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implemented. However, the frequency and timing of follow-up sampling may also be guided by the initial concentrations of VOCs detected in accordance with October, 2015 DTSC Human Health and Ecological Risk Office, Human Health Risk Assessment Note Number 3 and August 23, 2014 DTSC Human Health and Ecological Risk Office, Human Health Risk Assessment Note Number 5 (discussed in Section 7.0). The samples will be analyzed by Modified Method TO-15 Selective Ion Mode. 6.3.2 Proposed Sub Slab Soil Gas Probe Installation Methods The proposed sub-slab soil gas assessment will be conducted in general accordance with the July 2015 DTSC document titled Advisory-Active Soil Gas Sampling (Advisory). The three proposed sub-slab soil gas sample locations within the interior of the Quality Cleaners as shown on Figure 6. One sample will be proximate to the floor drain in the boiler room and the location of the December 2014 sub-slab soil gas sample SGI, a second sample will be proximate to the dry cleaning machine and December 2014 sub-slab soil gas sample SG2, and a third sample will be within the southwestern portion of the dry cleaners suite and proximate to the inferred location of the sewer lateral. The permanent soil gas probes will be secured and completed to prevent infiltration of water or ambient air into the subsurface and to prevent accidental damage or vandalism. The tubing will be marked at the surface to identify the probe location and depth. A gas-tight valve or fitting for capping will be affixed to the sampling tube. The sub-slab soil gas samples will be collected and analyzed for VOCs in accordance with EPA Method 8260 by on-site mobile laboratory using gas-tight glass syringes which will allow the analytical results to be available within approximately 30 minutes after the samples are collected. A five-foot deep soil gas probe will be installed proximate to the location of the sub-slab soil gas sample that has the greatest detection of PCE and/or TCE. This probe would be installed as described in Section 6.4. The sub-slab soil gas probes and five-foot deep soil gas probe will be permanently installed and secured with flush mounted fittings and a well box, respectively. Probe destruction methods will be provided in an additional work plan upon completion of onsite activities. 6.4 Proposed Site Boundary, Sewer Lateral, and Petroleum Hydrocarbon Release Soil Gas Assessment Proposed soil gas samples will be collected from four 5-foot deep soil gas probes along the southern boundary of the Site. The four soil gas probes will be installed as shown on Figure 7. 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 23