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kJ <br /> Technical Approach <br /> The work plan will include construction of one groundwater monitoring well; with <br /> the monitoring well being within 20 feet (or as close a safely practicable of the <br /> former tank location) on the surmised down gradient side. Soil and groundwater <br /> samples will be analyzed for Total Petroleum Hydrocarbons as Gasoline (TPHG), <br /> Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) . These compounds should cover <br /> the contaminants of interest to the PHS-EHD <br /> Scope of WQ <br /> Exploratory Soil Borings and Monitoring Well Installation Procedures <br /> One exploratory boring will be drilled with truck mounted hollow-stem auger, which <br /> - -_ <br /> has-been cleaned=prior to use: The well twill-be-installed under approved permits-of <br /> the PHS-EHD. The boring will be advanced to the uppermost water bearing stratum, <br /> and advanced ten feet into the aquifer and terminated in the aquitard underlying <br /> that stratum or 125 feet, which ever is less. Construction of wells is expected to <br /> require boring greater than 100 feet deep to encounter water. A geologist will log <br /> the boreholes by collecting samples at 5-foot intervals, lithologic contacts of interest <br /> and areas of obvious contamination, using the Unified Soil Classification System. For <br /> the purposes of this investigation, 25 soil samples will be collected (above the water <br /> table) in precleaned brass liners contained in a split spoon sampler driven ahead of <br /> the drill bit. Soil samples collected for chemical analysis will be removed, sealed with <br /> foil and endcaps, labeled, logged onto chain-of custody forms and packed on ice for <br /> transport to a State certified laboratory for analysis. The sampler will be <br /> decontaminated prior to the next drive. Drill cuttings will be stored on site, between <br /> plastic for characterization a later date. Wright will dispose of the drill cuttings <br /> subsequent to laboratory results. <br /> The monitoring well will be constructed using precleaned, threaded 4-inch diameter <br /> Sch. 40 PVC well casing, screening the entire thickness of the aquifer, and a portion <br /> above the capillary fringe to allow observation for possible floating product. Glues <br /> will not be used to construct well casing. Final well design will depend upon <br /> subsurface conditions encountered. The annulus between the casing and the <br /> borehole will be backfilled with 2/12 sand to about two feet above the screens. A <br /> bentonite clay spacer about two feet thick will be placed above the sand pack, and <br /> cement grout will be pumped from above the bentonite to the surface using a tremae <br /> - --�-- <br /> pipe.—A,.traffic rated access,vault-box-with-locking,device will cap the wellCasings—-r <br /> will be measured for elevation to a known reference datum. <br /> Monitoring Well Development and Sampling Procedures <br /> The well will be developed prior to sampling by surge and bailing to remove the <br /> drilling muck and borehole "smear" to improve hydraulic contact. Completeness of <br /> development will be made on the clarity of water, amount of sand and silt entry based <br /> upon well performance and field judgement. A well development log will be kept. <br /> Sampling procedures will follow after a minimum of 24 hours. The well will be <br /> sampled by first sounding the well with an electronic probe to measure depth to <br /> water and check for.p'resence of floating product. If product is encountered, a bailer <br /> will be used to check and measure the apparent thickness. Following this, the purge <br /> volume will be calculated and removed to allow aquifer water to enter the well. The <br />