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Areas along the Colorado River have been identified as terrace landforms with existing flood <br />irrigation. The lowest terrace is marginally subirrigated, but the upper terraces are not subirrigated. <br />Based on the above information, two areas of alluvial valley floors can be identified. The two upper <br />terraces (T2 and T3) have been identified as unconsolidated streamlaid deposits, and have sufficient <br />waters to support flood irrigated agricultural activities. (Except, two of the areas designated on Map 1 <br />as have been disturbed by previous unrelated mining activities and by construction of water treatment <br />facilities and should not be identified as alluvial valley floors.) The areas designated as CRT <br />(Colorado River Terrace), as well as the lower terraces and floodplain along the Colorado River, are <br />determined to be alluvial valley floors. The areas identified as CRT consists of unconsolidated <br />streamlaid deposits that are currently flood irrigated. The lower terraces and floodplain are flood <br />irrigated in several areas (Map 2), and may be subirrigated in places. <br />Significance to Agriculture <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 - Findings <br />The proposed surface coal mining operations would not interrupt, discontinue, or preclude <br />farming on an alluvial valley floor (4.24.3(l)). <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 the <br />area 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 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 as <br />a result of subsidence, would be less than 0.003 cfs. Such a minor loss would not be detectable. <br />The permittee has proposed a limited extraction mine plan beneath the streams, and subsidence <br />effects would not be expected in these areas. 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 />Permit Revision No. 4 55 February 3, 2009