2011-12-06_REVISION - C1980001 (3)

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Alluvial Valley Floor Identification Information"on alluvial valley floors can be found =Volume 2,`-Section 2.4; Volumes 3 and 4, Section 2.5; Volume 5, Section 2.9 ; Volu nes:1 l and 12, - •Section 4.6 of the PAP. The Division has previously found an approximate 700 -acre strip of alluvium along Trout Creek to meet the "regulatory definition of an alluvial valley floor (AVF). -The AVFis the area underlain by-the "two "water - bearing terraces of Trout `Creek-alluvium e , r that ' to as Qtl 'aiid=Qt2,'-as shown On'Map'2.5 -21 of the PAP.. :The AVF- "designation'is based on the presence of unconsolidated stream -laid deposits and -the presence of water In sufficient quantity and quality for flood irrigation or sub - irrigation agricultural activities. Qtl is Trout - Creek's active alluvial floodplain. Qtl'ishydrologically connected to - Trout Creek. `Qtl contributes baseflow to Trout Creek duringlow -flow periods, and is recharged 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 discharge from Qt2 eventually reaches Trout Creek via seeps 'along}he:bedrock that crops out along the creek. Qt2 is recharged by infiltrating meteoric waters. The operator Calculated the mean annual water yield of Trout Creek at a point immediately downstream °of°'the ' mine site a`s` 37,500 acre -feet /year, indicating that an ample supply of water is available for floodirngation purposes. Irrigation is conducted in the Trout Crek AVF Ditches a rid. flood'it'rigatedland are shown on Map '4.6:16 of the PAP. PAP, Section 2.9.3.2 and Exhibit 3.7 -1) C 1980 -001 Edna Mine Permit Renewal No. 6 29 Subirrigation potential exists on the Qtl terrace of Trout Creek :'Species olvegetation on the Qtl terrace which are indicative of subirrigated conditions are delineated on Map 2.4 - }1' of the PAP. Ground" water' levels observed in the alluvium along Trout` Creek also indicate that subirrigatiori occurs. Depths to water ranging froth one to six feet have been observed during monitoring. ' The' operator has presented land use "information on Exhibit 2.9 -1 of the`PAP. 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 signifida ice of the hayproduction on'Trouttreek AVF portions of the individual farming units: This expressed in terms of "percent of total hay production" for each 'individual This` information indicates that the hay production on the Trout Creek AVF is significant to the farming units in the vicinity of the mine.