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3. The mining operations have already disturbed much of the alluvial valley Floor within the <br />permit area prior to August 3, 1977, with construction of the overland conveyor and loadout <br />facility. No additional disturbance of this area is planned. The essential hydrologic functions <br />of those areas which will remain undisturbed will be preserved. <br />The permittee will be required to restore the essential hydrologic functions on the entire alluvial <br />valley floor where disturbance has occurred. There are no "grandfathering" provisions for <br />restoring the essential hydrologic functions on an alluvial valley Floor. <br />The permittee identified subirrigation and flood irrigation as the essential hydrologic functions <br />of the AVF. (n the past, the Highline Canal, which is immediately upslope of the AVF, has been <br />the source of water for irrigating a portion of the AVF. No irrigation presently takes place in the <br />site area. Subirrigation is controlled by [he water level in the adjacent Colorado River. <br />Reclamation and restoration of the essential hydrologic functions will involve removing all <br />facilities, regrading to the approximate original river terrace topography, replacing topsoil, and <br />revegetating. A flood irrigation system had apparently been abandoned at some point <br />prior to loadout site development in 1977, and areas designated as historically flood <br />irrigated in and adjacent to the permit area, have not been flood irrigated since that time. <br />The approved postmining land use for the loadout area is wildlife habitat, and the <br />revegetation plan would establish predominantly native vegetation, which would support <br />wildlife habitat. However, the former flood irrigation ditch as depicted on Exhibit 33 will <br />be reestablished and connected to the Highline Canal during final reclamation. <br />Reestablishment of the original topography and replacement of the irrigation ditch will <br />restore the capability for flood irrigation of the acreage identified as "historically flood <br />imgated" on Exhibit 33. <br />The reclamation procedure will also restore the essential hydrologic function of subirrigation. <br />Quantity and quality of water is largely regulated by the Colorado River. Any quality changes <br />resulting from the surface operations will be of short duration due to the close proximity of the <br />Colorado River and the extensive underflow associated with this relatively large surface water <br />Flow system. In addition, if a groundwater problem is detected by the monitoring program, <br />mitigation measures will be undertaken prior to reclamation of the site. <br />In summary, surface coal mining and reclamation operations will be conducted to <br />preserve, throughout the mining and reclamation process, the essential hydrologic <br />functions of the alluvial valley floors not within the permit area, and operations will be <br />conducted to reestablish the essential hydrologic functions of alluvial valley floors within <br />the permit area (4.24.2(1). <br />Rya id/Cottonwood Creek Area <br />Four distinct aeeas were examined for identification of alluvial valley Floors in the vicinity of Rapid <br />Creek and Cottonwood Creek. These areas were Cottonwood Creek, Rapid Creek, minor ephemeral <br />streams and the Colorado River adjacent to the Rapid Creek and Cottonwood Creeks watersheds. <br />None of these areas are covered by the "grandfathering" exemption. <br />49 <br />