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Geosyntec consultants 5.3 Sampling and Analysis Wells sampled for VOCs will be analyzed by USEPA Method 8260B (Table 3). Wells that had concentrations of TPHg or TPHd greater than 100 µg/L during the most recent groundwater monitoring event or wells that define the extent of TPH as greater than 100 µg/L in groundwater will be sampled for TPHg by USEPA Method 8260B and TPHd and TPHmo by USEPA Method 8015B (Table 3). The new monitoring well planned to be installed in the Central Area will also be sampled for TPHg, TPHd, and TPHmo by the methods listed above (Table 3). Wells that had detections of dioxins and furans in 2020 above the laboratory reporting limits but concentrations below the laboratory reporting limits in 2021 will be sampled for dioxins and furans in 2022 by USEPA Method 8290. The new monitoring well planned to be installed at Site 3 will also be sampled for dioxins and furans (Table 3). Existing monitoring wells W-164, W-166, W-167, W-169, W-046, W-227, W-229 and W-048 and piezometers P-140 and P-146 will be sampled for radionuclides and potassium-40 (K-40)by USEPA methods 901.1, 903.0, 904.0 and 900.0. 5.3.1 Field Methods and Procedures All field work will be performed under the supervision of a California licensed professional geologist or engineer in accordance with the SOP for low-flow sampling provided in Appendix F and the Health and Safety Plan (HASP)provided in Appendix G. Confluence Environmental of Rio Linda, California(Confluence)will perform groundwater sample collection under the direction of Geosyntec using bladder pumps and the low-flow sampling methodology outlined in Appendix F. Samples collected from piezometers will be collected with peristaltic pumps consistent with past monitoring events, as the diameter of the piezometers do not allow for samples to be collected with a bladder pump (Geosyntec, 2019). The groundwater samples will be collected at a mid-screen depth in each well. Within each area, groundwater sampling will be conducted starting with the wells that have had the lowest VOC concentrations,with progressive sampling of the wells with higher VOC concentrations. Prior to and after each use, reusable sampling equipment will be properly decontaminated as described in the SOP in Appendix F. Quality assurance/quality control (QA/QC) samples will be collected in accordance with the Quality Assurance Project Plan (QAPP)provided in Appendix H. 5.3.2 Laboratory Methods and Procedures The groundwater samples will be sent under standard chain-of-custody procedures to TestAmerica Laboratories, Inc. of West Sacramento, California(TestAmerica), a California- certified laboratory, for analysis as listed in Table 3. The QAPP in Appendix G provides the reporting and method detection limits for specific analytes. 5.4 Investigation-Derived Waste Management Decontamination fluids and purged groundwater from sampling will be collected in 55-gallon drums,profiled for waste characteristics, and temporarily stored on-site. All investigative- derived waste (IDW) generated from the annual monitoring event will be removed off-site and disposed of by American Integrated Services of Wilmington, California (AIS). Once the IDW RRI Groundwater Monitoring Work Plan 19 June 2022