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i 23 A composite soil sample will be collected from the drill cuttings of each borehole for soil disposal purposes. The procedure for composite soil sample handling and laboratory analysis will be the same as that described for the groundwater extraction well ;borehole composite soil sample. Construction of Monitoring Wells. Constru tion of wells will be completed with 30 feet of nominal 2-inch-diameter, polyvinyl chloride (PVC), 0.020-inch slotted flush- threaded casing. The slotted casing will extend a proximately 20 feet below the ground water surface and 10 feet above. This design will accommodate any seasonal groundwater level fluctuations that might occur at the site location. Blank casing will extend from the top of the perforated section to ground surface. PVC caps will be installed at the'. top and bottom of each well. Actual depths of the boreholes and screened intervals will depend on the conditions encountered during drilling. The wells will be packed with No_ 1%20 sand from the bottom of the screen to approximately 2 eet above the top of the screen. A 2- foot-thick layer of bentonite pellets will be placed on the top of the sand pack. The remaining annular space will be grouted with be tonite-cement slurry placed b`y tremie pipe. The wells will be completed at grade usingwater-tight locking covers. Typ cal well construction is illustrated on Figure 11. Well Development. Each well will be developed by surging, bailing, or yumping until clean, sediment-free water is produced from the well. The length of development time will vary depending upon field conditions. Water produced during developrnent and sampling will be contained in 55-gallon barrels. ARCO will be responsible�l for the disposal of water and any recovered petroleurn product. Prior to and following development, the depth to water will be measured mith an oil/water interface probe; Groundwater Sampling. Prior to sample co lection, at least three well volumes of groundwater will be removed. A well volume is fined as the amount of groundwater in the well casing and the sand pack with an assume porosity of 35 percent. The pH and electrical conductivity of the water will be measure periodically prior to sample collection. :i Groundwater samples will be obtained with a teflon bailer. Sample bottles will be filled to the brim directly from the bottom-emptyinj 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. All water samples will be labeled, stored, and transported as described iri' the soil sampling section above. The water samples will b submitted to Eureka Laboratones, Inc., for analysis of BTX by EPA Method 602. Well Surveying and Measurement of Water Level. Procedures for TOC surveying and measurement of water levels will be the same as those described for the groundwater extraction well. I