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Valley fill deposits located along Rapid Creek have been interpreted as a mudflow fan deposit which has <br />been modified and reworked by Rapid Creek to form three terrace levels. The upper terraces (T2 and <br />T3) are irrigated or have been irrigated with the flow from Rapid Creek. The lowest terrace (T1) is <br />narrow and has not been flood irrigated. The T 1 terrace includes a narrow band of subirrigation along <br />the creek, but the species present are not agriculturally useful. Subirrigated species located on the T2 <br />terrace are deep rooted and do not indicate the general availability of groundwater to agriculturally useful <br />species. The T3 terrace does not have vegetation indicating subirrigation. <br />Several minor ephemeral streams also drain the permit area. The stream valleys are narrow, steep, and <br />contain very little alluvium. None of these valleys contain deposits meeting the AVF size criteria. <br />Areas along the Colorado River have been identified as terrace landforms with existing flood irrigation <br />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 as <br />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 (Colorado <br />River Terrace), as well as the lower terraces and floodplain along the Colorado River, are determined to <br />be alluvial valley floors. The areas identified as CRT consists of unconsolidated streamlaid deposits that <br />are currently flood irrigated. The lower terraces and floodplain are flood irrigated in several areas (Map <br />2), and may be 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 - Findings <br />The proposed surface coal mining operations would not interrupt, discontinue, or preclude farming <br />on an alluvial valley floor (4.24.3(1)). <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 quality <br />of water in surface and groundwater systems that supply these alluvial valley floors or portions of <br />alluvial valley floors (4.24.3(3)). <br />The Rapid Creek alluvial valley floor receives the water supply from the Rapid Creek/Cottonwood <br />Creek stream system. Since no surface facilities are located within this system, and no disturbed <br />runoff or mine water would be discharge to Rapid Creek or Cottonwood Creek, the proposed <br />operations will not affect water quality. The Division has estimated that stream flow depletion in <br />the absence of flow through fractures, either natural or as a result of subsidence, would be less than <br />55 <br />