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Additional Soil Vapor Assessment Work Plan Page 8 CPSA,Lodi,California March 22,2024 • 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 a California-certified laboratory for testing for PCE and five breakdown products using EPA method TO-15SIM analysis for chlorinated VOCs. Additionally, the helium will be analyzed using Modified ASTM Method D-1946. INDOOR AND AMBIENT AIR SAMPLING As part of this ASVA, the City proposes to collect one (1) indoor air sample in the same room as sub-slab sample SS-6 (Figure 4). Prior to sampling, a survey of the indoor air location will be conducted to verify the proposed sample location, as well as to compile a list of chemicals used in the buildings that may represent potential cross contamination for the indoor air samples. Where possible, the following conditions will be imposed during the indoor air sampling: 581 MONTEGO TERRACE,SUNNYVALE,CA 94089 TEL:415-424-3009