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1 24 September 1999 AGE-NC Project No. 96-0232 ' Page 9 of 12 ' water after washing with a solution of Alconox. All hollow stem augers will be steam-cleaned prior to advancement in each borehole. ' 4.1.2. MONITORING WELL COMPLETION ' The two pilot borings will be single-completed as ground water monitoring wells utilizing 2-inch diameter schedule 40 polyvinylchloride(PVC) 0.010-inch slotted well screen and blank well casing. Based on geologic/hydrogeologic conditions, a 20-foot length of well screen is anticipated for installation of monitoring wells; the bottom of the screen interval will be placed 15 feet below the water table. A proposed well construction diagram is depicted in Figure 3. After installing the well casing, filter pack material consisting of pre-washed #2/12 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 settling the filter pack. Additional sand 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 them to settle on the filter pack. Bentonite chips will be hydrated using approximately five gallons of tap water. The bentonite chips will be allowed to hydrate 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 1/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 tremmie pipe. A grouting inspection will be scheduled with PHS-EHD personnel. 4.1.3. WELL DEVELOPMENT ' Development of the proposed wells will consist of a combination of bailing with a stainless steel ' 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. Advanced GeoEnviron mental,Inc.