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Geosyntec" <br /> 4.2.2.2 Drilling <br /> The borings will be drilled by a C57-licensed drilling contractor using a mud-rotary drill rig. The <br /> boring will be logged by a field geologist under the direction of California Professional Geologist <br /> using the Unified Soil Classification System (USCS). In addition, geophysical logs will be <br /> collected from at least one boring at each pilot test location to compare against known geology <br /> from nearby monitoring wells. All downhole equipment will be decontaminated prior to use. <br /> The borings will be advanced until the top of the Corcoran Clay is encountered. Depth data from <br /> nearby borings installed during the ongoing supplemental characterization work will be used to <br /> guide drilling depth. The Corcoran Clay is anticipated to be encountered at depths between 260 <br /> and 280 feet bgs at each of the proposed locations. The boreholes will be reamed, as necessary, <br /> such that there will be at least 2 inches of annular space between the borehole wall and the outside <br /> of the well casing in accordance with the California Well Standards. <br /> 4.2.2.3 Well Installation and Development <br /> Biosparge and observation wells will be constructed with 2-inch inside diameter stainless steel <br /> casing and 0.010-slot stainless steel screen. The screen interval will be approximately 5 feet in <br /> length spanning the bottom of the transmissive well-graded sand and gravel layer immediately <br /> overlying the Corcoran Clay. Filter pack will consist of No.2-1/2 filter pack sand. Filter pack sand <br /> will extend approximately 2 feet above the top of the well screen and will be selected based on the <br /> geologic log and depth of the well. A bentonite seal, 3 to 5 feet in thickness, will be installed at <br /> the top of the filter pack. After the bentonite is hydrated, a Portland cement-grout seal will be <br /> tremmied into place in the annulus above the bentonite seal to the ground surface. Particular <br /> attention will be paid to well construction to ensure that short-circuiting of air along the annular <br /> space does not occur during biosparging. <br /> Well surface completions will be constructed with a traffic-rated vault or stovepipe completion <br /> with bollards depending on the well location and property owner's preference. The well will be <br /> fitted with a lockable sanitary sealing well cap.A conceptual well construction diagram is provided <br /> in Figure 5. <br /> After a minimum of 48 hours following well installation, the wells will be developed. <br /> Development will consist of a combination of bailing, surging, pumping, and air flotation. <br /> Groundwater quality parameters (temperature, pH, specific conductance, and turbidity) will be <br /> measured during purging activities. The well will be developed to remove the fine-grained <br /> materials and mud inside the filter pack and casing to stabilize the filter pack around the well <br /> screen and to produce representative water samples from the water-bearing zone. <br /> 4.2.2.4 Equipment Decontamination and Investigation-Derived Waste Management <br /> Prior to boring advancement, all drilling equipment will be cleaned thoroughly with a portable <br /> steam cleaning system supplied by the drilling subcontractor. <br /> In-Situ Bioremediation Pilot Test Work Plan—GSH Lathrop 9 <br />