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e _.w _ it 9 greater than 50 feet. Borehole cuttings will be stored in 55-gallon barrels. The disposal of these cuttings is the responsibility of GLDM. Boreholes will be destroyed immediately after drilling by grouting with a bentonite-cement grout mixture placed by tremie pipe. Soil Sampling. Continuous soil cores for lithologic classification will be collected from all boreholes to the total depth of the borehole, using a 5-foot-long, split-sampling barrel inside the auger. Samples for laboratory analysis will be collected using a 1.5-foot-long, split-spoon drive sampler, lined with three 2-inch-diameter brass liners. The sampler will be driven into undisturbed soil ahead of the augers. The lithology of each borehole will be described according to the Unified Soil Classi- fication System. The boreholes will be logged by an experienced field geologist working under the direct supervision of a registered geologist. Observations of visible hydrocarbons and hydrocarbon odors will also be noted. The soil samples w_ii be screened on site with a portable vapor meter to detect hydrocarbon vapors. These data will be recorded on the Iog. Soil samples will be collected for laboratory analysis at 10-foot intervals. The sample analyzed will be that sample having the highest detected vapor reading in that 10-foot interval. Brass liners containing soil samples selected for laboratory analysis will be covered with aluminum foil and plastic caps and sealed with plastic tape. Each sample will be labeled on site to show the date, project number, sample Iocation,and depth interval. The sealed samples will be stored on ice in closed chests and protected from meltwater. Selected soil samples will be analyzed for BTX and TPH by U.S. Environmental Protection Agency (EPA) Method 8015, modified, Extraction Method 5430. The samples will be delivered to Brown and Caldwell Analytical Laboratories, Inc. (BCAL), in Emeryville. Well Redevelopment and Sampling Monitoring wells MW-1, MW-2, MW-3, MW-4, and MW-5 will be redeveloped by "vacuuming" sediment from the well using a diaphragm pump. After vacuuming each well, they will be surged using a stainless steel bailer. The wells will then be pumped again to remove any additional sediment dislodged by the surging process. The wells will be allowed to recover f!_-1!y prior to sampling. Water and sediment produced during well redevelopment and sampling will be contained in 55-gallon barrels. GLDM will be responsible for disposal of water, sediment and any recovered petroleum product. Prior to and following redevelopment, the depth to water will be measured using an oil/water interface probe. Groundwater Sampling. Prior to sample collection, at least three well volumes of groundwater will be removed. A well volume is defined as the amount of groundwater in the well casing and the sand pack with an assumed porosity of 35 percent. The pH and electrical conductivity of the water will be measured periodically prior to sample collection. Groundwater samples will be obtained with a teflon bailer. Sample bottles will be filled to the brim directly from the bottom-emptying valve of the bailer. A teflon-lined cap will be placed on the bottles, and the bottles will be checked to determine that no air bubbles remain within.