Laserfiche WebLink
yr <br /> M. <br /> VIA <br /> Work Plan Evaluation of Soil and Ground Water December 4, 1989 <br /> Unocal Station No. 6981, Stockton, California AGS 38032-3W <br /> MONITORING WELL CONSTRUCTION <br /> F <br /> The five monitoring wells will be constructed using thread jointed, 4-i nch-inner-diameter, <br /> Schedule 40 polyvinyl chloride PVC casing. No chemical cements, glues, or solvents will <br /> €' be used in well construction. The screened portion of four of the wells will consist of <br /> factory-perforated casing with 0.010-inch-wide slots. Because the monitoring well to be <br /> constructed near the north side of :he underground storage tanks will be used as an <br /> extraction well, if necessary, the screen portion will consist of continuously wrapped FVC. <br /> The spacing size of the continuously wrapped screen will be selected based on the field <br /> evaluation of site subsurface conditions. The ideal well screen of the five wells will extend <br /> from the total depth of each well to a point approximately S feet above thegrouno water <br /> surface. This screened interval will allow sampling of the air-water interface though <br /> expected seasonal groand-water fluctuations. However, the continuous log will be used to <br /> evaluate more precisely the thickness of the upper water bearing zone, to design the length <br /> of the well screen to meet site-specific conditions. <br /> The annular space of the well will be packed with clean Monterey sand to a depth <br /> approximately 2 feet above the slotted interval. The size of the sand pack will be selected <br /> to be compatible with the screen size selected. A surge block will be used to surge the <br /> monitoring well after the sand pack has been placed but before the bentonite plug is added. <br /> This technique will allow the ^-.nd pack to settle prior to the placement of the bentonitL <br /> v <br /> � 19 <br />