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California Regional Water Quality Control Board-Central Valley Region 23 February 2022 Page 3 PVC casing will be installed below the well screen as a silt sump to collect particulates that may settle in the well. • Injection wells IW-1 and IW-2 will be constructed of six-inch diameter,Schedule 80 PVC,with up to 100 feet of six-inch diameter, stainless steel,wire-wrapped screen (with 0.030-inch slot size). The target screen interval is approximately 50 to 150 feet bgs,which corresponds to the A and C1 Zones of the Upper and Intermediate Aquifers, respectively.A four-feet-long section of PVC casing will be installed below the well screen as silt sump. • Note that the screen intervals above are estimated;the actual screen intervals will be determined in the field based on the subsurface lithology encountered. After construction, each well will be set inside the drill casing to total depth,with centralizers placed approximately every 20 feet to keep the well centered in the borehole. Annular materials will then be placed while incrementally retracting the drill casing.The annular space around the well will be backfilled with#3 filter sand (or equivalent)from the bottom of the well to approximately three feet above the top of the screen interval,followed by an additional two feet of finer-grained transition sand. A two-feet thick transition seal of hydrated bentonite chips will be placed above the filter and transition sands. A sanitary seal of neat cement grout will then be placed (in two lifts,to mitigate thermal deformation of the PVC casing)from the top of the bentonite to bus elow ground surface.The extraction well will be completed with an above ground locking stove-pipe monument and the injection wells will be completed in below grade utility vaults. Proposed construction details for the extraction and injection wells are shown in Figures 3 and 4, respectively. WELL DEVELOPMENT AND SURVEY METHODS A minimum of 48 hours after installation,each well will be developed using surge-and-purge methods. The screen interval of the well will first be surged with a surge block; a bailer will be used to remove any accumulated sediment at the bottom of the well after surging.The well will then be purged until groundwater field parameters (turbidity, pH,temperature,and specific conductance) stabilize.The pumping rate and drawdown will be recorded during development to estimate the specific capacity. Haley&Aldrich will contract with a California-licensed surveying company to survey the horizontal location and vertical elevation of the top of each well casing as well as ground surface elevations adjacent to the wells. The horizontal location will be surveyed relative to the North American Datum of 1983,and the elevation will be surveyed relative to the North American Vertical Datum of 1988. DECONTAMINATION AND WASTE MANAGEMENT All re-used down-hole equipment(such as drill casing)will be decontaminated using a pressure washer or steam cleaner. Soil cuttings and decontamination/development water will be containerized separately pending profiling and disposal at an appropriate facility. RICH