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The site investigation was continued following the approved Site Investigation Workplan (SIWP), submitted by Tetra Tech on October 15, 2021. Concurrence was received from the WDNR in a letter dated March 9, 2022.
During July and August 2022 step out samples were collected to define the vertical and horizontal boundaries of the soil contamination related to the GAC spill as per the SIWP.
On October 25, 2022, Tetra Tech submitted a Site Investigation Report and Remedial Action Plan (RAP). This report summarized the site investigation including the sampling methods and results and rationale for defining the contamination boundaries. The RAP described the planned remedial actions.
The RAP was implemented during November 2022. The site excavated the contaminated soil defined by the site investigation following the procedure in the RAP. Confirmation samples were collected at the bottom of the excavations. The results were analyzed and concentrations were below the clean-up standard, which is the NR720 RCL of 3.13 mg/kg for total mercury. Excavated soil was placed into lined roll-off containers and sent for disposal at a hazardous waste disposal facility. A remedial action report is to be completed and submitted in 2023.
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