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i 2.3.1 Shallow Monitoring Well Construction The shallow monitoring well will be ilnstalibd in an 8-inch diameter soil boring drilled by a truck- . i,,; mounted drill rig, equipped with hollow,st�em augers. .The shallow well will be constructed with �1" Ii .! 4 20 feet of two-inch diameter, Schedule 40, flush-threaded and machine-slotted (0.020-inch) polyvinyl chloride (PVC)well screenli: Given that the groundwater table is approximately 40 feet a`d u1 41 oil bgs, the well screen will span from approximately 30 to 50 feet bgs. Blank PVC casing will y , , .' s. thread into the top of the well screensir`a1ndlextend to the surface. �.. A filter pack of Monterey#3 graded.andwashed sand will be placed through the hollow stem { TI!ij! I "!€i 111 augers as they are slowly retrieved nd.until the sand pack reaches approximately two feet i -41 above the top of the screened inte"ri al: Overlying the sand pack, two feet of bentonite chips will be placed and hydrated within the annular space between the borehole and the well casing. Over the hydrated bentonite, a surface seal of neat cement grout will be installed with a tremie i; 1 pipe. The top of the well will be'secured with a water-tight locking cap and an above-grade stave pipe monument. ' 2.3.2 Deep Monitoring Well Construction The deep monitoring well will be installed to investigate the first deeper groundwater-bearing d zone below the9 roundwater table:�:The'depth and construction of the proposed deep well will be based on the soil stratigraphy obtained from the proposed co-located CPT boring. a located outside of the plume of impacted roundwater, a Since the deep well w€II presumably,be p p g , ., conductor casing will not be used to seal'off the overlying groundwater during drilling. The deep monitoring well will also be installed m,an 8-inch diameter soil boring drilled with hollow-stem augers. To evaluate and monitor the extent of impacted groundwater detected at MW-5, the deep well should be constructed similar to MW-5. Currently, the groundwater table is approximately 17 LI feet above the top of the MW-5'weilscreen. Monitoring well MW-5 was installed in May 1994 to 1a'i`. a total depth of 75 feet and a screen'mterval spanning from 55 to 75 feet bgs. As such, unless field observations dictate otherwise;the proposed deep well will consist of 20 feet of two-inch diameter, Schedule 40, flush-threaded and machine-slotted (0.020-inch) PVC well screen from i approximately 55 to 75 feet bgs. Blank.PVC casing will thread into the top of the well screen } and extend to the surface. . i 8