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T <br /> 3 <br /> Gr <br /> Method 8020) , and total petroleum" fuel hydrocarbons (EPA .8015) . The <br /> samples will be delivered to BC's° analytical Zaboratory in Emeryville <br /> within 48 hours of collection. <br /> Groundwater Monitoring Wells <br /> During monitoring well installation, the following procedures <br /> will be used. These methods will .sensure the proper identification of <br /> groundwater quality beneath the site. <br /> Groundwater _ Monitoring Well Investigation. Four groundwater <br /> monitoring wells will be installed in the boreholes shown on J <br /> Figure 1. A total of three _groundwater monitoring wells is required <br /> to determine groundwater gradient .and flow direction. <br /> The wells will be completed with 2--inch-diameter polyvinyl <br /> chloride (PVC) flush-threaded casing and will be screened with <br /> 0. 020-inch slotted casing from 10" feet below the groundwater surface <br /> to 10 feet above the groundwater ; surface. Blank casing �will. extend . <br /> from the top of the perforated section :to ground surface. The actual <br /> depths of the boreholes and scr-eened intervals of the wells will <br /> depend on conditions encountered during drilling. <br /> The wells will be packed with No. 20/40 sand from the bottom of <br /> the screen to approximately 2 feet above the top of the° screen. A <br /> 2-foot seal of bentonite pellets will be placed on the top of the <br /> sand pack. The wells will be grouted with bentonite-cement ;.slurry or <br /> neat cement from the top of the bentonite seal to the surface. The i <br /> wells will be completed below grade, :fitted with top and bottom PVC <br /> caps, and have locking covers installed . Typical well construction { <br /> is illustrated on Figure 2. <br /> The monitoring wells will not be completed opposite significant <br /> clay zones nor will monitoring wells penetrate- significant ,'clay zones <br /> that might allow_ for downward migration of contamination into lower <br /> aquifers. 1 <br /> Well Development and Groundwater Samples: Each well installed <br /> will be developed by surging and , pumping until clean, sediment-free ; <br /> water is produced from the well: The length of -development time <br /> will vary depending upon field conditions. Water produced during <br /> development and sampling will be contained on site. ARCO will be <br /> responsible for the disposal of water and product collected. Prior <br /> to and following development, the thickness of free product, if any, j <br /> I <br /> will be gauged. <br /> Following proper development of each well, a nitrogen-driven <br /> bladder pump or stainless steel bailer will be used toevacuate an <br /> additional amount of water before samples alre, taken. The amount of <br /> water evacuated : will be defined by the stabilization of pH and + <br /> electrical conductivity readings �'for three consecutive measurements <br /> i' <br /> r � <br />