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August 6, 1991 J ARCO Station No. 548 at the margins of the site. Tne locations of the proposed wells are shown on Plate 4. Monitoring wells will be constructed in the borings with thread jointed, 4-inch-inner- diameter, Schedule 40 polyvinyl chloride (PVC) casing. No chentical cements, glues, or �th solvents will be used in well construction. The screened portion of each well will consist of ` l&�� factory-perforated casing with 0.020-inch-wide slots. The well screen will extend from the-00'L�i� total depth of the well to approximately 5 feet above the ground-water surface. This screened interval will allow sampling at the air-water interface during seasonal fluctuations of the ground-water level. The annular space in the well will be packed with number 3 sand to approximately 1 to 2 feet above the slotted interval A 3-foot�h�ick bentonite plug will be added above the sand pack to prevent the cement from entering the well pack. The remaining annulus will l:e backfilled to grade with a bentonite cement slurry. Well ;E construction details are F resented in the Schematic Well Design (Plate 5). } ted with a traffic-rated, cast-aluminum utility box equipped Monitoring wells will be protec a watertight ser l to protect against surface-water infiltration with a PVC skirt. The box has and must be opened with a special wrench. The design of this box discourages vandalism and reduces the possibility of accidental disturbance of the well. Vadose-Well Construction Soil borings chosen for vapor wells (two total) will be located in soil containing elevated E levels of hydrocarbons based on field observations and field screening using s PID. If subjective evidence of hydrocarbons(e.g.discoloration)is observed by the geologist,d PoID readings on collected soil samples are above 50 ppmv, the boring will be convert vadose well. Plate 4 shows the approximate locations of the proposed vapor wells. t 10 AGS 3OW4-4 .e..�...esLrs,nnwsmnnm�s�amr:fn�uta��