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12 February 1999 AGE-NC Project No. 98-0540 Page 6 of 8 Following completion of hollow-stem auger drilling activities, a PVC two-inch diameter Schedule 40, slotted well screen (0.020-inch) and well casing will be installed. The casing, filter pack and sealing materials will be placed into the borehole through the interior of the hollow-stem augers.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 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 for a minimum of,one-half hdur prior to inserting the second well casing. The same installation procedures will apply for both the deep screened interval and the shallow screened interval. Following hydration of bentonite chips, the remaining annular space will be filled to the ground surface with a cement grout. The grout mixture will consist of Type UII 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. Proposed well construction diagrams are illustrated in Figures 3 and 4. Grouting procedures will be inspected by PHS-EHD personnel. Following completion of the monitoring wells, well elevations and locations will be surveyed by a California-licensed surveyor. 4.3. WELL DEVELOPMENT Development will consist of a combination of bailing and ground water pumping to remove the major portion of fine-grained sediment from inside the well and surging to flush out or draw in sediment from the filter pack. Development activities will be continued until field parameter(pH, electrical conductivity, and temperature) readings have stabilized. 4.4. GROUNDWATER SAMPLING PROCEDURES Groundwater sample collection will be performed in accordance with pertinent applicable sampling protocols, details of which are presented below. Advanced GeoEnvironmental,Inc.