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Proposed Remediation Well Installation Work Plan Stockton Charter Way Commingled Plume #CP0057 February 14, 2025 present a Work Plan to describe and detail the proposed scope of work. For reference, Figure 1 presents a Site Location Map and Figure 2 presents a Site Plan with Proposed ART Well Locations. A figure showing the current and proposed ART remediation wells and piping layout is provided as Figure 3. Proposed Soil Boring and Well Construction Details are summarized in Table 1. Regulatory correspondence is provided in Appendix A. 2.0 PROPOSED ART WELL INSTALLATION Per the CRWQCB-CVR letter (Appendix A), additional ART well installation is proposed to further remediate residual MTBE at the Site (Figure 4) and meet LTCP groundwater criteria. 2.1 PRE-FIELD ACTIVITIES 2.1.1 Health and Safety Stantec will generate a site-specific Health and Safety Plan (HASP) or equivalent RMS-1 for the proposed scope of work as required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120). The document will be reviewed and signed by all onsite consulting personnel and subcontractors prior to performing work at the site. 2.1.2 Permitting and Utility Clearance Prior to conducting subsurface work, a subsurface drilling permit will be obtained from San Joaquin County Environmental Health Department (SJCEHD). Underground Service Alert (USA) will be contacted to delineate subsurface utilities near the proposed boring locations with surface markings, and a private utility locator service will be contracted to clear the area. An air knife will be used to safely excavate shallow soil down to approximately six (6) feet below grade to clear for potential underground utilities and other obstructions prior to drilling. 2.2 PROPOSED WELL INSTALLATION DETAILS A total of two ART wells will be installed in accordance with SJCEHD Well Standards and permit requirements. Each boring will be advanced using a sonic drilling rig equipped with heavy- walled down-hole 12-inch casing telescoped to help seal off shallower groundwater-bearing zones. Cores will be evaluated for continuous soil stratigraphy. Soil cores will be classified using the Unified Soil Classification System under the direction of a State of California Professional Geologist. Soil cores will be screened in the field for the presence of volatile organic compounds (VOCs) using a photo-ionization detector (PID). Soil classifications, VOC measurements, sample intervals, and other pertinent geologic information will be recorded on soil boring logs. Down- hole drilling equipment will be decontaminated with high pressure steam following the completion of each soil boring. Down-hole sampling equipment will be decontaminated between samples using an Alconox detergent solution and a tap water rinse. Decontamination water will be collected within a decontamination pad and will be containerized in drums for subsequent disposal. 5 Stantec 3