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a <br /> y 4 <br /> 13 November 2000 <br /> AGE-NC Project No. 98-0481 <br /> Page 8 of 10 <br /> 4.2. GRAB GROUND WATER SAMPLING PROCEDURES <br /> Grab ground water sampling procedures are outlined in the AGE-prepared, Additional Site <br /> Assessment Work Plan dated 22 February 2000 and approved by PHS-EHD. <br /> L.0 <br /> 4.3. MONITORING WELL INSTALLATION PROCEDURES <br /> Proposed monitoring well pilot borings will be completed using hollow-stem auger drilling <br /> ,y techniques. Relatively undisturbed soil samples will be collected ahead of the drill bit at five-foot <br /> intervals in each of the borings using a California modified split-spoon sampler fitted with 2-inch <br /> diameter, 6-inch long brass sleeves. Soil sample handling will be consistent with the procedures <br /> presented in Section 4.1. <br /> Following completion of drilling the pilot boring, a 2-inch diameter Schedule 40 PVC 0.010-inch <br /> i.y slotted well screen and casing will be installed. A 20-foot section of well screen will be installed <br /> in each well, extending approximately 15 feet below and five feet above the top of the ground water <br /> table. <br /> The well casing,filter pack and sealing materials will be placed into the borehole through the interior <br /> of the hollow-stem augers. After installing the well casing, filter pack material consisting of pre- <br /> washed #2/12 Lonestar sand will be added through the augers to the bottom of the borehole to <br /> r approximately two feet above the screened interval. Following;placement of the filter pack,the well <br /> will be surged to assist in settling the filter pack. Additional sand will be added if settling occurs. <br /> A nominal two-foot thick bentonite seal will be placed above the filter pack to minimize the potential _ <br /> of grout penetration into the. screened section of the well. The bentonite seal will be formed by <br /> pouring bentonite chips into the annular space between the auger and the well casing and allowing <br /> them to settle on the filter pack. Bentonite chips will be hydrated using five gallons of water. The <br /> �. bentonite chips will be allowed to hydrate for aL minimum of one-half hour prior to grouting. <br /> The remaining annular space above the bentonite seal will be filled to within one foot of the ground <br /> surface with a cement grout. The grout mixture will consist of Type VH portland neat cement and <br /> not more than 6 gallons of water per 94-pound sack of cement. The grout will be placed by pumping. <br /> through tremie pipe. The PHS-EHD will be notified for grout'inspection at least 48-hours prior to <br /> conducting grouting procedures. <br /> Following completion of the monitoring wells, well elevations,and locations will be surveyed by a <br /> California-licensed surveyor. <br /> .Lao, <br /> Advanced GeoEnvironmental,Inc. <br /> cr <br />