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WORK PLAN FOR ADDITIONAL SITE INVESTIGATION Irerracon Vacant Property Tracy, California April 16, 2021 Terracon Project No. NA197074B Additional soil samples may be selected for delivery to the analytical laboratory. However, these soil samples will be placed on hold for potential contingent analyses, if recommended based on review of the initial soil sample analytical results. The soil samples will be collected into laboratory-prepared containers. The containers will be labeled and placed on ice in a cooler. The soil samples and completed chain-of-custody forms will be transported to a State of California-certified laboratory for analysis. Groundwater Sampling Following drilling and sampling to depths where soil impacts from the release are no longer evident in the soil boring for SB18, the boring will be extended to approximately 60 using the hollow-stem auger capability, if required, to complete this boring as a temporary sampling well (TSW) for the collection of a groundwater sample. The TSW will be constructed by installing 5 feet of 1-inch diameter, 0.010-inch machine slotted PVC well screen with a threaded bottom cap, with 1-inch diameter, threaded,flush-joint PVC riser pipe to surface.The TSW will be left in-place long enough to allow time for enough groundwater to accumulate and be sampled. The groundwater sample from the TSW will be collected using a new disposable polypropylene bailer or low flow sampling equipment and new disposable tubing. The groundwater samples will be collected into laboratory-prepared containers. The containers will be labeled and placed on ice in a cooler. The samples and completed chain-of-custody forms will be transported to a State of California-certified laboratory for analysis. 2.2.4 Boring Abandonment Terracon will schedule the backfilling inspection with the SJCEHD no later than 48 hours prior to planned field work activities to ensure the availability of an SJCEHD representative. Additionally, Terracon will confirm the field work date and inspection time with the inspector 24 hours prior to field work. At the completion of sampling activities and in the presence of an SJCEHD representative,the soil borings will be backfilled using neat cement. A tremie pipe will be lowered to within three feet of the bottom of the boring and the cement slurry will be deposited into the borings via the tremie pipe. The proposed sampling locations may be modified in the field to account for access limitations and/or site conditions. The client will be notified of any significant modifications to the sampling locations. The sampling and analytical program are summarized in Table 1 below. Details on sample collection and handling procedures are provided below. Responsive■ Resourceful ■ Reliable 6