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Whetstone, Associates Technical Memorandum • 10 ft of 0.02 -inch (20 -slot) factory slotted Schedule 40 or 80 PVC screen • 5 -ft sump (blank 2" Schedule 40 or 80 PVC casing) installed below the screen • Centralizers will be placed above and below the screen and at least every 40 feet within the blank section of casing above the screen. • 10 -20 Colorado silica sand filter pack • Filter pack will be tremmied into place and tagged at 3 — 5 ft above the top of the screen. • Filter pack will be surged (mechanically agitated and settled) before installing the seal. • Annular seal will consist of bentonite chips to 5 ft below ground surface. • Casing will be set or cut so that the inner PVC well casing is 22 — 24 inches above ground surface. • Surface completion will include an outer steel casing and 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 will be padlocked (typically with keyed alike locks 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 clean latex or nitrile gloves while handling casing). An example well completion diagram for Shallow PVC wells is provided in Figure 3. 5.2 Well Specifications for Deep Wells (500 —1,000 ft) Deep monitoring wells will be drilled using an air rotary rig with water or foam as the drilling fluid. The borehole diameter will be a minimum of 9 inches. Deep monitoring wells will be completed using 3 -inch ID 304 stainless steel casing and 0.02 -inch (20 -slot) wire -wound 316 stainless steel screen. Monitoring well casing material will meet hang weight, tensile strength, and collapse strength requirements for the proposed setting depths. Well completion specifications for deep wells (500 — 1,000 ft depth) are as follows: • 3 -inch ID stainless steel 304 casing, flush - threaded, Schedule 40 (0.22 wall thickness). • 40 ft of 0.02 -inch (20 -slot) wire -wound screen, 3 -inch ID stainless steel 316. • 5 -ft sump (3" Schedule 40 stainless steel 304 casing) installed below the screen. • Centralizers will be placed above and below the screen and every 60 feet within the blank section of casing above the screen. • 8 -12 Colorado silica sand filter pack. • Filter pack will be tremmied into place and tagged at 10 ft above the top of the screen. • Filter pack will be surged (mechanically agitated and settled) before installing the seal. • 10 -ft seal of coated bentonite pellets will be tremmied into place, directly above the sand pack. I Note that the 3 -inch ID casing diameter was selected to be large enough to accommodate either portable sampling pumps or dedicated pumps set in the target horizon, and small enough to minimize the purge volume and purge water disposal requirements. 4109C.120309 8