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Soil Vapor Sampling Work Plan Page 4 LSP Area,Lodi,California October 13,2021 CHT will perform discrete depth soil vapor sampling at locations LSP-SV 1 and LSP-SV2 (Figures 3 and 4) to delineate the vertical extent of the PCE and TCE in soil vapor. The proposed soil vapor sampling locations are at the two locations south of the industrial pump station where the highest PCE and TCE concentrations were observed during the LSP PSG sampling events. Prior to installation of the temporary soil vapor probes, CHT proposes to install soil borings at LSP-SV1 and LSP-SV2 to a depth of 50 feet below ground surface (ft-bgs) using continuous soil coring. The soil cores, which will be collected in acetate liners, will be used to log the soil, and determine the screen intervals for all of the targeted temporary soil vapor probe depths. Temporary soil vapor probes will then be installed near LSP-SV1 and LSP-SV2 in accordance with the DTSC's Advisory- Active Soil Gas Investigations (DTSC, 2012). The temporary soil vapor sample probes will be installed using a dual-purpose limited access rig which is capable of advancing either hollow stem auger or drill push drilling rods. The direct push option will be employed first, and hollow stem augers used if refusal is encountered using the direct push option. At each soil vapor sampling location, the drill rig will advance the rods to a total depth of 10 ft-bgs in one boring where the 5 and 10 ft soil vapor probes will be installed, and then drill separate borings for installing the soil vapor probes at depths of 20, 30, and 50 ft-bgs. Each soil vapor probe will be constructed with a 1-foot long filter pack in the bottom of the borehole consisting of#2/12 Cemex sack sand. A 0.250-inch outside diameter(0.187-inch inside diameter) polyethylene tube with a HDPE filter at the bottom of the tube will be placed in the center of the borehole during placement of the sand so that the HDPE filter is located in the center of the sand interval. The annular space above the sand will be temporarily sealed using hydrated bentonite slurry that will be pumped down the hole using tremie pipes to a height of 0.5 feet above the top of the sand. This would ensure that representative soil vapor samples are collected for each specified depth. The soil gas samples will be collected in accordance with the sampling protocols established in the Advisory (DTSC, 2012). Soil gas samples will be collected in individual certified 1-liter SummaTM canisters where the SummaTM canister will supply the vacuum to draw soil gas into the canister for analysis. The temporary soil vapor probes will be purged and sampled in accordance with Section 4 (Soil Gas Sample Collection) and leak detection will be performed in accordance with Section 4.2.2.1 (Leak Check Compounds [Liquid]) of the Advisory. CHT proposes to use helium as the leak detection compound. Following soil vapor sample collection, a PID will be connected to the polyethylene soil vapor probe tubing to obtain a preliminary field value for the sample collection location. Measurements of vacuums, purging and equilibration time intervals, and PID readings will be recorded on Soil Vapor Sampling Data Sheets. The SummaTM canister soil vapor samples will be delivered under chain-of-custody protocols to a California-certified laboratory for testing by EPA method TO-15 analysis for chlorinated VOCs. Additionally, the leak detection compound (helium) will be analyzed using EPA Method TO-3. 175 N EL MONTE AVENUE,LOS ALTOS,CA 94022 TEL:415-424-3009