COMPLIANCE INFO_EW-5 INSTALL PERMIT PACKAGE 2/14/25

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WELL INSTALLATION AND INTERIM REMEDIAL ACTION REPORT www.arcadis.com FINAL_Forward CHCF (CDCR) Well Installation Report_10182024 16 The predicted capacity and groundwater capture parabola estimation for the proposed additional extraction well was based on review of the boring logs for monitoring well AMW-50M and extraction well CDCR-EW-3, including interpretation of the geology and thickness of permeable materials. Based on this review, the proposed additional well extraction capacity and capture is anticipated to be similar to extraction well CDCR-EW-3, with a maximum pumping rate of 35 gpm and upgradient capture width of approximately 492 feet. Calculated groundwater capture with the additional proposed extraction well (CDCR-EW-5) is presented on Figure 7. Therefore, an additional extraction well at this location is required for complete capture of the CDCR TVOC plume with concentrations of 25 µg/L or greater. The maximum extraction capacity for all wells is predicted to be approximately 140 gpm but overlapping well capture parabolas indicate that a lower extraction rate might still achieve complete TVOC plume capture. Flow balancing will be performed upon the GWET system startup. In summary, installation of the additional extraction well is proposed as follows: • Extraction well CDCR-EW-5 is proposed to be installed at the location presented on Figure 7. Well design specifications are presented in Table 17 and a well construction diagram presented in Appendix I. • The logging and installation methodology will follow the work plan for previous extraction well installations (Arcadis 2023a), as detailed in the following sections. One exception is that step and constant rate hydraulic testing are not proposed for this additional extraction well because sufficient hydraulic data are available from the extraction wells already installed. Hydraulic measurements will be collected during the pumping phase of well development of the proposed extraction well to enable estimation of the well’s specific capacity and sustainable pumping rate. These data will be used for pump specification and radius-of-influence estimation. 5.5.1 Drilling Details The expanded scope of work includes the installation of an additional extraction well, CDCR-EW-5 (Figure 7). A State of California C-57 licensed driller will be used to advance the boring and construct the extraction well. All drilling and well construction will be completed in general accordance with the requirements specified in California Well Standards (California Department of Water Resources (DWR) Bulletins 74-81 and 74-90 [DWR 1981, 1990, respectively]) under the supervision of a California Professional Geologist. The groundwater extraction well will be drilled with the appropriate drilling technology for the depth and diameter of installation, lithology, and required well design (likely hollow-stem auger, sonic, or air rotary drilling techniques). The borehole diameter will be at least 2 inches larger than the final outside casing diameter, and the well will be installed to approximately 130 feet bgs in the intermediate groundwater WBZ. The targeted drilling depth may be modified in the field based on the soil conditions encountered during drilling. Arcadis field personnel will describe the soil using the Unified Soil Classification System and will identify potential production intervals and confining layers/aquitards. Continuous soil sampling will be conducted from the water table down to the target depth. Soil sampling equipment will be decontaminated between each sample collected , and drilling (rods and/or auger flights) and sampling equipment will be decontaminated between each borehole advanced. Decontamination will include a triple rinse of sampling devices and pressure washing (or equivalent) of drilling equipment between drilling locations. The extraction well design will be aided by the lithologic conditions logged during drilling and the collection of soil samples from an initial pilot hole. Soil samples will be collected from the intermediate WBZ for sieve analysis from the potential extraction well screen interval and will be used for the well slot size and filter pack design. After the extraction well has been designed and the well materials are sourced, the extraction well will be installed.