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Soil Vapor Assessment Work Plan Page 8 CPSA,Lodi,California January 11,2023 210 W. PINE STREET PROPERTY CHT, on behalf of the City, recommends collecting two indoor air samples (IA-7 and IA-8 in Figure 4) as part of the post-closure and decommissioning of the CPSA GWET and SVE systems activities. The sample collection methodology will be similar to the one described above for the 212 W. Pine St. property. 18 S. PLEASANT AVENUE RESIDENCE - PSG SAMPLING As part of the decommissioning of the CPSA GWET and SVE system,the City performed a limited excavation of soil containing elevated VOCs along the sewer line in the alleyway near the intersection with S. Pleasant Avenue (Figure 2). Additionally, the sewer segment in that stretch of excavation was also replaced by the City. The excavated area, which extended all the way to the northern property boundary of the 18 S. Pleasant Ave. residence, was backfilled with clean aggregate following completion of excavation activities. Results of the post-closure February 2022 indoor air monitoring event indicated that the 18 S. Pleasant Ave. residence indoor air sample had PCE concentrations in indoor air (7.60 µg/m) greater than the PCE residential indoor air ESL value of 0.46 µg/m3. However, these concentrations could not be confirmed as CHT was denied access by the owner to perform verification and additional sampling in both June and October 2022, respectively. The City proposes to install two (2) PSG samplers outside the residence to determine the presence residual PCE, if any, in soil vapor that may be contributing to the presence of PCE in indoor air at the residence. As shown on Figure 5, the proposed PSG sample locations are on S. Pleasant Ave. (western part of the residence) and the parking lot along the eastern boundary of the residence. No PSG samples are proposed in the alleyway next to the residence as the PSG samplers would be installed in the aggregate base of the excavation and would not provide any measurable results. CHT proposes to install the PSG samplers using the Beacon BeSure Sample Collection KitsTM At each location, a hand-held rotary hammer will be used to drill a 11/4"- to 11/2"-diameter hole through concrete/asphalt/gravel to a depth of approximately 12-14 inches below grade. After completing the hole, a'/2"drill bit will be applied using the hand-held rotary hammer to extend the hole to a three-foot depth. Following the completion of the hole, a 12-inch length of 1"-diameter metal pipe will be lowered into the sample hole. PSG samplers, which are comprised of a glass vial containing two sets of hydrophobic adsorbent cartridges and a black one-hole cap with a screen meshing insert, will then be lowered, with the cap-end facing downward, approximately 4 to 6 inches within the pipe in each hole. The hole will first be plugged with a wad of aluminum foil so that it forms a seal on the metal pipe. The ground surface will then be temporarily patched with a 1/4" thick concrete patch using a dry concrete mix. 649 DISTEL DRIVE,LOS ALTOS,CA 94022 TEL:415-424-3009