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b~Lde Bou(av. D,t1G <br />• © October l/.l99S <br />Page 1 <br />Locations of local water rights are shown on Exhibit 16-1. Attachment 16-1 contains a <br />separate report detailing the study of water rights in the vicinity of the Yoast mine and <br />augmentation plans for water supplies and rights in the mine area. Attachment 16-2 details <br />the study of long-term effects of pumpage from the proposed Yoast production well. <br />Additional information pertaining to water sources that will be monitored for potential <br />mining impacts is also contained in Tab 15 (Hydrologic Monitoring Plan) and Tab 18 <br />(Hydrologic Reclamation Plan). <br />As stated in Tab 17, there are no foreseeable mining impacts to water rights in the vicinity of <br />the Yoas[ mine, including chose in Sage Creek. No righted or unrighted wells exist within <br />[he areas proposed for mining disturbance. Thus, there is no potential for impacts to wells <br />from mining or related activities. No registered or unregistered surface water sources exist <br />in the Sage Creek drainage within the mine permit boundary. Adjacent water users, <br />identified in permit Tab 16, will not be impacted by pit pumpage drawdowns as all are <br />located well beyond the one-foot drawdown contours (see Exhibit 17-1 of Tab 17). As staced <br />in Tab 17, should any proposed or ongoing monitoring show that impacts to the local <br />groundwater systems preclude their use, SCC will provide alternative water sources of <br />comparable quantity and quality. <br />Surface Water and Groundwater Flow <br />As stated on page 14a of permit Tab 17, the Yoast production well will result in minor <br />streamflow depletion (4.9 acre-feet/year) in Sage Creek. The surface water flow impacts are <br />small in magnitude, of moderate extent (less than 10-mile radius for drawdowns of less than <br />one foot), and of limited duration (nine years of pumping and 20 years of recovery). Since a <br />portion of the surface water system is over-appropriated, a water augmentation plan was <br />developed by SCC and approved by the District Water Court. Per Tab 17, any minor <br />impacts to adjacent surface water users from pumping in the production well will be <br />mitigated according to the augmentation plan. <br />In regard to groundwater Flow impacts, mining and reclamation activities planned for Yoast <br />will no[ diminish the permeabilities of adjacent, undisturbed geologic units, including those <br />located adjacent to mined areas in Sage Creek. As stated in Tab 17, hydraulic conductivities <br />of replaced spoil material will be increased slightly both vertically and horizontally due to <br />the nature of spoil replacement. The increased spoil conductivity will result in a similar or <br />slightly higher vertical infiltration rate and higher transmissivities within the resaturated <br />portions of the spoil. Impacts of the mine spoil and topsoil replacement on groundwater <br />flow should be of minimal or negligible significance. Also, as stated previously, adjacent <br />groundwater users identified in permit Tab 16 will not be impacted by pit pumpage <br />drawdowns. <br />Surface Water and Groundwater Cbernistry <br />Loading calculations for discharge front replaced spoil on the quality of groundwater and <br />surface water in t}te Sage Creek drainage are addressed in Tab 17. The loading calculations <br />preserved in Attachment 17-5 show that the magnitude of the predicted localized increase in <br />total dissolved solids (TDS) for the bedrock aquifers due to activities at Yoast is large, <br />