Information Center


FAQs

Will our “cone of depression” extend to the Sheep Creek alluvium?

The cone of depression over the mine area extends slightly into the Sheep Creek alluvium with the largest drawdown near the western and southwestern edge of the alluvium. The drawdown in the alluvium adjacent to Sheep Creek is one foot. This indicates that the drawdown in the alluvium has the potential to slightly deplete flows in Sheep Creek. The numerical model shows that the potential maximum depletion in Sheep Creek is approximately 0.45 cfs (~200 gpm). The base flow (lowest yearly flow) of Sheep Creek is 6700 gpm, so our maximum effect on Sheep Creek could be 3% of its flow. We will be replacing more than this with our mitigation plan. The water rights mitigation plan offsets all of the depletion from mine dewatering and our consumptive use. Since we are in a closed basin for water rights, the mitigation plan includes offsetting all consumptive use of groundwater by retiring surface water irrigation rights that will directly supplement flows in Sheep Creek at a rate equal to the consumptive use of the project (210 gpm). The mitigation water remains in Sheep Creek or is stored in a mitigation reservoir for release during the non-irrigation season. The mitigation reservoir location ensures any water that is released from the reservoir enters the Sheep Creek surface water system upstream of the stream sections.