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facilities and should not be identified as alluvial valley floors.) The azeas designated as CRT <br />(Colorado River Terrace), as well as the lower terraces and floodplain along the Colorado River, aze <br />determined to be alluvial valley floors. The azeas identified as CRT consists of unconsolidated <br />stteamlaid deposits that aze currently flood irrigated. The lower terraces and floodplain are flood <br />irrigated in several azeas (Map 2), and maybe subirrigated in places. <br />Sienificance to Aericulture <br />Since no agricultural information has been provided from any of the areas designated as alluvial valley <br />floors, all the areas will be assumed to be agriculturally significant, and all three alluvial valley floor <br />findings will be made. <br />Rapid Creek Alluvial Valley Floor - Findines <br />The proposed surface coal mining operations would not interrupt, discontinue, or preclude <br />farming on an alluvial valley floor (4.24.3(1)). <br />The azea 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 the <br />azea would not be undermined. <br />2. The proposed surface coal mining operations would not materially damage the quantity and <br />quality of water in surface and undergroundwater systems that supply these alluvial valley floors <br />or portions of alluvial valley floors (4.24.3(3)). <br />The Rapid Creek alluvial valley floor receives the water supply from the Rapid <br />Creek/Cottonwood Creek stream system. Since no surface facilities are located within this <br />system, and no disturbed runoff or mine water would be dischazge 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 as <br />a result of subsidence, would be less than 0.003 cfs. Such a minor loss would not be detectable. <br />The pertnittee has proposed a limited extraction mine plan beneath the streams, and subsidence <br />effects would not be expected in these azeas. No major natural fractures have been identified in <br />the permit application. Minor fractures are undoubtedly present, but may not be open to the <br />passage of groundwater. The required surface water and mine water monitoring will detect any <br />unanticipated change in the existing hydrologic system. <br />3. Surface coal mining and reclamation operations would be conducted to 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 />imgated agricultural activities. Since no mining activities would take place within the AVF, the <br />geologic, topographic, and soil chazacteristics 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 />52 <br />