2019-05-29_REVISION - C1981018 (11)

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40 Scullion Gulch Alluvial Valley Floor Determination The Division and OSM concluded that Scullion Gulch is not an alluvial valley floor. White River Alluvial Valley Floor Determination On the basis of available annual water yield, the presence of unconsolidated streamlaid deposits, the availability of supplemental moisture through subirrigation, and the presence of established irrigated lands, the Division and OSM identify the White River and its associated alluvial deposits as an alluvial valley floor. The permittee has supplied sufficient information to address material damages to the White River AVF. For the most part, the White River lies outside the permit area. Mining will not take place beneath the river or its alluvial deposits. The permittee has adequately demonstrated that bedrock contributions of ground water from the area to be mined are insignificant in relation to the flows observed in the White River. Flows to the White River from Red Wash and Scullion Gulch, which may be impacted by mining, are also insignificant in relation to the flows observed in the White River. By minimizing disturbances to Red Wash and Scullion Gulch during mining, the White River will not suffer material damage via either of these drainages. At the time of the original permit issuance, Kenney Reservoir, which presently exists within the project area, had not yet been filled. As such, the original findings document for the Deserado Mine contained an assessment of the potential for material damage to occur to the White River AVF as a result of the permittee’s proposed pumping of water from the AVF for use in the mine. The permittee had demonstrated that the volume of water removed from the alluvium was insignificant to the flow volumes observed on the White River even during low flow years, and had concluded that the effects of drawdown on the alluvial water body would not significantly impact farming due to the exclusive use of artificial flood irrigation practices in the area rather than natural sub-irrigation. This was felt to be a reasonable conclusion; however, it was also felt that natural sub-irrigation might provide additional, supplemental moisture to flood irrigated crops. In view of this, two stipulations were attached to the permit to provide for ongoing monitoring of the alluvial body to verify the anticipated drawdowns caused by pumping, and to provide for the development of a mitigation plan to protect farming operations in the event that drawdown of the White River alluvial aquifer had a detrimental effect on established agricultural activities. A monitoring plan was subsequently approved and implemented, thereby resolving the requirements of the stipulation. The approved plan called for monthly monitoring of six alluvial wells installed within the White River alluvium above, below, and adjacent to the alluvial well field utilized to supply water to the mining operation. At present, only one well, Qal-5, is monitored due to the complete inundation of the remaining wells by rising water levels from the gradual filling of Kenney Reservoir. A raw water lagoon was constructed within the vicinity of the alluvial well field at the