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_ GwSynte Consultants <br /> 4.2 Pilot Test Performa ce Monitoring Well Installations <br /> Two new performance monitoring wells will installed by a California licensed <br /> drilling subcontractor under supervision by GeoSyntec personnel. The total well depths <br /> and screened intervals proposed below will be subject to revision by GeoSyntec field <br /> personnel based on the subsurface conditions encountered. The wells will be installed <br /> using a hollow-stem auger (HSA) rig equipped with 10-inch nominal outer diameter <br /> augers. Soil samples will be collected for geologic description using a split-spoon <br /> sampler (SPT) at five foot intervals from the ground surface to 55 ft bgs. Continuous <br /> cores will be collected from 55 ft bgs to the bottom of the borehole. Geologic logs for <br /> each well boring will be prepared. <br /> The wells will be constructed of 4-in. nominal diameter, flush-threaded, schedule <br /> 40, polyvinyl chloride (PVC) casing, with 0.020-in. slot factory-cut well screen, and a <br /> flush-threaded bottom cap. The tops of the well casings will be fitted with <br /> expandable-gasket lockable caps. <br /> The total depths of the borings will be approximately 81 ft bgs, with the wells <br /> screened from approximately 60 to 80 ft bgs and a 6-in.-long bottom cap from 80 to <br /> 80.5 ft bgs. Prior to setting casing in each borehole, approximately 6 inches of sand will <br /> be tremied through the augers into the bottom of the boring. Once the casing and screen <br /> are set, filter pack will be tremied into the annular space surrounding the screen to a <br /> height of 3 ft above the top of the screen. An annular seal will be placed above the sand <br /> pack and will consist of approximately 3 ft. of bentonite chips hydrated with 5 gallons <br /> of water for a period of at least 30 minutes. Following placement of the annular seal, <br /> the remainder of the borehole will be filled with grout to 3 ft bgs. The surface <br /> completion of the wells will have flush mounted, traffic-rated 12-inch diameter well <br /> boxes cemented in place. <br /> Once installed, the wells will be allowed to recover for at least 48 hours prior to <br /> development. Well development will be performed under supervision of GeoSyntec <br /> l personnel and will serve to stabilize the filter pack and remove fines from the filter pack <br /> and well screen. Development will consist of a combination of bailing, surging, and <br /> pumping. Groundwater quality parameters (temperature, pH, specific conductance, and <br /> turbidity)will be measured during purging activities. <br /> �.I WC05038 Fiml.doc 11 7/21/2005 <br />