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Mr. Brenden Kenny Central Valley Regional Water Quality Control Board March 7, 2022 and water levels will be measured as described above for the step-drawdown test procedures; however, the pumping rate will be kept at a single rate throughout the duration of the pumping portion of the test. The constant- rate pumping test will continue for up to 8 hours, and/or until water storage capacity has been reached. Logging of water levels will continue during the recovery period. Adjacent piezometers and monitoring wells (AMW-22 and AMW-22S)will be used as part of the constant rate test to observe the radius of influence in the shallow water bearing zone and to intermediate zones. Produced water will be pumped into a temporary storage container, likely a baker tank and transported to Forward Landfill for treatment and disposal. After completion of the constant-rate pumping tests, the water-level data will be downloaded from the pressure transducer data loggers for analysis. The hydraulic conductivity will be estimated using AQTESOLVTM software (Duffield 2007)with the Cooper-Jacob, Theis, or other appropriate curve fitting methods for unconfined aquifers. More complex methods, which account for well borehole storage or well skin effects, may be used if deemed necessary based on initial data analysis. Results of the pumping tests will also be used to evaluate hydraulic capture using methods contained in USEPA (2008)for analysis of capture zones. The interim treatment remedy described in the CAO R5-2017-0703 (RWQCB 2017) includes groundwater extraction and treatment, however other remedial method(s) could also be proposed and/or implemented, based on best design practice for the interim remedial design. If alternative remedial methodologies are necessary, then concurrence and approval of the RWQCB will be obtained prior to proceeding with further remedial actions. Typically, the remedial plan would include a determination of the source and extents of VOC mass prior to the installation of a treatment remedy; however, the RWQCB has requested the installation of the interim remedy prior to any additional source mass investigations on the CDCR Property. Implementation of the interim remedial design will follow Board approval in as efficient manner as is possible based on the technologies and/or methodologies selected. Considerations as part of the interim remedial design will include site and site area access, power requirements, potential movement of extracted groundwater and treatment facility positioning. CDCR Site Investigation As directed by the RWQCB, following installation of the interim remedial action on CDCR property, the first phase (Phase 1) of the SI will involve advancing Cone Penetrometer Testing (CPT) borings, then in response to the initial findings advance adjacent step-out borings, collecting groundwater grab samples from the shallow and intermediate aquifer zones and collecting soil vapor samples from nested probes installed at approximately 3 depths above groundwater in the vadose zone. Soil samples may be collected during subsequent phases of investigation based on the results of the initial groundwater and soil vapor samples. This Phase 1 scope of work will investigate the lateral and vertical extent of VOCs beneath the CDCR property by targeting potential sources of contamination, including the residential property at 7833 Newcastle Road, and the historical dry-cleaning facility located on the CDCR property. Phase 1 —Potential Source Area Investigation The five proposed boring locations for the first phase of investigation are shown on Figure 2. The rationale for the placement of these proposed locations is the following: • CDCR-SB-01: Investigate VOC impacts to soil vapor in the vicinity of AMW-22 and the adjacent main storm water drainage outlet for the CDCR property. www.arcadis.com 6/9