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California Regional Water Quality Control Board <br /> Central Valley Reigon <br /> October 27 , 1989 <br /> Page #2 <br /> feet of perforated casing will extent above the existing <br /> static water level . The annular space between the perforated <br /> casing and the boring wall will be sand packed with Lapis <br /> Luster #lc sand (see Figure 3 ) to a level two feet above the <br /> top of the screened interval . A spacer will be placed above <br /> the sand pack to prevent infiltration of the grout seal into <br /> the sand pack. Silica flour, fine sand, bentonite pellets or <br /> crushed natural bentonite granules may be used for this <br /> purpose. This spacer will have a minimum thickness of one <br /> foot. The remaining annular space will then be filled with a <br /> cement/ bentonite grout. Bentonite is added to reduce <br /> shrinkage cracks in the grout seal . All depths and <br /> thicknesses of sand pack and seals will be verified by <br /> sounding with a weighted tape. All as-built construction <br /> details will be recorded and presented in the final report. <br /> Surface completions of all wells shall be below grade. <br /> The top of each well casing will be equipped with a PVC screw <br /> cap inside of a protective metal box. Each protective metal <br /> box will be fitted with a locking mechanism to guard against <br /> unauthorized tampering with the well . The surface elevation <br /> of each well will be determined to the nearest 0 . 01 foot by a <br /> certified land survey. <br /> 2) WELL DEVELOPMENT <br /> All wells will be developed to improve hydraulic <br /> continuity with the native soil. Development will be <br /> performed using pumping, bailing and/or surging of the well to <br /> a sand free state. The volume of all water extracted during <br /> development will be recorded along with regular pH and <br /> specific conductance measurements. Development will be <br /> continued until the well produces little or no fine sediment <br /> and pH and specific conductance readings have stabilized. <br /> 3 ) GROUND WATER SAMPLE COLLECTION <br /> Prior to the collection of ground water samples the depth to <br /> water in each well will be measured and recorded for use in <br /> determining the local ground water gradient. Each well will <br /> then be purged. Normal purging will consist of the removal of <br /> between three to five casing volumes of water. In the event <br /> of slow recovery, the well will be completely evacuated of one <br /> casing volume and the sample taken after recovery. Both <br /> purging and sampling will be performed using a Teflon bailer <br /> or Teflon/stainless steel bladder pump cleaned between wells <br /> with laboratory-grade detergent and triple rinsed with <br /> distilled water. <br /> Ground water samples will be taken from each well , placed <br /> in appropriate sample bottles, properly labeled, and placed in <br /> an iced cooler for transport to the laboratory. Chain-Of- <br /> Custody protocol will be maintained an all ground water <br />