundwater sampling be performed as part of a preliminary evaluation for potential contamination associated with emerging contaminants, specifically 1,4-Dioxane, n-Nonane, and polyfluoroalkyl substances (PFAS). The sampling was performed on March 11, 2021, consistent with activities proposed in the January 25, 2021, dated Emerging Contaminant Evaluation Work Plan. The results of the sampling for emerging contaminants were provided in the Emerging Contaminant Evaluation Report dated April 15, 2021. The report indicated that 1,4-Dioxane and n-Nonane were not identified in the groundwater at MW-5, but several other PFAS constituents were observed. In a response letter dated May 19, 2021, WDNR indicated that further evaluation of the potential for PFAS impacts should be performed. Submission of a work plan and subsequent performing of the additional sampling for PFAS are planned for the second semi-annual 2021 time period.
Two (2) quarterly groundwater sampling events were conducted during the first semi-annual 2021 reporting period to assess the groundwater concentration of Perc in MW-5. The first quarter sampling was performed on January 18, 2021, with results provided in the Quarterly Groundwater Sampling Report dated March 3, 2021, and the second quarter groundwater sampling was performed on May 3, 2021, and the results were provided in the Quarterly Groundwater Sampling Report dated June 30, 2021. Quarterly sampling will continue until a Case Close Out Letter is issued for the Site.
The quarterly sampling results continue to show that the Perc concentrations in the area of MW-5 remain at concentrations above the Enforcement Standard. The most recent results of groundwater sampling from September 2019 through the most recent sampling of May 2021 indicate relatively stable Perc concentrations in MW-5. All Trichloroethene concentrations have remained below the Preventative Action Limit since July 2019.
The sump water treatment system within the Ace Hardware building has continued to operate successfully throughout the first semi-annual 2021 period. Required monthly discharge samples demonstrate that all contaminants the sump water (including Perc), are reduced in concentration to levels well below the permitted discharge limits, and generally below the method detection limits. Electronic reporting of the discharge sample results is completed monthly, as required under WPDES permit WI-0046566-07. As directed by WDNR in the May 19, 2021, response letter, the sump water and system discharge will be sampled for PFAS during the second semi-annual 2021 time period.
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