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. 3 <br /> Groundwater Monitoring Wells <br /> 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 Well Installation. Three groundwater <br /> monitoring wells will be installed in the boreholes shown on <br /> Figure 1, <br /> The wells will be completed with 2-inch--diameter polyvinyl <br /> chloride (PVC) flush-threaded casing and will be'. sc•-_ened with <br /> ..,,0.020-,inch slotted casing from 20 feet below the- groundwater surface <br /> to•,-1O feet �above,� the_:groundwater surface. Blank,.casing will:-e!itend ., <br /> from the top of the perforated section to -ground - surface. Thy 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 <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 to - of the <br /> sand pack. The wells will be grouted with bentonite--cement scurry or <br /> neat cement from the 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 /> clay sones nor will monitoring wells penetrate significant clay zones <br /> 1� that might allow for downward migration of contamination into lower <br /> Y aquifers. f <br /> Well Development and Groundwater Sample Each well installed <br /> will .be developed with an air-lift pump until clean, sediment-free <br /> _:water isproduced from the well. The length of development time = <br /> ,rill 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 S, <br /> to.:and following development, the thickness of Free product, if any, ry <br /> wily be gauged. . <br /> Following proper development of each well, nitrogen--driven <br /> bladder pump or stainless steel bailer will be used to evacuate an u <br /> additional amount of water before samples are taken. The amount of <br /> water . evacuated _ will--be defined--by- the-stabilization- of -pH---and s- <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 /> ti-tal petroleum fuel hydrocarbons (modified . EPA 8015) . Sample <br />