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Z I <br /> l <br /> investigation. Well,MW-5 will be installed in this area and constructed as a 2-inch diameter. <br /> groundwater monitoring well. The well is not expected to exceed 60 feet in total depth and will <br /> be screened appropriately based on subsurface conditions identified during drilling. <br /> 4.3.1 Drilling and Soil Sampling <br /> Drilling will be performed by a C57-licensed-contractor using a truck-mounted rig equipped <br /> with 8-inch diameter hollow-stem continuous=flight augers (for the 2-inch diameter well) and , <br /> 10-inch diameter augers (for the 4-inch diameter well). All drilling equipment and sampling <br /> tools will be decontaminated prior to beginning the field activities. Reusable sampling <br /> equipment will be washed with a Liqui-Nox solution, rinsed with tapwater, and rinsed with <br /> distilled water prior to each use. An ETIC geologist will supervise the drilling and sampling <br /> activities. ' Soil samples will be examined for lithologic identification in accordance with the <br /> j Unified Soil Classification System and the Standard Practice for Description and Identification <br /> of Soils (Visual-Manual Procedure), American Society for Testing and Materials (ASTM) <br /> Designation D2488 (ASTM 2000), visible signs of contamination, and observations, Aill'be <br /> recorded on a field log. A field meter:will be used to monitor for organic vapors and to <br /> t measure headspace vapors from soil samples Technical guidance for the activities will be <br /> provided by a California Professional Geologist. <br /> At a minimum, soil samples will be collected at 5400t intervals for lithologic identification and <br /> laboratory,analyses. The samples will be collected in clean liners. The liners will be sealed, <br /> labeled, stored on ice in a thermally-insulated cooler, then transported and delivered to a state= <br /> certified analytical laboratory under chain.of custody protocol. If evidence of contamination <br /> exists, then additional soil samples may be collected and submitted for laboratory analyses. <br /> l The soil samples will be analyzed for,TPH-g, BTEX, MTBE, and TBA by EPA Method . <br /> f 8260B. One soil sample will be collected from the silt at approximate 30 to 35 feet and one soil <br /> sample will be collected from the saturated sand at approximately 47.feet from well MW-2A <br /> for analysis of permeability and bulk density.. <br /> 1 4.3.2` Groundwater Monitoring Well Construction <br /> Final well`'construction details, including the slot=size used in the screened portion of each well <br /> will be determined based upon hydrogeologic data;obtained during drilling. However; we <br /> I anticipate+using 0.010-inch factory-slotted Schedule 40 polyvinyl chloride (PVC) casing. An <br /> appropriately-sized filter pack (likely Lonestar 42/16 or #2/12 sand) will be placed in the <br /> iannular space of the borehole adjacent to the screened interval. The filter pack will be <br /> extended slightly above the top of the screened interval (approximately 1 foot) to allow for <br /> settlement during well development.. A 2-foot;thick transitional seal, consisting of hydrated <br /> bentonite, Will be placed above the filter pack in the annular space of the borehole. A grout <br /> l' slurry, consisting of neat cement,'will be placed in the annular space above.the bentonite seal to . <br /> l <br /> SL-Cwta-SCM and Rm RI WP 2007.09 - 16 <br />