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precluded by the low vertical permeabilities between the Wadge seam and the alluvia. <br /> Stream flow loss to surficial tensional cracks which may develop is expected to be <br /> minimal and the fine-grained nature of the alluvium will rapidly fill any cracks that <br /> may develop. Furthermore, surface cracking due to subsidence is typically limited to a <br /> maximum of 50 feet in depth and direct connection to the workings is not anticipated <br /> due to overburden depths in this area in excess of 600 feet. Also, any stream flow loss <br /> will be more than compensated by the projected and existing mine discharge to Foidel <br /> Creek averaging over 600 gpm. And lastly, the entire Foidel Creek/Middle Creek <br /> Confluence alluvial valley floor is flood irrigated by water diverted from the <br /> unaffected segment of Trout Creek above its confluence with Middle Creek, nullifying <br /> any temporary, minor impacts which could occur. (See TC Life of Mine Application <br /> Map No. 15). <br /> The primary function of the Foidel Creek/Middle Creek Confluence AVF is the <br /> support of flood irrigated hayland. As previously noted, the flood irrigation water is <br /> not diverted from affected segments of either Foidel Creek or Middle Creek, but is <br /> diverted from an unaffected segment of Trout Creek. A field inspection conducted by <br /> the Division in late August of 1986 observed vegetation on the flood irrigated AVF to <br /> be more robust than adjacent areas upstream on Foidel Creek above the Trout Creek <br /> irrigation diversion (assumed to be subirrigated). The flood irrigated pasture was <br /> dominated by pasture grasses while weedy species were visually dominant on the <br /> non-irrigated reach (see vegetation data in supplemental Report of 9/22/86). From <br /> comparison of the adjacent flood irrigated and non-flood irrigated areas, it appears that <br /> sub-irrigation has little impact on the agricultural productivity of the Foidel <br /> Creek/Middle Creek Confluence AVF, and that flood irrigation is the critical function. <br /> Significant increases in the salinity of alluvial ground water in the confluence area <br /> would not be anticipated since the majority of the recharge to the aquifer occurs during <br /> spring and early summer when Middle Creek and Foidel Creek flows are highest and <br /> conductivity levels are lowest. Further dilution of alluvial waters would be provided <br /> by Trout Creek irrigation drainage water. Since Trout Creek irrigation water supports <br /> the critical function of the alluvial valley floor and the Trout Creek waters would not <br /> be affected by the proposed operations, material damage to the quality of water <br /> supplying the Foidel Creek/Middle Creek Confluence AVF would not occur. <br /> 3. The proposed operation will preserve, throughout the mining operation, the essential <br /> hydrologic functions of the alluvial valley floor. <br /> The essential hydrologic functions of the Foidel Creek/Middle Creek Confluence AVF <br /> are flood irrigation primarily and, to a lesser extent, sub-irrigation, and both functions <br /> would be preserved. <br /> Flood irrigation on the Foidel Creek/Middle Creek Confluence AVF is by diversion of <br /> unaffected Trout Creek water. Sub-irrigation does not playa major role in maintaining <br /> the agricultural productivity of the AVF, but the quality of alluvial ground water <br /> would be maintained above the material damage suspect level of 3 mmhos/cm due to <br /> the fact that aquifer recharge occurs primarily in the spring and early summer when <br /> Foidel Creek Mine 46 August 4,2023 <br />