2012-03-15_REVISION - M1977300 - Laserfiche WebLink

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Whetstone' Associates The proposed monitoring depths range from 100 to approximately 1,000 feet (Table 1). The target depths are estimated and the final determination will be made in the field, based on the geology encountered during drilling. Table 1. Planned Bedrock and Alluvial Groundwater Monitoring Sites Well Location ID L2 Upgradient - Deep L4 L5 L6 L7 Location Description L1 Upgradient - Shallow 150 Background - replacement for MW 10 East of Schwartzwalder Mine, downgradient L3 relative to pre - mining static water level - Shallow East of Schwartzwalder Mine, targeting Schwartz Trend geologic transition zone, downgradient relative to pre- mining static water level - Deep Valley floor near alluvial well MW3A — Shallow Valley floor near alluvial well MW3A — Deep Alluvial well - southeast of the South Waste Rock Pile, near water treatment facility L8 Near south boundary of Section 25 L9 Near south boundary of Section 25 Technical Memorandum Expected Depth Purpose (ft bgs) 500 Background - replacement for MW 11 300 1,000 Determine vertical and horizontal gradients /directions Determine water quality in bedrock east of Schwartzwalder Mine Determine vertical and horizontal gradients /directions Determine water quality in bedrock east of Schwartzwalder Mine Target Illinois Fault, determine 100 alluvium/bedrock head differences, determine water quality in bedrock Target Illinois Fault, determine 200 alluvium/bedrock head differences, determine water quality in bedrock 30 300 800 Evaluate any potential groundwater impacts associated with South Waste Rock Pile Deferred. Determine the need for this well based on data obtained from L3 /L4 locations Deferred. Determine the need for this well based on data obtained from L3 /L4 locations NOTES: ' Target depths are estimated and the final determination will be made in the field, based on the geology encountered dunng dnllmg 2 bgs = below ground surface 2. WELL DRILLING Bedrock monitoring wells will be drilled using an air rotary rig. For wells drilled less than 300 ft depth, clean water or water with foam will be used as the drilling fluid. Injected water may be used for dust suppression during drilling at an injection rate of 2 to 5 gpm. Environmental -grade drilling foam may be added to assist in lifting drill cuttings from the hole at depth. The foam will be kept to the minimum required to suspend cuttings and clean the hole, and the water -foam mixture will typically use an injection rate of 2 to 5 gpm. The borehole diameter will be a minimum of 6.0 inches 4109C.120309 2