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Given the fact that Foidel Creek has peen conve^"ed from a~ intermittent ±o a perennial stream as a result of underground mine water and spoil aquiFer discharge, and the fact that i4iddle Creek would be neither undermined nor diverted by the proposed operations, there is no possibility of diminution of the quantity of water supplying the alluvial valley floor. Further, the entire alluvial valley floor is flood irrigated by water diverted from the unaffected segment of Trout Creek above its confluence with Middle Creek (See TCC Life-of-Mine Application Map No. 15). The primary function of the confluence AVF is the support of flood irrigated hayland. As previously noted, the flood irrigation water is not diverted from affected segments of either Foidel Creek or Middle Creek, but is diverted from an unaffected segment of Trout Creek. Afield inspection conducted by the Division in late August of 1986 revealed vegetation on the flood irrigated AVF to be more productive than adjacent areas upstream on Foidel Creek above the Trout Creek irrigation diversion (assumed to be sub-irrigated). The flood irrigated pasture was dominated by pasture grasses while weedy species were visually dominant on the non-irrigated reach (see vegetation data in TCC Exhibit 43). From comparison of the adjacent flood irrigated and non-flood irrigated areas it appears that sub-irrigation has little impact on the agricultural productivity of the confluence AVF, and that flood irrigation is the critica] function. Significant ':~cr~•_ses in the salinity of alluvial ground water in the confluence area would not be anticipated since the majority of the recharge to the aquifer occurs during spring and early summer when Middle Creek and Foidel Creek flows are highest and conductivity levels are ]owest. Further dilution of alluvial waters would be provided by Trout Creek irrigation drainage water. Since Trout Creek irrigation water supports the critical function of the alluvial valley floor and the Trout Creek waters would not be affected by the proposed operations, material damage to the quality of water supplying the AYF would not occur. 3. The proposed operation would preserve, throughout the mining operation, the essential hydrologic functions of the alluvial valley floor. The essential hydrologic functions of the confluence AVF are flood irrigation primarily and, to a lesser extent, sub-irrigation, and both functions would be preserved. As discussed previously the AVF is outside the proposed pemit area and would not be directly affected by mining. Flood irrigation on the AVF is by diversion of Trout Creek water which would not be affected by the proposed operations. Sub-irrigation does not play a major role in maintaining the agricultural productivity of the AVF, but the quality of alluvial ground water would be maintained above the material damage suspect level of 3 mmhos/cm due to the fact that aquifer recharge occurs primarily in the spring and early summer when stream salinity levels are lowest, and the alluvial water would be further diluted by the low salinity Trout Creek irrigation drainage water. Upper Middle Creek Map 6 of the original C-81-071 permit document identifies two separate alluvial bodies located several miles upstream from the Foidel Creek/i4iddle 27