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09 October 2023 AdvancedGeo Project No. 23-7573 CLIENT —ATTORNEY PRIVILEGE An Employee-Owned Company Page 3 of 5 All appropriately sealed and labeled samples will be placed in a chilled container with ice and transported under chain-of-custody procedure to a California Environmental Laboratory Accreditation Program (ELAP)-certified laboratory. Each sample will be labeled with boring designation, depth, time, date, and sampler's initials. Soils encountered in the borings will be visually classified by AGI personnel in accordance with the Unified Soil Classification System (USCS). Field screening of soil samples shall be performed using an organic vapor meter (OVM), equipped with photo-ionization detector (PID) pre-calibrated to isobutylene. Soil samples will be analyzed for Volatile Organic Compounds (VOCs) in accordance with EPA method 8260B. 2.2. SOIL-VAPOR POINT INSTALLATION, SAMPLING AND ANALYSIS AGI proposes to install eighteen (18) soil vapor points at the site, within twelve (12) of the completed borings. Following soil sample collection at the deepest proposed locations (15 feet bsg), dual completed wells will be installed in each of the locations. A total of 17 feet of/4-inch diameter Teflon® tubing and a 2-inch-long polyethylene soil-vapor implant will be lowered to the bottom of the borehole. A filter pack of#2/12 sand will be added to approximately 14 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 13 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void to 5 feet bsg. At 5 feet bsg a total of 7 feet of '/4-inch diameter Teflon® tubing and a 2-inch-long polyethylene soil-vapor implant will be lowered to 5 feet bsg. A filter pack of #2/12 sand will be added to approximately 4 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 3 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void to near surface grade to prevent ambient air intrusion. For the five proposed 10-foot vapor sampling locations, the direct push rods will be advanced to the total proposed depth and soil samples will not be collected. Once the total depth is reached a total of 12 feet of diameter Teflon® tubing and a 2-inch- long polyethylene soil-vapor implant will be lowered to 10 feet bsg. A filter pack of#2/12 sand will be added to approximately 9 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 8 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void to near surface. Following soil-vapor well installations, a minimum 2-hour stabilization period will be observed prior to soil-vapor sample collection from the vapor points. For sample collection, a one-liter Summa canister and 60ml purge syringe will be connected with a dedicated and serialized sampling inlet manifold to the vapor point tubing. The sampling inlet manifold will consist of an air/vapor-tight valve; a particulate filter; a flow restrictor calibrated to 150 milliliters per minute (ml/min), a stainless-steel tee-fitting, two vacuum gauges at either end of the controller and connections for both purge syringe and sampling canister (manifold assembly). Prior to sample collection, each soil-vapor well