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03/16/2001 11:33 20946710 AGE STOCKTON • PAGE 10 12 March 2001 AGE-NC Project No. 97-0333 Page 7 0£8 After installing the well casing in each boring,a filter pack material will be slowly emplaced through the augers over the screen interval to approximately two feet above the screened intervals; filter pack material in the ground water extraction well will consist of a 50/50 blend of pre-washed small- grained aquarium gravel and#3 Lonestar sand; filter pack material in the ground water observation well will consist of pre-washed 43 Lonestar sand. Following placement of the filter pack, the screened interval from each well will be surged for approximately 20 minutes utilizing a six-inch diameter surge block to assist in settling the filter pack.Additional filter pack material will be added if settling occurs. A nominal two-foot bentonite seal(bentonite chips)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 annulus and allowing the pellets to settle on the filter pack.The bentonite pellets will be allowed to hydrate with tap water for a minimum of one-half hour prior to grouting. The remaining annular space will be filled to the ground surface with a cement grout. The grout mixture will consist of Type IM 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 tremmic pipe. A grouting inspection will be scheduled with PHS-EHD personnel. 4.3. WELL DEVELOPMENT Development of the proposed extraction and observation wells will consist of a combination of bailing with a two- or four-inch diameter PVC bailer 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 ground water evacuation(purging)with a submersible pump to finish the removal of fine- grained sediment. Developmental purging activities will be continued until field parameter (pH, electrical conductivity, and temperature) readings have stabilized and purged water is visually sediment-free. 4.4. AQUIFER PUMP TEST A 12-hour aquifer pump test will be conducted at the site to induce a decline in static water level in the newly installed ground water extraction well (screened 15 to 35 feet bsg). Pressure transducers will be deployed in wells EW-1,MW-2,MW-3 and the newly installed observation well to measure difference in ground water levels before well pumping versus time during well pumping. A constant ground water pumping rate(approximately 4 gallons per minute)will be utilized from the ground water extraction well during the aquifer pump test to achieve optimum draw-down influence.Results of the draw-down pilot test will be included in a report of findings and submitted to the PHS-E.H.U. Advanced GeoEnvlronmental,Ina