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Soil Vapor Assessment Work Plan Page 6 CPSA,Lodi,California January 11,2023 SUB-SLAB SAMPLING In order to assess the potential vapor intrusion in the 212 W. Pine Street building, up to six (6) semi-permanent sub-slab soil gas Vapor Pins® (or equivalent)will be installed below the concrete slab of the building in a manner consistent with DTSC guidance. The proposed sampling locations of the Vapor Pins® (SS-1 through SS-6), as depicted on Figure 4, were chosen to provide an assessment of soil vapor conditions beneath the entire building as well as to target specific areas where a release may have occurred (for example near the floor drain, along the sanitary sewer lateral). Standard Operating Procedures for Installation and Use of the Vapor Pins, which were obtained from the manufacturer/distributor of the devices, are provided in Attachment A. PROPOSED SOIL VAPOR PIN INSTALLATION& SAMPLIN, IETHODOLOGY At each proposed location, a temporary sub-slab soil Vapor Pin® 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 samples will follow the procedures in Cal/EPA's 2012 Active Soil Gas Investigation Advisory, which recommends leak testing and shut-in testing. After installation, each sub-slab soil Vapor Pin®will be sampled using the following procedures: • Samples 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 each 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, each Vapor Pin® and sampling apparatus will be purged of three volumes of air inside the sampling assembly including tubing; 649 DISTEL DRIVE,LOS ALTOS,CA 94022 TEL:415-424-3009