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system, and no disturbed runoff or mine water would be discharge to Rapid Creek or <br />Cottonwood Creek, the proposed operations will not affect water quality. The Division has <br />estimated that stream Flow depletion in the absence of flow through fractures, either natural or <br />as a result of subsidence, would be less than 0.003 cfs. Such a minor loss would not be <br />detectable. The permittee has proposed a limited extraction mine plan beneath the streams, and <br />subsidence effects would not be expected in these areas. No major natural fractures have been <br />identified in the permit application. Minor fractures are undoubtedly present, but may not be <br />open to the passage of groundwater. The required surface water and mine water monitoring will <br />detect any unanticipated change in Che existing hydrologic system. <br />Surface coal mining and reclamation operations would be conducted [o preserve, throughout the <br />mining and reclamation process, the essential hydrologic functions of the alluvial valley Floor <br />(4.24.2(1). <br />The essential hydrologic functions of the Rapid Creek alluvial valley Floor are those geologic, <br />hydrologic, topographic, and soil characteristics that give the area the ability to support flood <br />irrigated agricultural activities. Since no mining activities would take place within the AVF, the <br />geologic, topographic, and soil characteristics of the AVF would be unaffected. Rapid Creek <br />and Cottonwood Creeks would be undermined under a limited extraction plan and mining would <br />not effect the surface water system that supplies the alluvial valley floor. <br />Colorado River Alluvial Vallev Floor - Findin¢s <br />The proposed surface coal mining operations would not interrupt, discontinue or preclude <br />fanning on an alluvial valley floor that is irrigated or naturally subirtiga[ed. <br />The area designated as alluvial valley floor lies outside of the permit area, downstream from the <br />proposed operations. As a result, there would be no surface disturbance within the AVF, and <br />the area would not be undermined. No irrigation occurs along this stretch of the river where the <br />permit area is located except for undeveloped rangelands which are not significant to farming <br />(4.24.3(1) and 2.06.8(5)(a)(i)). <br />2. The proposed surface coal mining operations would not materially damage the quantity or quality <br />of water in surface and undergroundwater systems that supply those alluvial valley floors or <br />portions of alluvial valley floors (4.24.3(3) and 2.06.8(5)(a)(ii)). <br />Wazer for flood irrigated agricultural activities is obtained from two sources. The upper terrace <br />areas at the mouth of Rapid Creek are irtigated by Flow from the Rapid Creek system. As <br />discussed above, mining would not affect either water quality or quantity in the Rapid <br />Creek/Cottonwood Creek stream system. <br />Agricultural activities on the lower tertaces and floodplain area are flood irrigated with water <br />derived from the Colorado River. Some of the lower areas may be marginally subirtigated by <br />alluvial groundwater. The proposed operation would not affect the quantity of Flow in the <br />Colorado River stream alluvial aquifer system. Disposal of coal refuse material in an adjacent <br />area, and the discharge of mine water from underground workings could affect water quality. <br />The Division has assessed the possible affects of these activities and has not identified any <br />51 <br />