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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 play a 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 />stream salinity levels are lowest, and the alluvial water would be further diluted by the <br />low salinity Trout Creek irrigation drainage water. <br />Foidel Creek Mine 50 February 25, 2016 <br />