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January 30, 1987 <br />Project 116-1.5 <br />Four wells will be located generally down -gradient of the landfill trenches <br />to monitor ground water that could be affected by the landfill. Two wells <br />will be located upgradient of South Little Johns Creek. One well will be <br />located directly upgradient of the landfill to determine the recharge <br />characteristics of South Little Johns Creek into the ground water. Water <br />level measurements will be obtained from this well on a regular basis. It <br />will be sampled for water quality only for the SWAT report unless it is <br />shown that recharge from the creek is influencing ground water quality <br />beneath the landfill, in which case it will become part of the regular <br />monitoring program. Surface water from the creek will be analysed to aid <br />in this determination. <br />Phase 2 <br />The second phase will be the installation of monitoring wells with deeper <br />screen intervals. The screen lengths will be no greater than 10 feet, and <br />will be located approximately 50 feet deeper, depending on subsurface <br />geology, than the screen intervals in the shallower wells. These wells <br />will be used to provide information about vertical ground water gradients, <br />and to determine water quality in deeper permeable zones. Two of these <br />wells will be located downgradient of the landfill, and one will be south <br />of South Little Johns Creek. Exact locations of these wells will be based <br />on the subsurface conditions encountered during phase 1, and changes in <br />ground water gradient direction that have been observed in the past. <br />'Drilling and Sampling <br />The borings will initially be drilled with eight inch diameter hollow stem <br />augers. A detailed description of the subsurface geology will be obtained <br />using continuous sampling techniques. Shelby tubes will be used, if <br />possible, to obtain soil samples for hydraulic conductivity testing. The <br />boring will then be reamed to 10.5 inches diameter using the mud rotary <br />method to provide a bore hole large enough for proper monitoring well <br />construction. Geophysical logs will be generated using these open <br />boreholes before the wells are constructed. <br />All drilling and sampling equipment will be thoroughly steam cleaned <br />between drillholes to prevent cross contamination. Additionally, sampling <br />equipment will be steam cleaned between sampling drives. <br />Monitoring Well Construction <br />Well Casing <br />General monitoring well construction details for the proposed wells are <br />shown on Figure 2. Four inch diameter, threaded, schedule 40 PVC <br />wire -wound screen and blank casing will be suspended in a 10.5 inch <br />diameter borehole. Although stainless steel screen is stronger and more <br />