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Notification—Soil Vapor Sampling—LSP Area Page 2 of 2 concentration of PCE and TCE in soil vapor were observed in an area south of the City's industrial pump station. Based on the results of the July and December 2020 PSG sampling events, the Water Board, in a letter to Andrew Richle with the City dated July 21, 2021, recommended a further course of action for performing additional investigation of the PCE and TCE in the soil vapors in the vicinity of the existing industrial waste pump station in the cul-de-sac. On behalf of the City, CHT prepared the Soil Vapor Sampling Work Plan (Work Plan) that identified the soil vapor sampling locations to assess PCE/TCE in deeper soil vapor where the highest concentrations were found in shallow soil vapor during previous PSG sampling, and the methodology for collecting soil vapor samples at discrete depths, and submitted to the Water Board on October 13, 2021. The Water Board approved the sampling locations proposed in the work plan in a letter to Andrew Richle with the City dated October 28, 2021. VTS Drilling (VTS) will use a dual-purpose limited access rig to perform the planned discrete depth soil vapor sampling to delineate the vertical extent of the PCE and TCE in soil vapor south of the City's industrial pump station at the LSP-SV1 and LSP-SV2 locations shown on attached Figure 2. VTS will begin by advancing soil borings to a depth of 50 feet below ground surface (bgs) using continuous soil coring to log the soil and determine the screen intervals for temporary soil vapor probe depths. CHT will then install temporary soil vapor sample probes at depths of 5, 10, 20, 30, and 50 feet bgs using the drill rig. VTS, under CHT supervision, will collect soil vapor samples from each probe in 1-liter individually certified Summa canisters using helium as the leak detection compound. The soil vapor samples will be delivered to a California-certified laboratory for testing of chlorinated volatile organic compounds by EPA method TO-15 and helium by EPA method TO-3. VTS will abandon the temporarily well points upon completion of sampling activities by removing temporary well points and sealing the borehole using the appropriate method approved by the San Joaquin Department of Environmental Health. If you have any questions or require any additional information, please contact me using my email or phone number below. Sincerely, Andrew Richle Utilities Superintendent (209) 267-4927 arichle@lodi.gov Attachments: Figures 1 and 2 CC: Via email Charles E. Swimley, Jr., Public Works Director—City of Lodi Varinder Oberoi, Civil Hydro Tech, LLC