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Based on the above discussion, the Division finds that the proposed <br /> operations will not materially damage the quantity and quality of <br /> water in the surface and underground water systems that supply the <br /> alluvial valley floor or portions of the alluvial valley floor. <br /> 3. The mining operations have already disturbed much of the alluvial <br /> valley floor under Permit No. 77-442 , with construction of the <br /> overland conveyor and loadout facility. No additional disturbance <br /> of this area is planned. The essential hydrologic functions of <br /> those areas which will remain undisturbed will be preserved. <br /> The permittee will be required to restore the essential hydrologic <br /> functions on the entire alluvial valley floor where disturbance has <br /> occurred. There are no "grandfathering" provisions for restoring <br /> the essential hydrologic functions on an alluvial valley floor . <br /> The permittee identified subirrigation and flood irrigation as the <br /> essential hydrologic functions of the AVF. In the past, the <br /> Highline Canal , which is immediately upslope of the AVF, has been <br /> the source of water for irrigating a portion of the AVF. No <br /> irrigation presently takes place in the site area. Subirrigation <br /> is controlled by the water level in the adjacent Colorado River . <br /> Reclamation and restoration of the essential hydrologic functions <br /> will involve removing all facilities , regrading to the approximate <br /> original river terrace topography, replacing topsoil , and <br /> revegetating. A flood irrigation system will be reestablished and <br /> the system will be connected to the Highline Canal . This will <br /> provide for restoration of the essential hydrologic function of <br /> flood irrigation. <br /> The reclamation procedure should also restore the essential <br /> hydrologic function of subirrigation. Quantity and quality of <br /> water is largely regulated by the Colorado River. Any quality <br /> changes resulting from the surface operations will be of short <br /> duration due to the close proximity of the Colorado River and the <br /> extensive underflow associated with this relatively large surface <br /> water flow system. In addition, if a ground water problem is <br /> detected by the monitoring program, mitigation measures will be <br /> undertaken prior to reclamation of the site . <br /> Rapid/Cottonwood Creek Area <br /> Four distinct areas were examined for identification of alluvial valley <br /> floors in the vicinity of Rapid Creek and Cottonwood Creek. These <br /> areas were Cottonwood Creek, Rapid Creek, minor ephemeral streams and <br /> the Colorado River adjacent to the Rapid Creek and Cottonwood Creeks <br /> watersheds . None of these areas are covered by the "grandfathering" <br /> exemption. <br /> The Cottonwood Creek valley does not meet the geomorphic <br /> characteristics of an alluvial valley floor . The valley is narrow, and <br /> any fill material does not meet the AVF size criteria . <br /> -42- <br />