Laserfiche WebLink
During 1985, natural erosion processes created severe mass wasting along <br />Wilson Creek, and for all intents and purposes destroyed this AVF. This impact <br />was not related to the mining operation. <br />However, the Division apparently never made an official determination that the segment of the <br />Wilson Creek valley impacted by the erosion and mass wasting no longer qualified as an alluvial <br />valley floor. This issue was revisited in association with Permit Revision 02. As described in <br />Section 2.06.8 of Volume 12, alluvium within the segment was down-cut 20 to 30 feet below the <br />former flood plain, leaving two narrow terraces high above the new incised channel, generally no <br />wider than 100 feet and in some areas much narrower. The down-cutting resulted in de-watering <br />of the alluvial aquifer, such that areas which may historically have benefited from sub-irrigation <br />no longer do. The narrow width and fragmented nature of the remnant alluvial terraces render <br />flood irrigation impractical. For these reasons, the Division has determined that the Wilson <br />Creek valley segment delineated as "Area Affected Bv_ 1985 Erosion And Mass Wasting Event" <br />on Map 11 A is not an alluvial valley floor. v <br />Other Stream Valleys in the General Area <br />Various other stream valleys with unconsolidated alluvial deposits in the mine vicinity may meet <br />alluvial valley floor criteria but have not been evaluated as a part of this review, because they are <br />located outside the proposed permit boundary, there is no proposed mine disturbance within their <br />watersheds, and as a result there is no potential for proposed mine operations to impact to the <br />valleys. These valleys include the East and West Forks of Wilson Creek, which are located <br />upstream of any proposed mining, the East Fork of Good Spring Creek, located upstream of any <br />proposed mining, and James Creek, located upstream of any proposed mining. <br />B. Primary Impacts <br />None of the four designated alluvial valley floors are within the area to be mined; therefore, <br />mining operations will not cause direct disturbance to any alluvial valley floors. Any mining <br />impact that might occur will be indirect in nature. <br />C. Secondary Impacts <br />It is believed that the areas to be mined presently contribute relatively little water to alluvial <br />valley floors. Any degraded water that might reach an alluvial valley floor would be diluted by <br />other sources. In addition, alluvial valley floors are protected by both stream buffer zones and <br />treatment of runoff from disturbed areas in sediment ponds. <br />The Gossard Loadout is located near the confluence of Wilson and Taylor Creeks and the <br />alluvial valley floor associated with Wilson Creek. There is a slight potential for waters of <br />degraded quality to reach alluvial materials near the loadout. An alluvial well located near the <br />loadout is monitoring this situation. Runoff from the surrounding areas above the loadout are <br />Proposed Decision and Findings of Compliance 14 September 2009 <br />Permit Renewal 05 Page 71