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�N5Cfip'� lots o � s a1� d We- t1, -S+0- � { <br /> O <br /> Task 3 Drilling and Soil Sampling <br /> Completion of this task includes the installation of 2 ground-water <br /> monitoring wells and 6 additional soil borings. Drilling locations are those <br /> shown in the Subsurface Investigation Plan revision. Boreholes will be <br /> drilled using continuous flight hollow-stem auger drilling equipment. Soil <br /> samples will be collected at 5-foot intervals by advancing a California <br /> modified split-spoon sampler, equipped with brass liners, 18 inches into <br /> the soil beyond the tip of the augers. Soil samples will be logged by an <br /> EMCON geologist working under the supervision of a California registered <br /> geologist. <br /> The soil samples will be inspected for evidence of petroleum hydrocarbons <br /> by noting visible product, product odor, or volatile hydrocarbon vapors as <br /> detected by a field photoionization detector (PID). Based on the results of <br /> these tests, appropriate samples, as identified in the Subsurface <br /> Investigation Plan, will be selected for chemical analysis. Samples <br /> selected for chemical analysis will be retained in the brass rings, sealed <br /> with Teflon@ tape and polypropylene end caps, and transported to the <br /> analytical laboratory in a cooled shuttle under chain-of-custody. The <br /> Subsurface Investigation Plan recommends collection of background <br /> samples. EMCON would recommend deletion of background sampling as <br /> background levels should be below detection limits. EMCON <br /> recommends the collection and analysis of a duplicate soil sample to <br /> provide quality assurance (QA) data. <br /> Monitoring wells will be constructed of 2-inch diameter, schedule 40, flush <br /> threaded polyvinyl chloride well casing. Fifteen feet of slotted casing will <br /> be placed so that 5 feet extends above the expected water table. <br /> Appropriately sized sand pack will be placed around the screen. A <br /> bentonite seal will be placed on top of the sand pack. The remaining <br /> annular space will be sealed with a cement grout containing 5 percent <br /> bentonite. If necessary, wells will be constructed below grade so as not to <br /> interfere with current site operations. Access to the wells will be by way of <br /> a christy box placed slightly above ground level. The top of the wells will <br /> be sealed with a water-tight cap to prevent surface water entry and locked <br /> to restrict access. Borings not completed as wells will be abandoned by <br /> grouting of the annular space. <br /> Task 4 Monitoring Well Development and Ground-Water Sampling <br /> Following installation of the monitoring wells, development will occur by <br /> bailing, surging, or other appropriate technique. Development will <br /> continue until representative ground-water samples can be obtained. <br /> - I ­^^ .1 November 13, 1990 <br />