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Mr. Brenden Kenny <br /> Central Valley Regional Water Quality Control Board <br /> March 7, 2022 <br /> • CDCR-SB-02: Further define VOC impacts to groundwater and soil vapor hydraulically downgradient of <br /> 7833 Newcastle Road and in the vicinity of the CDCR's main sewer outlet to the City of Stockton sanitary <br /> system along the western boundary of the CDCR property. <br /> • CDCR-SB-03: Further define VOC impacts to groundwater and soil vapor hydraulically upgradient of <br /> 7833 Newcastle Road. <br /> • CDCR-SB-04: Investigate VOC impacts to groundwater and soil vapor in the vicinity of the former laundry <br /> facility and the CDCR's central stormwater and sewage collection pump/area. Additionally, this proposed <br /> location is located approximately 630 feet hydraulically downgradient of AMW-22. <br /> • CDCR-SB-05: Investigate VOC impacts to groundwater and soil vapor in the vicinity of AMW-22. <br /> Additionally, this proposed location is located approximately 860 feet hydraulically upgradient of AMW-22. <br /> The direct push drill rig will advance CPT borings CDCR-SB-02, CDCR-SB-03, and CDCR-SB-05 to <br /> approximately 120 feet below ground surface (bgs). The CPT measures cone tip resistance, sleeve friction, and <br /> other parameters, from which the corresponding stratigraphic soil profile can be interpreted (e.g. sand, silt, clay). <br /> Advancement of the CPT borings will be performed by a California licensed driller and overseen by an <br /> experienced geologist under the direct supervision of a California Professional Geologist or Professional Civil <br /> Engineer. <br /> Up to two groundwater samples will be collected from each of the CPT locations using HydropunchTM <br /> methodology and analyzed for VOCs using the United States Environmental Protection Agency (USEPA) Method <br /> 8260B by a state certified laboratory. The groundwater samples will be collected from higher hydraulic <br /> conductivity zones based on Arcadis geologist's interpretation of the CPT results (e.g. tip stress, sleeve friction, <br /> and pore pressure). Based on grab-groundwater data collected in the first phase, permanent groundwater <br /> monitoring wells may be installed to assess shallow groundwater conditions. Soil samples will not be collected <br /> during the first phase but may be collected at pre-selected locations/depths during subsequent phases of <br /> investigation to install the permanent monitoring wells. <br /> Multi-depth soil vapor probes will then be installed via a direct-push rig at the 5 boring locations with probes <br /> installed at depths of approximately 5, 15, and 45 feet bgs. Probe construction and sampling details are provided <br /> in the Work Plan (Arcadis 2019). <br /> Additional Phase(s)—Adaptive Investigation <br /> Following the first phase of the SI, additional SI phases will largely utilize an adaptive approach to select step-out <br /> boring locations and collect additional groundwater and soil vapor samples, and potentially soil samples, to fill <br /> remaining data gaps following the first phase of SI. Because this is purely an adaptive phase of work, the <br /> additional step-out sampling locations are not known at this time. Weekly updates on the progress of the SI will be <br /> provided to the RWQCB and other stakeholders, and planning for the additional SI phases will involve stakeholder <br /> collaboration. <br /> www.arcadis.com 7/9 <br />