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r • 23 June 2000 AGE-NC Project No 98-0511 Page 6 of 8 4 2 MONITORING WELL INSTALLATION PROCEDURES Monitoring well pilot borings will be advanced using hollow-stem auger drilling techniques Relatively undisturbed soil samples will be collected at five-foot Intervals in each of the bonngs using a California modified split-spoon sampler fitted with 2-inch diameter, 6-mch long brass sleeves Soil sample handling will be consistent with the procedures presented in Section 4 1 Following completion of drilling the boring, a 2-inch diameter Schedule 40 PVC 0 010-mch slotted well screen and casing will be installed Twenty feet of screen will be installed in each well, extending approximately 15 feet below and five feet above the top of the ground water table The well 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 potential for grout penetration into the screened section of the well The bentonite seal will be formed by pouring bentomte chips into the annular space between the auger 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 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 tremmie pipe The PHS-EHD will be notified for grout inspection at least 48-hours prior to conducting grouting procedures Following completion of the monitoring wells, well elevations and locations will be surveyed by a California-licensed surveyor 43 WELL DEVELOPMENT Development will consist of a combination of balling to remove the mayor 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 Advanced GeoEnvironmental,Inc