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Additional Soil Vapor Assessment Work Plan Page 6 CPSA,Lodi,California March 22,2024 212 W. PINE STREET PROPERTY CHT, on behalf of the City, proposes to perform the following activities to further delineate and define the extent of the residual PCE plume in soil vapor beneath and in the parking area behind the 212 W. Pine Street building— • Install temporary soil vapor (TSV) probes and perform discrete depth soil and soil vapor sampling at two locations behind the 212 W. Pine St. building— one outside the building near the location where the highest SS PCE concentrations (SS-5) were observed and the other near the intersection of the sewer lateral emanating from the building and the main sewer lateral in the alleyway; • Install one (1) sub-slab sample probe in Tenant Space 3 beneath the slab in the building; and, • Collect one (1) indoor air samples in the building and one (1) ambient air sample from outside the building wall facing the alleyway DISCRETE DEPTH SOIL VAPOR SAMPLING CHT will perform discrete depth soil and soil vapor sampling at locations SV-3 and SV-4 (Figure 4)to delineate the vertical extent of the PCE and TCE in soil vapor along the sewer lateral emanating from the building. The proposed soil vapor sampling locations would help us identify if the existing sewer lateral is acting as a continuing source for the residual PCE in soil. Methodology Prior to installation of the TSV probes, CHT proposes to install soil borings at SV3 and SV4 to a depth of 40 to 45 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. TSV probes will then be installed near SV3 and SV4 in accordance with the DTSC's Advisory- Active Soil Gas Investigations (DTSC, 2012). The TSV probes will be installed using a dual-purpose limited access rig. At each soil vapor sampling location, the drill rig will advance the rods to a total depth of 40 to 45 ft-bgs in one boring where the 40 or 45-foot TSV probe will be installed, and then drill separate borings for installing the TSV probes at depths of 5, 10, 15, and 25 ft-bgs. The exact depth of the TSV probes will be determined from the soil core samples. Each TSV 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. To ensure that representative soil vapor samples are collected for each specified depth, 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. 581 MONTEGO TERRACE,SUNNYVALE,CA 94089 TEL:415-424-3009