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Brown and iCaBt#a elel ' <br /> ConSdtants <br /> 723 S Street <br /> S=amenfo <br /> California 95814'7692 <br /> 1916♦444.0123 <br /> FAX(916)444-8437 <br /> April 11, 1990 <br /> Mr. Greg Lyon <br /> Environmental Health Division <br /> San Joaquin County, Public Health Services <br /> Post Office Box 2009 <br /> Stockton, California 95201 017-3214-52 <br /> Subject: Groundwater Extraction Well Design, ARCO Station 434, <br /> Lodi, California <br /> i <br /> Dear Mr. Lyon: <br /> i <br /> As you are aware, ARCO Products Company is planning to install numerous groundwater <br /> monitoring and vapor extraction wells at ARCO Products Company(ARCO)Station 434;n Lodi, <br /> California, during the week of April 16, 1990. In conjunction with this work, ARCO will be <br /> installing one groundwater extraction well on the site. This letter describes the design of that <br /> extraction well <br /> f <br /> j The well borehole will be drilled using a hollow-stem auger drilling rig. One soil sample will <br /> be collected from the saturated zone. This sample will be analyzed for grain-size using a sieve <br /> analysis to determine the appropriate screen size and filter pack material for the well. The screen <br /> and filter pack will be selected to maximize well production and minimize sediment influx. No <br /> other soil samples will be collected since the existing three wells in the immediate area have <br /> provided thorough definition of the degree of soil contamination, lithology, and depth to <br /> groundwater in the area. <br /> The borehole will be reamed to the total depth using a 12-inch-diameter auger, The screened <br /> interval will extend 20 feet into the saturated zone. A 5-foot sump will be planed on the bottom <br /> of the well to provide a sediment trap and additional depth for the extraction pumps. Water-level <br /> data collected in March 1990 indicated that the depth to water was 57 feet. Therefore, the total <br /> well depth will be approximately 85 feet below ground surface, with a 5-foot-long sump. The <br /> well will be constructed of Schedule 40 polyvinyl chloride (PVC) screen and blank casing,with <br /> a fitted PVC bottom plug. The filter pack will be installed to 2 feet above the top of the well <br /> screen. A 2-foot bentonite seal will be placed above the filter pack. The well will be grouted <br /> with bentonite-cement slurry or neat cement from the top of the bentonite seal to the surface. <br /> ' At the surface,the well will be completed with a water-:fight,flush-mounted,traffic-rated - <br /> 1 bo-x. The well construction details are shown on Figure 1. The well is designedfar two pumps: <br /> j a total-fluids pump and a skimmer pump. <br /> j <br /> .. - ...: <br />