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<br />modern floodplain. Recharge of the Qt2 terrace is from infiltration of <br />local precipitation only, and not from any type of hydrologic connection with <br />the active Trout Creek floodplain. On the permit area (east) side of Trout <br />Creek, only the Qtl predominates, although the Qt2 terrace is present on a <br />limited basis. <br />The operator calculated the mean annual water yield of Trout Creek at a point <br />immediately downstream of the mine site as 37,500 acre-feetlyear, indicating <br />that an ample supply of water is available for flood irrigation purposes. <br />Current irrigation activities do occur within the Trout Creek AVF study area. <br />Map 4.6-16 of the permit application delineates ditches and flood irrigated <br />land. <br />Sub-irrigation potential also exists on the Qtl terrace of Trout Creek. Map <br />2.4-1 of the permit application delineates those species of vegetation on the <br />Qtl terrace which are indicative of sub-irrigated conditions. Ground water <br />levels observed in the alluvium along Trout Creek also indicate that <br />sub-irrigation occurs. Depths to water ranging from one to six feet have been <br />observed during monitoring. <br />The operator has presented land use information on Exhibit 2.9-1 of the permit <br />application. Land use along the Trout Creek AVF consists of cropland, <br />pasture, and shrub and brush rangeland. Irrigated native hay is produced by <br />several farms in the vicinity of the permit area. The operator has also <br />assessed the significance of the hay production on Trout Creek AVF portions of <br />the individual farming units. This is expressed in terms of "percent of total <br />hay production" for each individual farm (section 2.9.3.2 and Exhibit 3.7-1). <br />This information indicates that the hay production on the Trout Creek AVF is <br />significant to the farming units in the vicinity of the mine. <br />Oak Creek also has sufficient associated alluvium and available water to be <br />considered an AVF. Similar to Trout Creek, two levels of terraces exist, with <br />the Qtl terrace being the modern floodplain. Ground water contained in this <br />terrace is hydrologically connected to Oak Creek. The Qt2 terrace is <br />limited in area in this portion of the permit area and does not contain <br />significant amounts of ground water. <br />The applicant has estimated that the mean annual water yield of Oak Creek is <br />approximately 7,900 acre-feet/year, indicating that ample water would be <br />available to support irrigation practices in this drainage. At this time, <br />however, irrigated agriculture is not practiced in the Oak Creek AVF study <br />area. Exhibit 2.9-1 of the permit application indicates that current land use <br />of the Oak Creek AVF is shrub and brush rangeland. In the vicinity of the <br />Edna Mine, the Oak Creek valley is either undeveloped rangeland not <br />significant to farming, or has been disturbed. There is only a limited amount <br />of flood-irrigable alluvial terrace lands available for agricultural use. <br />Vegetative species indicative of sub-irrigated conditions also exist along Oak <br />Creek. These areas are shown on Map 2.4-1 of the permit application. The <br />presence of the indicator species, and ground water depth of less than 6 feet, <br />support the conclusion that the Oak Creek AVF maintains a sub-irrigation <br />potential. <br />-30- <br />