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s <br /> Monitoring-Well Construction <br /> Monitoring wells will be used to evaluate the groundwater flow direction and whether <br /> d <br /> hydrocarbons are present in the ground water near suspected sources of hydrocarbons and <br /> at the margins of the site. Monitoring wells will be constructed in the bsing.s with thread- <br /> at chemical) <br /> jointed, 4-inch-inner-diameter, Schedule 40 polyvinyl chloride (PVC) casing. <br /> cements,glues, or solvents will be used in well construction. The screened portion of each <br /> well will consist of facto ry-perforate°d sing with 0.020-inch-wide slots. The well screen will <br /> extend from the total depth of the well to approximately 3 feet above the groundwater <br /> surface. This screened interval will allow sampling at the air-water interface during seasonal <br /> fluctuations of the groundwater level. The annular space in the well will be packed with <br /> number 3 sand to approximately 1 to 2 feet above the slotted interval, A 3-foot thick <br /> bentonite plug will be added above the sand pack to prevent the cement from entering the <br /> well pack. The remaining annulus will be backftll::d to grade with a bentonite cement <br /> slurry. Well construction details are presented in the attached Schematic Well Design. <br /> Monitoring wells will be protected with a traffic-rated, cast-aluminum t utility box equipped <br /> with a PVC skirt. The box has a watertight seal to protect against surface-water.infiltration <br /> and must be opened with a special wrench. The design of this box discourages vandalism <br /> and reduces the possibility or accidental disturbance of the well. <br /> i Well Develo ment <br /> c <br /> RESNA Industries will wait a minimum of 24 hours after well instal,ation before developing <br /> `J the groundwater monitoring wells to allow the grout to seal. Before. developing the <br /> monitoring wells, a water sample will be.collected for subjective analysis ft'Lm ne:r the <br /> water surface in the well with a Teflon bailer cleaned with a laboratory-grade detergent and <br /> deionized water. If floating product is encountered in the %yell, the thickness of the product <br /> will be measured with an interface probe and recorded and the water will not be sampled <br /> for chemical analysis. Product will be bailed from the well and stored in appropriately <br /> j labeled drums onsite. RESNA Industries will evaluate the disposal optionsand apprise <br /> ARCO of these options: <br /> If no floating product is detected,the wells will be developed with a surge Itlo_k and pump. <br /> ue until the discharge water is clear of silt and sand. Clay <br /> Well development will cont -size <br /> in <br /> F sediments derived from the screened portion of the formation cannot'o entirely eliminated. <br /> by wall development.. <br /> ize for a minimum of.! hours, the well will be <br /> After the well has been allowed to stabil <br /> - purged of stagnant water and a sample will be collected for laboratory analysis. The well <br /> ately 3 to well volumes of water with a submersible pump, or <br /> will be purged of approxim <br /> until Fh, conductivity, and temperature of the purged water have stabilized. Water purged <br /> ~— ---- - ---" from the t++ells will be stored in labeled.55-gallon,-steel drums-approved for this use by the <br /> 30D03-4%V , <br /> t�E <br /> S <br />