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The essential hydrologic functions of the Rapid Creek alluvial valley floor are those geologic, hydrologic, topographic, and soil characteristics that give the area the ability to support flood irrigated agricultural activities. Since no mining activities would take place within the AVG, the geologic, topographic, and sail characteristics of the AVF would be unaffected. Rapid Creek and Cottonwood Creeks would be undermined under a limited extraction plan and mining would not effect the surface water system that supplies the alluvial valley floor. Colorado River Alluvial Valley Floor -Findings 1. The proposed surface coal mining operations would not interrupt, discontinue or preclude farming on an alluvial valley floor. The area designated as alluvial valley floor lies outside of the permit area, downstream from the proposed operations. As a result, there would be no surface disturbance within the AVF, and the area would not be undermined. 2. The proposed surface coal mining operations would not materially damage the quantity or quality of water in surface and underground water systems that supply those alluvial valley floors or portions of alluvial valley floors. Water for flood irrigated agricultural activities is obtained from two sources. The upper terrace areas at the mouth of Rapid Creek are irrigated by flow from the Rapid Creek system. As discussed above, mining would not affect either water quality or quantity in the Rapid Creek/Cottonwood Creek stream system. Agricultural activities on the lower terraces and floodplain area are flood irrigated with water derived from the Colorado River. Some of the lower areas may be marginally subirrigated by alluvial ground water. The proposed operation would not affect the quantity of flow in the Colorado River stream/alluvial aquifer system. Disposal of coal refuse material in an adjacent area, and the discharge of mine water from underground workings could affect water quality. The Division has assessed the possible affects of these activities and has not identified any significant change in water quality. 3. Surface coal mining and reclamation operations would be conducted to preserve, throughout the mining and reclamation process, the essential hydrologic functions of the alluvial valley floors. The essential hydrologic functions of the Colorado River alluvial valley floor are those geologic, hydrologic, topographic, and soil characteristics that give the area the ability to support flood irrigated agricultural activities. Subirrigation is a marginal function that is limited to a few of the lower area which are also -25-