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Discrete Depth Soil&Soil Vapor Assessment Work Plan Page 5 CPSA,Lodi,California March 12,2025 Soil and Soil Vapor Sampling A total of ten(10)to twelve(12) soil samples will be collected from borings SP-1 and SP-2 using the Terra Core® sampling tool/method as described in United States Environmental Protection Agency(USEPA) SW-846 Method 5035. Soil samples will be collected from the acetate liners for each boring at depths of 5, 10, 15, 25, and 40 ft-bgs. The collected soil samples will be labeled, placed on ice, and handled under standard chain-of- custody procedures for delivery to Eurofins,a California-certified laboratory and analyzed for VOCs using EPA Method 5035/8260B. The description of Terra Core®samplers and the methodology for collection of samples using the samplers is provided in Attachment A. Ten (10) soil vapor samples will be collected in accordance with the sampling protocols established in the Advisory. Soil vapor samples will be collected in individual certified I-liter SUMMA® canister where the SUMMA® canister will supply the vacuum to draw soil vapor into the canister for analysis. The TSV 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 photoionization detector(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 SUMMA®canister soil vapor samples will be delivered under chain-of-custody (COC) protocols to AirToxics, 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 Modified ASTM Method D-1946. Upon completion of sampling activities, the TSV probes will be abandoned by removing temporary well points and sealing the borehole with a neat cement grout or by using the appropriate method approved by SJDEH, and under the supervision of an SJDEH inspector. INDOOR AND AMBIENT AIR SAMPLING As per the request of the Water Board,the City will prepare a sampling request to the owner of the 18 S. Pleasant Ave. property to conduct indoor air sampling. If permission is granted, the City proposes to collect one (1) indoor air sample in the residence and one (1) ambient air sample outside the residence on the back side near the alleyway (see Figure 3). 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 residence that may represent potential cross contamination for the indoor air sample. Where possible,the following conditions will be imposed during the indoor air sampling: • No smoking will be permitted in the subject building 4 hours prior to and during sampling. • To the extent possible, windows and doors should remain closed during sampling. 581 MONTEGO TERRACE,SUNNYVALE,CA 94089 TEL:415-424-3009