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1�1 . T 15 April 2003 AGE-NC Project No. 02-0950 Page 8of10 V The well casing,filter pack and sealing materials will be placed into the borehole through the interior of the augers. After installing the well casing, filter pack material consisting of pre-washed silica 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 settling the filter pack. Additional sand will be added if settling occurs. A nominal two-foot thick bentonite seal will be placed above the filter pack to minimize the potential for grout penetration into the screened section of the well. The bentonite seal will be formed by pouring bentonite chips into the annular space between the hammer casing and the well casing 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 for a minimum of one-half hour prior to grouting. The remaining annular space above the bentonite seal will be filled to within one foot of 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 tremie pipe. The EHD will be notified for grout inspection at least 72 hours prior to conducting grouting procedures.A traffic-rated well box will then be installed over the well casing. A monitoring well diagram is illustrated on Figure 3. V 4.4. WELL DEVELOPMENT AND SURVEY V Development will consist of a combination of bailing to remove the major portion of fine-grained sediment from inside the well, surging to flush out or draw in sediment from the filter pack, and additional bailing to finish the removal of sediment.Development activities will be continued until field parameter(pH,electrical conductivity,and temperature)readings have stabilized.Additionally, each well head elevation will be surveyed by a licensed surveyor. -r 4.5. GROUND WATER SAMPLING PROCEDURES Ground water sample collection will be performed in accordance with CRWQCB guidelines (Tri- Regional Water Quality Control Board Recommendations for Preliminary Investigations and Evaluation of Underground Storage Tanks) sampling protocols. r Advanced GeoEnvironmental,Inc. v