WORK PLANS_CASE 2 - Laserfiche WebLink

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Well Construction The two new monitoring wells will be constructed of four-inch diameter, schedule 40, PVC blank casing with twenty feet of 0.02 slotted screen at its bottom (Figure 3). Typically fifteen feet of perforated casing will extend below the water table surface and the remaining five feet will extend above it. The annular space between the perforated casing and the excavation wall will be sand-packed with Lapis Luster#lc sand to a level two feet above the screened interval. A one-foot spacer of bentonite pellets or crushed natural bentonite granules will be placed directly above the sand pack. All depths of sand pack and bentonite seal will be verified by sounding with a weighted tape. The remaining annular space will be filled up to the surface with a neat cement/bentonite grout. This design matches the three existing monitoring wells that were installed in 2002. Surface completions of the wells will depend on the protective needs for each well. In areas of low probability of damage the top of each well will be just below grade and the casing will be capped with a flush mounted"ChristyTM type" box. In areas of higher damage probability, the well will be completed above grade with a three-foot steel standpipe and a locked cap. Upon completion and development of the new groundwater monitoring well installations a dedicated bladder pump (QED Model P1101M) will be installed into each well. Construction details of each well will be recorded and presented in a final report. All remaining borings not converted to monitoring wells will be backfilled and grouted using neat cement/bentonite grout flush with the surface. Well Development All wells will be fully developed to the extent practical in order to improve hydraulic continuity with the native matrix. Development will be performed using pumping, bailing or surging of the well to a sediment-free state. All water volumes will be recorded along with periodic pH and conductivity measurements. Development will cease when the well produces little or no fine sediment and the water parameters have stabilized. Surveying of Wells Within one month of completing the well installations and prior to the subsequent regular quarterly sampling a State-licensed surveyor will survey the new wells relative to Table 1 (vertical datum) and NAD83 per Table III (horizontal datum) of the Tracy Modified Coordinate System the existing monitoring wells located on the site.