2012-03-09_REVISION - M1977300 - Laserfiche WebLink

Home Browse Search

Whetstone, Associates Technical Memorandum • Annular seal of high - solids bentonite grout will be tremmied into the annulus from the pellet plug seal to 20 feet below ground surface. (Alternatively, a Portland cement grout could be installed from the top of the pellet plug seal to ground surface, provided the casing collapse strength can withstand the added weight of the cement.) • The upper 19 feet of annular space will be filled with Portland cement (6 gal /sack). • All materials will be placed by tremie pipe, either by gravity or by pumping. • Casing will be cut so that the inner well casing is 22 — 24 inches above ground surface. • Surface completion will include a locking steel well cap set in a concrete pad that slopes slightly away from the well. • Two to three traffic posts (bollards) will be installed around the surface completion and painted orange. One traffic post shall be removable for access during sampling. • All well locks will be keyed alike using keys provided by Cotter or its consultants. Well drilling and construction will follow standard practices for environmental monitoring wells (including non - metallic environmental pipe dope on drill rods and wearing latex gloves while handling casing). An example well completion diagram for Deep Stainless Steel wells is provided in Figure 4. 6. WELL DEVELOPMENT Monitoring wells will be thoroughly developed to remove residual drilling fluids and cuttings. Well development will be conducted by airlifting from above the screen and surging within the screened zone using a double surge block. The water produced during well development will be discharged to the drilling pits. The supervising hydrogeologist or geologist will monitor the discharge water during well development. Wells will be developed until the water is dear without visible turbidity, and successive measurements for field parameters vary by less than 10 percent or 0.1 pH unit. A groundwater sample may be collected for laboratory analysis at the end of well development. 7. ADDITIONAL CONSIDERATIONS 7.1 Drilling Contractor Availability and Access Preliminary contact with drilling contractors has indicated that many drilling companies are already committed for the summer 2012 field season, and are not taking additional jobs. Due to the steep grade and narrow switchbacks on the access road, a standard drill rig may not be able to reach the L1, L2, L3, and L4 locations. A track - mounted or articulated rig could be required, which further limits the availability of contractors because these drilling rigs are less common. 7.2 Low Well Yield The bedrock wells are expected to produce less groundwater than a standard alluvial monitoring well. If yields are low, development of the wells may be limited to flushing of the borehole with clean water prior to installing the casing and filter pack, and then repeatedly bailing the wells dry. If this method of development is required, the same well development criteria will be applied (no visible turbidity and stable field parameters) as for higher yield wells. 4109C.120309 9