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. 14-September 1998 AGE-NC Project No. 98-0468 Page 8 of 10 has been encountered, a hydropunch-equivalent water sampling device twill be driven two to three feet into the water bearingzone, Grab ground water samples will be collected from.the hydropunch- equivalent water sampling assembly or a pre-cleaned one-inch diameter 0.010-inch slotted temporary. well screen. Each ground water sample will'be extracted by lowering a Teflon bailer through the hollow center of the push rods into the screen section or by retrieving the hydropunch assembly.' Samples will be collected in laboratory-supplied sample,containers as described in Section 4.5.4.The. labeled vials will be placed in a chilled container under ice and transported under chain-of-custody to a DTSC-certified laboratory. 4.3. MONITORING WELL'INSTALLATION The.monitoring well borings will be completed using hollow-stem auger drilling techniques. Following completion of drilling the boring; a 2-inch diameter Schedule 40 PV %'0.410-inch slotted r well screen and casing-will be installed. A 15-foot section of well screen will installed in'each ' well, extending approximately I 0 feet below and five feet above the top of the ground water table. The casin 'filter pack and sealing materials will•be. laced into the borehole through the interior of g� P g p g the hollow-stem augers. After installing the well casing,filter pack material consisting of pre-washed 42/12 Lonestar,sand will be added from the bottom of the borehole to approximately two feet above the,screened interval. Following placement of the filter pack, the well will be'surged'to assist'in Ste' settling the filter pack. Additional sand will be added. if'settling occurs. An approximately two foot bentonite seal will be placed above the'filter pack to minimize the potential of grout penetration into the screened section of the well. The bentonite seal will be formed by'pouring bentonite chips into the annulus and allowing them to settle on the filter pack. Bentonite. chips will be hydrated using.five gallons of water. The bentonite chips will-be'allowed to hydrate fora minimum of ons e-half hour' for to grouting. The remaining annular space will be filled to the ground surface with a cement-grout. The grout mixture'will consist of Type I/II portland neat cement and not•more than 6 gallons of water per 94- pound sack of cement. The'grout will be placed,by pumping through trelrlmie ine. Grouting , procedures will be inspected by PHS-EHD'personnel. T Following completion of the monitoring wells, well elevations and locations will be surveyed by a California-licensed surveyor. Advanced GeoEnvironmental,Inc.