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Proposed Remediation Well Installation Work Plan Stockton Charter Way Commingled Plume #CP0057 February 14, 2025 At the terminal depth of each well boring, an ART remediation 6-inch diameter well will be installed within the drill casing. Table 1 summarizes the anticipated well construction details for proposed remediation wells; however, these details may be modified in the field based upon the actual soil stratigraphy encountered. A sand filter pack will be placed in the annular space surrounding the entire screened intervals and will extend approximately two foot above the top of the screened interval. A bentonite annular seal will be placed and extend approximately two feet above the filter pack and hydrated as well as below the top screened interval. The remainder of the annular space will be filled with cement and/or grout from the top of the bentonite seal to within 12 inches of the surface. The wells will be temporarily secured with a locking well cap and completed with a watertight traffic-rated well box installed at grade. After a minimum of 48 hours following the well construction, the newly constructed wells will be developed to clean and stabilize the filter pack around the slotted well casings. Development will be accomplished by alternately surging each well with a vented surge block followed by pumping (using a submersible pump) to remove accumulated sediment. Final purging will be performed with either a submersible pump or bailer, and pH, temperature, and conductivity will be measured at regular intervals during purging. Development will be considered complete when: 1) eight well volumes have been removed and physical-chemical parameter trends have stabilized over three consecutive measurements (<0.05 pH, 3% conductivity, and 10% temperature); 2) ten well volumes have been removed; or, 3) the well has been purged dry (if the well does not sustain flow or is slow to recover). Following well construction, a licensed land surveyor or registered civil engineer will survey newly installed wells. The tops of casings of wells will be surveyed within the California State Plane Coordinate System for horizontal and vertical control to meet the State of California Water Resources Control Board requirements. The coordinates will be referenced to a known benchmark according to the North American Datum of 1983 (NAD83) and the North American Vertical Datum of 1988 (NAVD 88). 2.2.1 Soil Samples Soil samples will be screened in the field for the presence of VOCs using a PID, soil classifications, VOC measurements, sample intervals, and other pertinent geologic information. However, no samples will be submitted for laboratory analyses. 2.2.2 Waste Handling and Disposal Waste generated during the well installation activities will be stored on-Site in Department of Transportation-approved 55-gallon drums pending the results of laboratory analyses. Grab or composite samples will be collected as needed by the waste transportation or receiving facility. Analytical results will be used for waste profiling and disposal. After profiling, all waste will be transported and disposed of at an appropriate State-certified disposal facility. ® Stantec 4