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Site Boundary Soil Gas Assessment Concurrent with the sub-slab soil gas and indoor air sampling, four soil gas samples will be collected from five-foot deep soil gas probes along the southern boundary of the Site immediately south and southwest of the Quality Cleaners. This work will be performed to assess the potential for the lateral migration of soil gas and to assess the potential for vapor intrusion into the residential structures along the southern boundary of the Site. Sewer Lateral Soil Gas Assessment Prior to the initiation of field activities, a geophysical survey will be performed to locate the sewer line on the Site. The geophysical survey will also check the proposed probe locations to ensure there are no underground utilities in proximity to the probes. Six soil gas samples will be collected from probes installed along the alignment of the sewer lateral connected to the Quality Cleaners. The depth of the probes will be at the depth of the sewer lateral as measured from sewer line cleanouts. The probes will be located in close proximity(i.e., approximately two feet)to the sewer laterals. This work will be performed to assess whether PCE may have been released from the sewer lateral. Groundwater Assessment Related to the Quality Cleaners At the completion of the soil gas sampling, five groundwater monitoring wells will be installed, developed, surveyed, and sampled to assess the potential impact to groundwater that may have resulted from the release of PCE from the Quality Cleaners. Groundwater samples will also be analyzed for the petroleum hydrocarbon dry cleaning solvent. These wells will be installed in locations to the south-southwest (upgradient) and north-northeast (downgradient) relative to the Quality Cleaners. These wells will be monitored to confirm the site-specific groundwater flow directions. Initially, three groundwater monitoring wells will be installed in a triangular array so that an expedited wellhead survey of the three monitoring wells can be performed. The results of the survey will be used to assess the flow direction of groundwater at the time the wells are installed. Based on the survey,the remaining two monitoring wells will be installed as proposed.If,however, the groundwater flow direction is other than to the north-northeast, the DTSC will be contacted so that alternative locations of the remaining two monitoring wells to be installed can be discussed. The vertical characterization of the PCE plume will occur in a separate mobilization following the confirmation of the groundwater flow direction and will consist of continuously cored direct push soil borings and the collection of grab groundwater samples from targeted strata. As currently envisioned, up to five pairs of 35-foot deep direct push Geoprobe borings would be advanced at Sampling and Analysis Workplan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 19