Laserfiche WebLink
RESPONSE. If the surface or groundwater flow in Grassy Valley is identified as having <br /> been impacted by mining operations, the impacts will be addressed as to flow quantity by <br /> augmentation, and as to quality by interception of impacted water leaving the mining <br /> operation (in particular from the toe of the ECOSA) by collection, treatment as necessary, <br /> and direction of the resulting flow into the diatremal rockmass. <br /> How will reducing the Grassy Valley catchment area impact the creek flow? <br /> RESPONSE: No reduction of the Grassy Valley catchment area is proposed in <br /> Amendment 11. <br /> Are additional water rights required for reducing this catchment basin? If so, have <br /> they been obtained? <br /> RESPONSE: No reduction in the catchment basin area is proposed in Amendment IL <br /> Newmont maintains a water rights augmentation plan that addresses water rights in the <br /> district. <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 of <br /> surface runoff will be prevented from exiting the mine footprints during operation. The <br /> flow reduction will primarily occur in the Poverty Gulch catchment, with a smaller <br /> reduction occurring in Grassy Valley. Are additional water rights required for these <br /> reductions to flow? If so,have they been obtained? <br /> RESPONSE: The "estimated 2 gpm of surface runoff' identified in the report is for the <br /> total project through Amendment 11, and is unchanged from Amendment 10, as the water <br /> capture is unchanged. As noted above, an augmentation plan is in position to <br /> accommodate reductions in surface water flow in the Grassy Valley catchment area due to <br /> surface capture. CC&V(now Newmont) is currently negotiating a modified agreement for <br /> water rights augmentation with potentially affected water rights holders. Potential flow <br /> changes in Poverty Gulch and Grassy Valley are directly addressed in that agreement. <br /> • Page 16: Under Item#2—Seepage from Mines,the text states that"Based on the Carlton <br /> Tunnel flow evaluation in Section 3.4.1 above, the increased infiltration while disturbed is <br /> estimated at 25%, resulting in an approximate 100 gpm increase in flow to Carlton Tunnel <br /> during operation." Considering that current Carlton Tunnel flow is estimated to be <br /> approximately 1,690 gpm, how did you calculate a 25% increase of only 100 gpm? <br /> 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 the <br /> operation?Does the sediment pond system located at the Carlton Tunnel portal have <br /> sufficient capacity to accommodate this amount of increased flow? <br /> RESPONSE. The 25%increase in infiltration in the report refers to the expected difference <br /> between infiltration through natural or reclaimed surfaces and infiltration through disturbed <br /> surfaces in unreclaimed surface mines and overburden storage areas. The increased <br /> infiltration in unreclaimed areas does not directly translate into increased flow from the <br /> Carlton Tunnel, because much of the increased infiltration is retained in the overburden as <br /> its moisture content increases to reach the field capacity. Only when this threshold is <br /> reached is there gn <br /> X seepage flow through the overburden materials. The 100 gpm estimate <br /> is the expected flow change resulting from the interplay of these two effects, and it reduces to <br /> close to zero after final reclamation of the mine site. <br /> 3.6.2 Impact of Drainage of the East Wall of East Cresson Mine (WHEX)on Surface Vegetation in <br /> Page 5 of 28 <br />