GENERAL41505 - Laserfiche WebLink

Home Browse Search

1. The proposed mining operations would not interrupt, discontinue, or preclude farming on the alluvial valley floor. The surface facilities associated with the mine are located outside of the area designated as ailuvtal valley floor. The proposed operation would undermine portions of the area designated as alluvial valley floor but this is not expected to affect farming activities. The applicant has proposed limited mining (the extraction ratio wail be between 50 and 55 percent), and, therefore, no significant surface effects from subsidence are expected. In addition, the applicant has proposed a subsidence monitoring plan tSection 2.05.6(6)(f)(1i)(c) of the permit application) to verify the predicted effect. The proposed mining operation would not materially damage the quantity or quality of surface and ground water which supply the alluvial valley floor. During mining operations, the proposed underground mine would slightly deplete flows in the stream/alluvial aquifer system, and the discharge of water from the underground workings would affect water quality in the Carbon Ditch and in Ward Creek. After mining operations, when the natural ground water flow pattern is restored, water passing through the underground workings would affect water quality in the Williams Creek and Ward Creek streamlalluvial aquifer system. A quantitative assessment of these effects is provided in the discussion of probable hydrologic consequences contained in this findings document. That assessment predicts the streamflow depletion to be less than 2 percent of the average streamflow in Ward Creek, and less than 7 percent of the lowest streamflow observed in Ward Creek. The predicted water quality resulting from the mining activities would not prevent the use of surface water for flood irrigation. The essential hydrologic functions of the alluvial valley floors would be preserved. The most important characteristics of the Williams Creek and Ward Creek alluvial valley floors are the integrity of the present irrigation system and the ability of the surface water system to supply sufficient irrigation water to farming activities on the alluvial valley floors. As discussed above, surface disturbances would be located outside of the alluvial valley floors, and mining would be limited to 50-55 percent extraction to minimize surface subsidence effects. Any surface effects are anticipated to be minor, and capable of remedy. The operator has committed to promptly regrading depressions, swells or cracks if any develop as a result of subsidence. As a result, the surface topography and the integrity of the existing irrigation system would be preserved. Since no significant effect to the quantity or quality of the water which supplies the alluvial valley floor is expected, the supply of irrigation water would also be preserved. _pl_