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-zz- <br />_. <br />Alluvial Valley Floor - Findings (cont'd) <br />with the flow from Rapid Creek. The Lowest terrace (TI) is narrow and has not been <br />flood irrigated. The Tl terrace includes a narrow land of subirrigation along the <br />creek, but the species present are not agriculturally useful. Subirrigated species <br />located on the TZ terrace are deep rooted and do not indicate the general availability <br />of ground water to agriculturally useful species. The T3 terrace does not have <br />vegetation indicating subirrigation. <br />Several minor ephemeral streams also drain the permit area. The stream valleys are <br />narrow, steep, and contain very little alluvium. None of these valleys contain <br />deposits meeting the AVF size criteria. <br />Areas along the Colorado River have been identified as terrace landforms with <br />existing flood irrigation. The lowest terrace is marginally subirrigated, but the <br />upper terraces are not subirrigated. <br />Based on the above information, two areas of alluvial valley floors can be identified_ <br />The two upper terraces (TZ and T3) have been identified as unconsolidated streamlaid <br />deposits, and have sufficient waters to support flood irrigated agricultural activities. <br />(Except, two of the areas designated on Map 1 as have been disturbed by previousunrelated <br />mining activities and by construction of water treatment facilities and should not be <br />identified as alluvial valley floors.) The areas designated as CRT (Colorado River <br />Terrace), as well as, the lower terraces and floodplain along the Colorado River, <br />are determine to be alluvial valley floors. The areas identified as CRT consists of <br />unconsolidated streamlaid deposits that are currently flood irrigated. The lower <br />terraces and floodplain are flood irrigated in several areas (Map 2), and may be <br />subirrigated in places. <br />Significance to Agriculture <br />Since no agricultural information has been provided for any of the areas designated <br />as alluvial valley floors, all the areas will be assumed to be agriculturally <br />significant, and all three alluvial valley floor findings will be made. <br />Rapid Creek Alluvial Va11eu Floor - Findings <br />1. The proposed surface coal mining operations would not interrupt,discrontinue, <br />or preclude farming on an alluvial valley floor. <br />The area designated as alluvial valley floor lies outside of the permit area, down- <br />stream from the proposed operations. As a result, there would be no surface <br />disturbance within the AVF, and the area would not be undermined. <br />2. The proposed surface coal mining operations would not materially damage the <br />quantity and quality of water in surface and underground water systems that supply <br />these alluvial valley floors or portions of alluvial va11y floors. <br />The Rapid Creek alluvial valley floor receives the water supply from the Rapid Creek/ <br />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 <br />has estimated that stream flow depletion in the absence of flow through-fractures, <br />either natural or as a result of subsidence, would be less than 0.003 cfs. Such a <br />minor Zoss would not be detectable. The applicant has proposed a limited extraction <br />mine plan beneath the streams, and subsidence effects would not be expected in <br />these areas. No major natural fractures have been identified in the permit application. <br />Minor fractures are undoubtedly present, but may not be open to the passage <br />