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Geospte& consultants Soil samples to be analyzed for TPH-d and TOC will be collected directly from the stainless steel or acetate liner and placed into laboratory-supplied glass jars. Samples will be labeled, handled, and analyzed as described in Section 3.2.2. Sample container requirements, holding times, and preservation requirements are outlined in Table 3. If groundwater is encountered during drilling activities, a 2-inch temporary casing with a 5-foot screen interval will be installed in the boring following the collection of the soil samples. The groundwater will be allowed to equilibrate within the casing. It will be assumed that equilibration has been achieved when the depth to groundwater stabilizes. To assess for the presence of LNAPL in the temporary casing, an oil-water interface probe will be lowered through the casing. If LNAPL is present, Geosyntec field personnel will attempt to measure the relative thickness of the LNAPL. A sample of the LNAPL will also be collected using by lowering a clean, disposal bailer into the casing to retrieve a LNAPL sample. The LNAPL samples will be collected into laboratory-supplied sample containers. Grab groundwater samples will then be collected from each temporary casing. A discrete interval groundwater sampler will be lowered into the casing to the approximate mid-point of the water column. Once a grab groundwater sample is retrieved, the sampler will be removed from the casing. One field duplicate groundwater sample will be collected for analysis of VOCs, TPH-g, and TPH-d. One trip blank will be submitted to the laboratory for analysis of VOCs. The grab groundwater samples (including the groundwater duplicate) will be placed into laboratory-supplied containers. Samples will be labeled, handled, and analyzed as described in Section 3.2.2. Sample container requirements, holding times, and preservation requirements are outlined in Table 3. In accordance with San Joaquin County Environmental Health Department's Site Mitigation Well and Boring Permit conditions,boreholes will be backfilled with type I/II Portland cement. A grout inspection will be scheduled with a San Joaquin County Environmental Health Department inspector who will observe borehole backfilling. 3.2.2 Sample Labeling, Handling, and Analysis Samples will be labeled, handled, and analyzed as presented below. 3.2.2.1 Sample Identification and Handling Each sample will be assigned a unique alphanumeric identifier. The identifier will be formatted as "Project Identifier-Location-Depth-Date"using the following information: • The project designator will be "PS-UST,"to denote Port of Stockton UST sites. • The location will correspond to sample locations shown in Table 2. • The depth will indicate the top depth in feet bgs. • Date of collection will be in the form of YYYYMMDD. Final Investigation Work Plan Addendum—UST 817B 6 June 24,2022