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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California Each new well will have a new local control panel installed.The local control panel will follow the standard architecture currently deployed at South Balloon and Central Area well panels, consisting of a local programmable logic controller with standard discrete inputs and outputs and analog inputs to monitor and control the well pump. The programmable logic controller will monitor the water level and flow and report the data to the supervisory control and data acquisition system. 3.2.6 Surveying A professional California-licensed land surveyor will survey the newly installed wells for horizontal and vertical coordinates. Horizontal coordinates will be determined to the closest 0.01 ft and referenced to the State Plane Coordinate System, Zone 3, North American Datum of 1983. Ground surface elevations will be surveyed using the National Geodetic Vertical Datum of 1988 to the closest 0.01 ft. Elevations of the top of well casings will be determined. The measurement point on the casing will be clearly and permanently marked for future water level measurements. Following the fieldwork, maps will be prepared to show surveyed locations, elevations, and physical site features to confirm they are located correctly. 3.2.7 Sampling The newly installed wells will be added to the existing sampling well network and the groundwater sampled no sooner than two days after well development is complete. Groundwater will be sampled for VOCs using USEPA Method 8260C via low-flow sampling methods. The sampling frequency is based on the decision rules shown in the Well Sampling Frequency Decision Logic (Figure 15). Fieldwork will follow the guidelines, standards, and procedures documented in the QAPP (Ahtna, 2022b), APP (Ahtna, 2022c), Site Waste Management Plan (SWMP; Ahtna, 2022d), applicable SOPS (Appendix C), and this Work Plan. Field quality control samples will be used to assess the influence of sampling procedures, equipment,and handling on the reported results. To determine the final screen interval, discrete soil samples will be collected 5 ft above, 5 ft below, and at 5 ft intervals within the anticipated screen interval for each well, for lithologic description only. Soil samples will be logged in the field by a qualified geologist and by the Unified Soil Classification System. Professional judgement will be used to determine the final screen interval. Screen intervals will not be set in fine-grained sediments (i.e., clay). 3.3 Waste Management Solid and liquid IDW will be produced during the well installation activities and will be managed following the SWMP (Ahtna, 2022d). Soil IDW will be contained in labeled drums or bins adjacent to the well locations and then transferred to the Central Area GWTP.Soil IDW will be sampled and characterized to determine appropriate disposal by applicable laws and regulations, and an appropriate disposal facility will be identified following characterization. Excess soil that does not require offsite disposal will be transported to the soil spreading area west of the Central Area percolation ponds. Liquid IDW will be contained in labeled drums or tanks and, whenever possible,will be disposed of at the South Balloon GWTP.The presence of solids in liquid IDW generated during drilling and well development Ahtna Environmental,Inc. 17