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January21, 2026 Zachary Walton, Partner Proposal for Supplemental Environmental Support Services at 1010 Industrial Drive, Stockton, California Following completion of sampling activities,the boring will be over drilled with a 6-inch diameter hollow stem auger to facilitate installation of a 2-inch diameter monitoring well.The groundwater monitoring well will be installed with a total depth of 30.5 feet bgs with 10 feet of factory-slotted well screen and a 6-inch sump from 30 to 30.5 feet bgs. A sand filter pack will be placed in the annular space from the bottom of the well to 2 feet above the top of the screen, a 2-foot-thick bentonite transition seal will be placed on top of the sand, and grout will be placed from the top of the bentonite seal to the surface.The well will have a flush-mount,traffic-rated well box for the surface completion.The completed well will be developed by surging, bailing, and pumping at least 48 hours after installation. The well will be surveyed following groundwater monitoring well installation. At a step out location to the groundwater monitoring well, a boring will be advanced to a total depth of 5.5 feet bgs via hand auger to install a soil gas well. Soil will be logged and screened for the presence of VOCs with a PID. The soil gas well will be installed with 1/4-inch Nylaflex tubing with a 1-inch-long stainless-steel screen at 5 feet bgs.The probe tip will be set within a minimum of 6 inches of sand,followed by a minimum of 6 inches of dry bentonite and a minimum of 6 inches of hydrated bentonite. Neat cement grout will be placed on top of the bentonite to fill the remainder of the annular space to a depth of approximately 1 foot bgs.At the ground surface,the well will have a traffic-rated well box and the 1/4-inch-diameter Nylaflex tubing will be fitted with an airtight valve using a compression fitting for subsequent attachment to the sampling train. The groundwater monitoring well and soil gas well will be completed in accordance with State and Local requirements and protected with a locking well vault or monument. Groundwater Monitoring Well Sampling New and previously installed groundwater wells will be sampled using a low-flow micro-purging technique in accordance with U.S. Environmental Protection Agency guideline (USEPA 2017) and Terraphase SOP 205-23-00, "Groundwater Sampling—Low Flow", included in Attachment C. A total of four samples will be collected, including one duplicate sample and one trip blank, and submitted to a California-certified analytical laboratory under chain-of-custody protocol for the following analysis: • VOCs by USEPA method 8260B; — Trip blanks will only be analyzed for VOCs; • pH using EPA 150.1; • Nitrogen as Nitrate using EPA Method 300.0; • Nitrate as Nitrate using EPA Method 300.0; • Chloride using EPA Method 300.0; • Residual chlorine using Standard Method 4500-CL-G; and • Dissolved metals (22 CCR 66261.24) using EPA Method 601013/7470A. 41 Page 3 of 7