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Work Plan For Monitoring Well(MW-8)Installation 2130 West Washington Street Facility Stockton,California Sierra-Pacific Project No.95-119.02 have low levels of nitrogen because the new well is being placed in a peripheral area. Rinsates and purge water will be discharged to the sanitary sewer. v., 3.3 Well Installation and Development The monitoring well will be constructed using flush-threaded sections of 2-inch (diameter) polyvinyl-chloride (PVC-Schedule 40) casing. A flush-threaded PVC end-cap will be placed at the bottom of the well casing. PVC well screens, with 0.010 screen slots, will be placed within --- a 15-foot interval, from 5.0 to 20.0 feet bgs. Water-level measurements indicate that the saturated zone fluctuates from 8.9 to 15.8 feet bgs. The top of the screened interval will be above the highest observed west-area water level, yet deep enough to allow proper sealing and wellhead placement. Unconsolidated sediment present within the uppermost saturated zone,5 to 20 feet bgs, consists largely of poorly-graded, silty-sand with traces of smectite clay(USCS, SM). A medium-grained filter sand will be used to pack the well screens (RMC Lonestar #2-12 or equivalent product). It is anticipated that at least 95 percent of the filter pack will be retained by the 0.010 slotted screens. Adjustments to the well design, screen size selection, and filter sand application may be made in the field if subsurface information indicates a need to modify this plan. The monitoring well will be gently surged to consolidate the filter pack before placing the bentonite seal. Additional sand will be placed in the well to allow for settlement and wash-out. The filter pack will be followed with three feet of Enviroplug bentonite chips. The remaining two feet of open boring will then be filled with Portland cement concrete. A schematic drawing of the well design is shown on Figure 4. The well will be completed by installing a three-foot, 6-inch-diameter, steel, stand-pipe in Portland cement concrete. The stand-pipe, and an expansible two-inch-diameter stopper-plug,will be locked to reduce the likelihood of vandalism. -� Sierra-Pacific Groundwater Consultants 3