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REV: 08-14-25 LF Consultant shall grout the borehole to the surface in approximately 6-inch lifts with hydrated bentonite. Consultant shall place enough dry granular bentonite between the sand pack and hydrated bentonite grout to prevent infiltration of the hydrated bentonite into the sand pack. Consultant shall fit a valve to each of the aboveground ends of the tubing, which will be kept closed prior to purging and sampling. Consultant shall install 6-inch diameter, watertight, flush mount, traffic rated well boxes for the soil vapor wells to allow for potential future sampling. Consultant shall install and sample soil vapor wells in accordance with applicable regulatory guidance. Once wells are installed, Consultant shall restore their work area to its original condition, which includes, but is not limited to, removing equipment and traffic control measures, cleaning any debris, restoring asphalt and concrete, or cleaning-up any landscaping. Consultant shall store investigation-derived waste, such as soil cuttings generated during the subsurface investigation, temporarily in a labelled 55-gallon steel drum at a location approved by the site property owners. Consultant shall use analytical results from composited waste soil samples to develop a waste profile and evaluate waste disposal options. Once Consultant has profiled the waste and selected a disposal option, Consultant shall coordinate disposal of the waste at an appropriate off-site facility. Task 3.3 – Soil Vapor Well Sampling Consultant shall collect soil vapor samples after a minimum of 2 or 48 hours, depending on whether the soil vapor well was installed by direct-push or auger method, respectively, to allow for the seal to set and surface conditions to equilibrate. Consultant shall connect the sampling apparatus to a flow regulator with an internal particulate filter, calibrated by the laboratory to 100 to 200 milliliters per minute. Consultant shall use a manifold collection system with an inline flow controller and vacuum gauge. Consultant shall conduct a shut-in test on the sampling train at each location to check for leaks in the aboveground fittings. Consultant shall observe the vacuum gauge on the train for 1 minute to determine whether vacuum pressure is dissipating. Following the shut-in test, Consultant shall conduct a standard 3-volume purge to empty the sampling train of ambient air from the sampling probes by using a dedicated purging Summa vacuum canister or vacuum pump. Consultant shall collect soil vapor samples using a helium shroud with analysis of helium gas as a leak check. Consultant shall collect soil vapor samples in 1-liter Summa canisters that will be maintained at ambient temperature and kept out of direct sunlight during handling and transport to the analytical laboratory. Consultant shall submit samples to a California certified analytical laboratory under standard chain-of-custody protocols. ATTY/AGR.2025.210/Farallon Consulting, LLC (Soil vapor investigation & groundwater sampling) (Page 13 of 19)