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08 March 2000 . AGE-NC Project No 96-0232 Page 9 of 11 vapor using a photo-ionization detector(PID Thermo Environmental 580A, 10 0 eV, calibrated to isobutylene) and recorded on boring logs Soil sample duplicates will be described using the Unified Soil Classification System (USCS) and recorded on the boring logs Proposed soil boring locations are illustrated on Figure 2 Following borehole advancement,portland cement(grout mix)will be utilized to backfill each borehole utilizing a tremae pipe The PHS-EHD and the RWQCB will be given the opportunity to inspect the grout mix prior to backfilling activities 4 2 GROUND WATER MONITORING WELL PILOT BORINGS Pilot soil borings will be advanced utilizing a truck-mounted, hollow-stem drill ng and 8-inch diameter hollow-stem augers Cuttings generated during drilling activities will be placed on plastic sheeting and covered Rinseate will be containenzed in properly labeled DOT-approved 55-gallon drums, and stored on-site in an area lacking public access Disposal alternatives will be evaluated based on results of soil and water analysis 4 3 GROUND WATER MONITORING WELL COMPLETION Each group of"clustered" pilot borings will be single-completed as ground water monitoring wells utilizing 2-inch diameter schedule 40 polyvinylchlonde (PVC) 0 010-inch slotted well screen and blank well casing A 10-foot length of well screen is anticipated for installation of each "clustered" ground water monitoring well, however, based on geologic/hydrogeologic data collected from CPT soil borings, the well screen lengths may vary A proposed well construction diagram is depicted in Figure 3 After installing the well casing in each pilot bonng, a filter pack material consisting of pre-washed #212 Lonestar sand will be added through the augers over the screen interval 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 (pell plug-coded bentonite pellets) 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 pellets into the annulus and allowing them to settle on the filter pack The bentonite pellets 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 LU portland neat cement and not more than 6 gallons of water per 94- Advanced CeoEn-,ironmental,Inc