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i <br /> 3 <br /> Groundwater Monitoring Wells <br /> ,s During monitoring well installation, the following procedures <br /> will be used. These methods will ensure the proper identification of <br /> groundwater quality beneath the site. <br /> } Groundwater Monitoring VI -11 Installation. Three groundwater <br /> monitoring wells will be installed in the boreholes shown on <br /> 3 Figure 1. <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 20 feet below the groundwater surface ' ^' <br /> {' : "ta" 10 'feet-'above:the= groundwater ;surface.... Blank casing will <br /> from the top of the perforated section to--­ground ,surface. The actual <br /> depths of the boreholes and screened 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 1. <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 she top of the bentonite seal to the surface. The <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 /> i clay zones nor will monitoring wells penetrate significant clay zones <br /> that might allow for downward migration of contamination into lower <br /> aquifers. <br /> r <br /> rte, Well Develo ment and Groundwater Samples. Each .well installed • ,y <br /> r <br /> `z will be developed with an air-lift pump until clean, sediment-free F) <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, <br /> will be gauged. • <br /> �rS <br /> -� Following proper development . of each well, a nitrogen-driven <br /> bladder pump or stainless steel bailer will be used to evacuate 'an <br /> �. additional amount of water before samples are taken. The amount of si <br /> water evacuated will be defi-ned by—the -staoilizatior_of pH--and - ---- <br /> r <br /> electrcial conductivity readings for three .consecutive measurements <br /> taken 5 .minutes apart. When pH and electrical conductivity have been <br /> determined to have stabilized, water samples will be collected and <br /> submitted to the .laboratory to be analyzed for BTX (EPA 602) , and <br /> total petroleum fuel hydrocarbons (modified EPA 8015) .. Sample <br /> k <br /> 4 <br /> 4 <br /> r - <br />