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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California 3.2.2 Well Development Well development will begin as soon as practicable after well construction but not sooner than 48 hours after construction is complete. If deemed necessary to remove mud or clay from the well to properly develop the well, non-phosphoric dispersants (such as Johnson Screen's Nuwell 220 dispersant polymer or equivalent) may be mixed at the surface, tremied into place, and allowed to activate per the manufacturer's recommendations. Any water and dispersant added during well construction will be removed before development. The development procedure will be accomplished by bailing and swabbing,followed by pumping.A sand bailer will initially remove fine-grained sediments and sand from the well. A surge block will gently swab the casing to increase flow from the formation into the well. Bailing and swabbing will continue until sediment is less than one teaspoon per bailer load before pumping begins. As necessary, an air isolation tool will then be used to remove water from the well via air displacement. The tool will be fitted with rubber diaphragms focusing on the water removal from 5-ft sections of the well screen. Well development with the air isolation tool will continue until the discharge water is visually absent of sediments. Water will be removed from the well using a submersible pump until field-measured water quality parameters have stabilized, or until at least ten well volumes are removed (DTSC, 2014). Groundwater parameters are considered stable when the following conditions are met after three successive measurements: • Plus/minus (±) 3.0 degrees Celsius (°C)temperature; minimum of±0.2°C • ±0.1 pH • ±3 percent (%) conductivity • ± 10 millivolts oxidation-reduction potential (ORP) • ± 10%dissolved oxygen • Less than 5 nephelometric turbidity units (DTSC, 2014; USEPA, 1986) 3.2.3 Aquifer Pumping Tests Aquifer pumping tests will be performed on each new extraction well to determine the optimum operational parameters.Aquifer pumping tests include a step-drawdown test followed by a constant-rate test. Step-drawdown tests will consist of pumping for one hour at 40 gallons per minute(gpm),then increasing the pumping rate by 20 gpm every hour until four steps are complete. Each well will be allowed to recover to within 10 percent of its initial water level before proceeding to the constant-rate test. During the step test, a sustainable pumping rate that optimizes drawdown while maintaining a steady water level in the well will be identified.This rate will be determined by manually reviewing the drawdown curves generated during the step test, calculating specific capacity, estimating the maximum pumping rate, and estimating aquifer transmissivity. Constant-rate tests will consist of pumping at a constant rate (identified by the results of the step- drawdown test) for a minimum of 12 hours and a maximum of 24 hours while collecting drawdown data from the extraction well and nearby wells.The length of the constant-rate test will depend on the aquifer's response. If water level measurements have been asymptotic for a sustained period (at least 2 hours) at any point after the 12-hour minimum, the constant-rate test may be terminated. For extraction wells Ahtna Environmental,Inc. 13