ARCHIVED REPORTS_SECOND SEMIANNUAL 2018 GROUNDWATER MONITORING REPORT

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Second Semiannual and 2018 Annual Groundwater Monitoring Report JACOBS® 2. Results for Second Semiannual Period 2018 This section presents the groundwater monitoring results for the second semiannual period for 2018, the • status of remediation and other completed activities for the second semiannual period for 2018, and planned activities for the next semiannual monitoring period. 2.1 Groundwater Monitoring The following groundwater monitoring activities were performed in the second semiannual period for 2018 • (April through September 2018), in accordance with MRP No. R5-2018-0806. • 0 Depth to groundwater was measured on September 7, 2018, in 15 shallow (less than 25 feet below ground surface [bgs]) onsite groundwater monitoring wells and in 1 deeper(greater than 35 feet bgs) onsite groundwater monitoring well. • Groundwater samples were collected on September 7, 2018, from all 13 shallow wells scheduled to be sampled and the 1 deeper well scheduled to be sampled. • Groundwater and quality assurance (QA) samples were analyzed by a state-certified laboratory. 2.1.1 Methods • The following wells were gauged and sampled: Order .. 1 Upgradient wells: M-1 and M-3a Single-Phase Probe 2 Sentinel wells: M-8, N-18, N-19,and N-20 Single-Phase Probe 3 Deep well: N-24 Single-Phase Probe 4 Plume fringe wells: M-10, N-8, and 0-1 Single-Phase Probe 5 Plume wells: N-7,N-15,N-16, N-17,and RW-1 Single-Phase Probe a Well M-3 was gauged only and not sampled. The wells were gauged and sampled in the order indicated above (from cleanest to most contaminated) to minimize the potential for cross-contamination. Figure 2 shows the locations of the wells. Table 1 presents a summary of the construction details of the wells. 2.1.1.1 Field Methods Field gauging and sampling activities were conducted by Blaine Tech Services of Sacramento, California. • Copies of field notes from Blaine Tech Services are provided in Appendix A. Gauging The wells were gauged prior to sample collection. Depth to groundwater was measured using an electronic water-level meter. The measurements were made to the nearest 0.01 foot from a surveyed measuring point at each well location. Groundwater elevations were calculated by subtracting the depth to groundwater from the surveyed elevation at the surface of the measuring point. • Groundwater Sampling After gauging, groundwater samples were collected using HydraSleeve samplers as approved in a • November 10, 2011, email from the RWQCB to SFPP, except for two wells (M-8 and M-10) that were sampled using a bailer due to insufficient water to sample with a HydraSleeve. Blaine Tech Services • AX1015181035SCO