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The proposed mining operations would not cause material damage to the quantity or quality of surface and ground water that supply the alluvial valley floor. As discussed in the PHC Section of this document, significant dewatering of the Foidel Creek stream/alluvial system due to undermining would be precluded by the low vertical permeabilities between the Wadge seam and the alluvium. Any inflow would be more than compensated by the projected mine discharge to Foidel Creek averaging 100 gpm. In fact, existing mine discharge combined with flow from springs emanating from Eckman Park and Mine 1 backfill spoils hoe converted Foidel Creek from an intermittent into a perennial stream. As discussed in the subsidence section of this document, limited extraction mining beneath Foidel Creek would preclude subsidence induced inflows. Given the above considerations, and the fact that Middle 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. A field 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 subirrigated). The flood irrigated pasture was dominated by pasture grasses while weedy species were visually dominant on the non-irrigated reach (see vegetation data in supplemental Report of 9/22/86). From comparison of the adjacent flood irrigated and non-flood irrigated areas it appears that subirrigation has little impact on the agricultural productivity of the confluence AVF, and that flood irrigation is the critical function. Significant increases 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 lowest. 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 AVF would not occur. 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, subirrigation, and both functions would be preserved. As discussed previously the AVF is outside the proposed permit area and would not be directly affected by mining. Flood irrigation on the AVF ie by diversion of unaffected Trout Creek water. Subirrigation 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 27