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No. 2/12 sand or equivalent that extends at least three feet above the top of the screen. A five-foot thick medium -chip bentonite seal will be placed above the filter pack. The remaining annular space will remain open. A disposable bailer will be lowered through the well casing to extract the groundwater sample for analysis of VOCs. Sample collection methods are described in more detail in Section 3.4.6. The temporary well will remain in the borehole for up to two weeks to allow water levels to stabilize. After the temporary well is sampled, the top of the well will be secured by placing approximately two inches of chipped bentonite around the perimeter of the borehole opening and then placing a steel plate over the borehole and on top of the ring of benonite chips. The steel plate and bentonite chips will be placed in such a manner to prevent surface water from entering the borehole. Additional bentonite and/or native soils will be placed around the steel plate to divert surface water away from the borehole mouth. If VOCs are detected in the temporary well sample, the casing will be removed, and the borehole will be abandoned, and a replacement "step -out" borehole and temporary well will be drilled and constructed according to the procedures outlined above. Borehole abandonment will be conducted by removing the well casing, reaming out the filter pack sand, and backfilling the borehole with a neat cement grout mixed at a ratio of one 47 - pound bag of Type II/V Portland cement for every 6 gallons of water. All abandonment activities will be conducted in accordance with County of San Joaquin Environmental Health Department guidelines. After the grout has settled, the ground surface will be restored to original grade using hand tools and surrounding soils to minimize depressions in the ground surface. ® 3.4 MONITORING WELL INSTALLATION Permanent monitoring wells will be constructed when the results of the VOC analyses from the temporary well samples indicate non-detectable concentrations. 3.4.1 Borehole Reaming and Soil Sampling At each site where the temporary sample indicates non-detectable VOC concentrations, the temporary well casing will be removed, and the borehole will be reamed in preparation for well construction. Boreholes will be reamed to 10 inches using hollow -stem auger methods. Once the ream advances to the original depth of the exploratory borehole, drilling will continue up to 20 feet, and soil samples will be collected continuously using split -spoon sampling and logging methods described above. All drilling operations will be continuously observed, and samples will be retained for geologic logging purposes. 9 2011-0115 CHSL EMP Workplan Geo -Logic Associates Revision 2 —January 11, 2012