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downstream of the mine site as 37.500 acre-feet/yeaz, indicating that an ample supply of water is <br />available for flood irrigation purposes. Current irrigation activities do occur within the Trout Creek <br />AVF study area. Map 4.6-16 of the permit application delineates ditches and flood irrigated land. <br />Sub-irrigation potential also exists on the Q,1 terrace of Trout Creek. Map 2.4-1 of the permit <br />application delineates those species of vegetation on the Q,1 terrace which are indicative of <br />sub-irrigated conditions. Groundwater levels observed in the alluvium along Trout Creek also <br />indicate that sub-irrigationoccurs. Depths to water ranging from one to six feet have been observed <br />during monitoring. <br />The operator has presented land use information on Exhibit 2.9-1 of the permit application. Land <br />use along the Trout Creek AVF consists of cropland, pasture, and shrub and brush rangeland. <br />Irrigated native hay is produced by several farms in the vicinity of the permit azea. The operator has <br />also assessed the significance of the hay production on Trout Creek AVF portions of the individual <br />farming units. This is expressed in terms of "percent of total hay production" for each individual <br />farm (section 2.9.3.2 and Exhibit 3.7-1). This information indicates that the hay production on the <br />Trout Creek AVF is significant to the farming units in the vicinity of the mine. <br />Effects of Mining on Identified Alluvial Valley Floors <br />No mining occurred within the Trout Creek alluvial valley floor. Therefore, the AVF was not <br />physically disturbed. Because mining did not extend onto the alluvial valley floor boundary, direct <br />impacts resulting from the physical disruption of alluvial and/or channel materials did not occur. <br />However, secondary effects, including minor dewatering of the alluvium and water quality impacts <br />due to the leaching of dissolved salts from the spoil material, have been identified and have the <br />potential to impact the AVF. The significance of these secondary impacts are discussed below. <br />Dewatering of the Alluvium <br />Mining operations in both the West Ridge and Moffat Areas experienced minor mine inflows from <br />the alluvial terraces directly related to distance of the mining edge to the AVF alluvium. In general, <br />the further away the operations were from the creek, the less the inflow. <br />The original permit application indicated that mining would induce inflows from the Trout Creek <br />alluvium. This impact occurred in both the West Ridge and the Moffat Areas where the floor of the <br />box cut was at an elevation below the alluvial water table elevation. Mining created a gradient that <br />allowed alluvial groundwaterto enter the pit following migration through the undisturbed materials <br />between the box cut and the alluvium. <br />Data submitted by the applicant illustrate that impact to the alluvium was minimal with a gradual <br />lowering of the water level. The amount of flow from the alluvium into Trout Creek was negligible <br />when compared to the total flow of Trout Creek. The impacts observed were temporary in nature <br />occurring only for the duration of mining. <br />Edna Mine 26 Penni~ Renewal No. 3 <br />