GENERAL33542 - Laserfiche WebLink

Home Browse Search

Qtl is Trout Creek's active alluvial floodplain. Qtl is hydrologically connected to Trout Creek. Qtl contributes baseflow to Trout Creek during low-flow periods, and is rechazged by Trout Creek during the rest of the year. Qt2 is older than Qtl and consists of alluvial terrace deposits. Qt2 contains a perched aquifer that overlies bedrock. The bedrock hydrologically separates Qt2 from Qtl. Any dischazge from Qt2 eventually reaches Trout Creek via seeps along the bedrock that crops out along the creek. Qt2 is rechazged by infiltrating meteoric waters. The operator calculated the mean annual water yield of Trout Creek at a point itrunediately downstream of the mine site as 37,500 acre-feedyeaz, indicating that an ample supply of water is available for flood irrigation purposes. Irrigation is conducted in the Trout Creek AVF. Map 4.6-16 of the permit application delineates ditches and flood irrigated land. Sub-irrigation potential exists on the Qtl terrace of Trout Creek. Map 2.4-1 of the permit application delineates those species of vegetation on the Q,1 terrace which aze indicative of sub-irrigated conditions. Ground water levels observed in the alluvium along Trout Creek also indicate that sub-irrigation occurs. Depths to water ranging from one to six feet have been observed during monitoring. The operator has presented land use information on Exhibit 2.9-1 of the permit application. Land use along the Trout Creek AVF consists of cropland, pasture, and shrub and brush rangeland. Irrigated native hay is produced by several farms in the vicinity of the permit area. The operator has also assessed the significance of the hay production on Trout Creek AVF portions of the individual farming units. This is expressed in terms of "percent of total hay production" for each individual farm (section 2.9.3.2 and Exhibit 3.7-1). This information indicates that the hay production on the Trout Creek AVF is significant to the farming units in the vicinity of the mine. Physical Disruption of AVF by Mining Mining operations did not extend into the Trout Creek alluvial valley floor; consequently, the AVF was not physically disturbed. DewaterinQ of Trout Creek Alluvium An analysis done by the Division showed that a maximum drawdown of 1.6 feet could occur where Trout Creek alluvium is nearest the West Ridge box cut. Data from the alluvial wells do not indicate that drawdown to this degree has occurred; only a seasonal fluctuation in water level is apparent. The slight reduction in sub-irrigation potential was predicted in the irrigated cropland near the West Ridge mining area due to temporary alluvial aquifer drawdown. This reduction did not significantly affect hay production. The irrigated croplands on the west Edna Mine 27 Permit Renewal No. 4