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ff <br /> September 13, 1991 <br /> Unocal Siation No. 6981, Siockton, California <br /> The screened interval should allow sampling at the air-water interface during seasanal <br /> fluctuations of the ground-water level, unless confined groundwater conditions are <br /> encountered. <br /> If confined ground-water conditions are encountered, the top of the screen interval will be <br /> placed at the top of the water-bearing zone. "f1ie annular space in the well will be packed <br /> with 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. 'Ilse remaining annulus will be backfilled to grade with a bentonite cement <br /> slurry. Well construction details are presented in the Schematic Well Design(Appendix Q. <br /> Monitoring wells will be protected with a traffic-rated, cast-aluminum 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 possibil4y of accidental disturbance of the well. <br /> RESNA will wait a minimum of 24 hours after well installation before development of the <br /> ground-water monitoring wells to allow the grout to seal. Before development of the <br /> monitoring wells, a water sample will be collected for subjective analysis from near 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 well, 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 /> labeled drums onsite. RESNA will evaluate the disposal options and apprise Unocal of <br /> these options. <br /> - - 38032-AW---- 13 <br /> hr <br />