| Comments: |
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, a Design Report Addendum/Remedial Action Plan (RAP) dated October 18, 2018, was submitted to WDNR proposing full-scale chemical injection activities. The RAP was approved by WDNR in a letter dated December 19, 2018. Subsequently, WDNR renewed the approval for coverage of the chemical injection of Potassium permanganate under WPDES permit WI-0046566-07 in a letter dated January 2, 2019.
Remedial actions included infiltration of Potassium permanganate from the surface combined with mechanical soil mixing. The mechanical mixing was performed by first removing the overlying concrete slab in both the 2410 and 2412 tenant spaces and then using a small excavator to dig up and âstirâ in the Potassium permanganate. The soil mixing was performed in the areas of highest observed PCE soil concentrations. Upon completion of the mechanical soil mixing and chemical treatment, the sub-slab depressurization system (SSD) was installed in both the 2410 and 2412 tenant spaces before replacing the concrete floor slab. With the chemical treatment completed and the SSD system installed, a remedial construction report describing the chemical treatment activities and providing the final âas-builtâ design of the SSD system will be prepared.
In addition to the remediation of the chlorinated contamination in the soil and groundwater, the sump water treatment system within the Ace Hardware building has continued to operate successfully throughout the first semi-annual 2020 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.
Two (2) quarterly groundwater sampling events were also conducted during the first semi-annual 2020 reporting period to assess the groundwater concentration of Perc in MW-5. The first quarter sampling was performed on January 17, 2020, with results provided in the Quarterly Groundwater Sampling Report dated March 4, 2020, and the second quarter groundwater sampling was performed on May 5, 2020, and the results were provided in the Quarterly Groundwater Sampling Report dated June 15, 2020. The quarterly sampling results continue to show that the Perc concentrations in the area of MW-5 remain above at levels above the Enforcement Standard (despite additional chemical injection in August 2019), with only a modest decline in groundwater concentration. However, Trichloroethene concentrations remain below the Preventative Action Limit. Quarterly sampling of MW-5 will continue, with the third quarterly sampling event to be completed in July 2020.
|
