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Following WDNRâs approval letters dated June 27th and July 7, 2018, a pilot-test chemical injection was performed on July 19-20, 2018. The pilot scale data was used for the design of a full-scale in-situ chemical injection system to address both soil and groundwater chlorinated solvent contamination in the area of a former dry cleaners (i.e., the tenant spaces addressed as 2410-2412 10th Avenue). The pilot testing included the subsurface injection of two (2) chemical oxidants around the 2410-2412 tenant spaces. The July 30, 2018, groundwater sampling of MW-5 (located behind the 2410 tenant space), served as both the third quarter monitoring event and as a post-injection confirmation sampling event. Post-injection confirmatory soil sampling was performed August 2, 2018.
A discharge monitoring report was submitted on August 13, 2018, as required under WPDES permit WI-0046566-07. The NR 140 Exemption Post-Injection Report, dated September 18, 2018, included a summary of the pilot-scale injection information collected during injection activities.
The post-injection/third quarter groundwater sampling results were provided in the Quarterly Groundwater Sampling Report dated August 17, 2018. After a meeting with WDNR on September 14, 2018, a Design Report Addendum/Remedial Action Plan (RAP) dated October 18, 2018, was submitted to WDNR. The RAP documented the pilot-scale injection activities and the post-injection confirmation sampling results. The third quarter groundwater concentration of Tetrachloroethene (Perc) in MW-5 showed a decrease, but remained above the Enforcement Standard, and the fourth quarter groundwater sampling performed on October 11, 2018, showed a rebound in Perc concentrations (as documented in the Quarterly Groundwater Sampling Report dated October 29, 2018). Therefore, further chemical injection was proposed in the October 2018 RAP.
As noted in the RAP, direct injection of a chemical oxidant into the subsurface under pressure was determined to be a feasible remedial method at depths in excess of 3-ft. However, pressurized injection into the shallow subsurface was not successful. Therefore direct chemical injection was only proposed for the deeper contaminant zone and an infiltration gallery was proposed for treatment of the more shallow soils. The RAP also proposed continued quarterly groundwater monitoring of monitoring well MW-5. The RAP was approved by WDNR in a letter dated December 19, 2018.
Installation of injection and gravity feed points, as well as the next quarterly sampling event, are scheduled to be completed in January 2019. The infiltration gallery is currently being constructed and initial chemical injection is tentatively scheduled for the beginning of February 2019. The results of quarterly groundwater sampling will continue to be reported to WDNR, and future DMRâs will be submitted on a monthly basis, as required under WPDES permit WI-0046566-07.
In addition to the remediation of the chlorinated contamination in the soil and groundwater, the Ace Hardware sump was sealed in September 2018, as requested by WDNR, and construction of the water treatment system for the sump water is currently underway. An application for discharge of the treated sump water under WPDES permit WI-0046566-07 is being prepared and will be filed with the SER Wastewater Program.
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