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Cresson Project – AM-11 Adequacy Review <br />Page 2 <br />May 03, 2016 (Revised May 31, 2016) <br /> <br /> <br />3.4.3 Grassy Valley Perched Water Table <br /> Page 12: The text states “The existence of the perched aquifer in Grassy Valley is an <br />important aspect of the valley, because it holds groundwater near the ground surface, <br />and prevents all the water in the alluvium from draining into the underlying bedrock.” <br />This perched aquifer is said to have a water table between 0-50 feet of the ground <br />surface. Considering this information, could the perched aquifer be impacted by <br />mining activities (e.g, ECOSA, WHEX)? How will you sufficiently monitor <br />Grassy Valley for impact? If impacted, what remediation is anticipated? How <br />will reducing the Grassy Valley catchment area impact the creek flow? Are <br />additional water rights required for reducing this catchment basin? If so, have <br />they been obtained? <br />3.6.1 Impact of Additional Surface Mining on Streamflow and Groundwater Flow <br /> Page 16: Under Item #1 - Surface water flows, the text states that an estimated 2 gpm <br />of surface runoff will be prevented from exiting the mine footprints during operation. <br />The flow reduction will primarily occur in the Poverty Gulch catchment, with a <br />smaller reduction occurring in Grassy Valley. Are additional water rights required <br />for these reductions to flow? If so, have they been obtained? <br /> <br /> Page 16: Under Item #2 – Seepage from Mines, the text states that “Based on the <br />Carlton Tunnel flow evaluation in Section 3.4.1 above, the increased infiltration <br />while disturbed is estimated at 25%, resulting in an approximate 100 gpm increase in <br />flow to Carlton Tunnel during operation.” Considering that current Carlton <br />Tunnel flow is estimated to be approximately 1,690 gpm, how did you calculate a <br />25% increase of only 100 gpm? Should the increase be more on the order of <br />422.5 gpm, giving a total increased flow of approximately 2,112.5 gpm during <br />the operation? Does the sediment pond system located at the Carlton Tunnel <br />portal have sufficient capacity to accommodate this amount of increased flow? <br />3.6.2 Impact of Drainage of the East Wall of East Cresson Mine (WHEX) on Surface Vegetation in <br />Grassy Valley <br /> Page 17: Was the title supposed to read “…on Surface Water Flow in Grassy <br />Valley” rather than “…Surface Vegetation in Grassy Valley”? If so, please <br />correct this title to prevent any confusion it may cause. <br /> <br /> Page 17: The text lists two reasons why there will be no impact due to drainage to the <br />mine, including the head elevation of the water in the Precambrian wall rock being <br />lower than the base of the mine, and the up to 1,000 feet of unsaturated rock between <br />the base of the Grassy Valley aquifer and the top of the zone of saturation in the <br />diatreme will prevent any impact to Grassy Valley due to water pressure changes. <br />Considering that up to 700 feet of Precambrian rock in the headwaters of <br />Grassy Valley will be mined out in the WHEX pit, please expand on your answer <br />as to how this will not cause inflow into the mine from surrounding rock, <br />reduction in head in the Grassy Valley aquifer, and/or impacts due to reduction <br />in head in the surrounding valley. <br />