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Discrete Depth Soil&Soil Vapor Assessment Work Plan Page 7 CPSA,Lodi,California March 12,2025 Methodology At the proposed location, a temporary sub-slab soil Vapor Piny" will be installed using the following procedures— • A 5/8-inch diameter hole will drilled through the concrete slab and 1-inch into the underlying material to form a void; • Concrete dust and debris will be cleared from the resulting drilling with a shop vacuum and the subsequent hole cleaned with a bottle brush; • A Vapor Pin® will be placed into the 5/8 inch diameter hole and tapped into place with a dead blow hammer; and, • A secure stainless-steel cover will then be installed over the Vapor Pin The collection of sub-slab sample will follow the procedures in Cal/EPA's 2012 Active Soil Gas Investigation Advisory,which recommends leak testing and shut-in testing. After installation,the sub-slab soil Vapor Pin®will be sampled using the following procedures: • Sample will be collected a minimum of 2 hours after installation of the Vapor Pin® to allow for the subsurface to equilibrate; • A shut-in test will performed on the SUMMA® canister. The shut-in test will involve assembling the above ground sampling apparatus (including the SUMMA® canister and all valves, gauges, lines, and fittings). Then, the sampling apparatus will be evacuated to at least 100 inches of water using a purge pump, and a gauge on the apparatus will be observed for at least 1 minute. If there is no change in negative pressure, the shut-in test would have been deemed as passed and the sample will be collected without disassembling the apparatus; • Prior to sampling,the Vapor Pin®and sampling apparatus will be purged of three volumes of air inside the sampling assembly including tubing; • During purging and sampling, a shroud will be placed over the sampling equipment. Helium will be introduced into the atmosphere within the shroud to facilitate leak detection; and, • An individually clean-certified 1-liter SUMMA® canister equipped with a regulator to control the flow into the container to a rate of less than 200 milliliters per minute(ml/min) will be used to collect the samples. Once the samples are collected, the SUMMA® canister will be stored at ambient air temperature before delivery under COC protocols to AirToxics, a California-certified laboratory for testing for PCE and five breakdown products by EPA method TO-15 Hybrid analysis for chlorinated VOCs. Additionally, the leak detection compound (helium) will be analyzed using Modified ASTM Method D-1946. 581 MONTEGO TERRACE,SUNNYVALE,CA 94089 TEL:415-424-3009