2007-07-30_GENERAL DOCUMENTS - C1981041

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i I The reclamation procedure will also restore the essential hydrologic function of subircigation. Quantity and quality of water is largely regulated by the Colorado River. Any quality changes resulting from the surface operations will be of short duration dine to the close proximity of the Colorado River and the extensive underflow associated with this~'relatively large surface water flow system. [n addition, if a groundwater problem is detected, by the monitoring program, mitigation measures will be undertaken prior to reclamation ofthe site. i In summary, surface coal mining and reclamation operations vJill be conducted to preserve, throughout the mining and reclamation process, the essential hydriologic functions ofthe alluvial valley floors not within the permit area, and operations will be~!'iconducted to reestablish the essential hydrologic functions of alluvial valley floors within the~Vpermit area (4.24.2(1). I ~. Rapid/Cottonwood Creek Area Four distinct aeeas were examined for identification of alluvial valley Floors in the vicinity of Rapid Creek and Cottonwood Creek. These aeeas were Cottonwood Creek, Rapid Creek, minor ephemeral streams and the Colorado River adjacent to the Rapid Creek and Cottonwood Creeks watersheds. None of these areas aze covered by the "grandfathering" exemption: ~` The Cottonwood Creek valley does not meet the geomorphic characteriistics ofan alluvial valley floor. The valley is narrow, and any fill material does not meet the AVF sizi; criteria. Valley fill deposits located along Rapid Creek have been interpretedas;a mudflow fan deposit which has been modified and reworked by Rapid Creek to form three terrace b:vels. The upper terraces (T2 and T3) are irrigated or have been irrigated with the flow from Rapid Creek. The lowest terrace (Tl ) is narrow and has not been flood irrigated. The TI terrace includes a narcow band of subircigation along the creek, but the species present are not agriculturally useful. Siibircigated species located on the T2 terrace are deep rooted and do not indicate the general availability of groundwater to agriculturally useful species. The T3 tercace does not have vegetation'indicating subircigation. Several minor ephemeral streams also drain the permit area. The stream,valleys are narcow, steep, and contain very little alluvium. None of these valleys contain deposits mE:eting the AVF size criteria. I Areas along theColorado River have been identified as terrace laridforms with existing flood irrigation. The lowest terrace is marginaNy subircigated, but the upper terraces are not subirrigated. Based on the above information, two areas of alluvial valley floors can be identified. The two upper terraces (T2 and T3) have been identified as unconsolidated streamlaid'deposits, and have sufficient waters to support flood ircigated agicultural activities. (Except, two ofthe areas designated on Map 1 as have been disturbed by previous unrelated mining activities and by construction of water treatment facilities and should not be identified as alluvial valley Floors.) 'The areas designated as CRT (Colorado River Tercace), as well as the lower tercaces and floodplain along the Colorado River, are determined to beialluvial valley Floors. The areas identified as CRT consists of unconsolidated streamlaid deposits that are currently flood ircigated. The lower terra~;es and floodplain are flood ircigated in several areas (Map 2), and may be subirrigated in places. Sigrtificance to Agriculture Permit Revision No. 3 July 30, 2007 Permit No. C-1981-041 Page 56