2022-11-07_REVISION - C1981041 (2)

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Creek/Cottonwood Creek stream system. Since no surface facilities are located within this system,and no disturbed runoff or mine water would be discharge to Rapid Creek or Cottonwood Creek, the proposed operations will not affect water quality. The Division has estimated that stream flow depletion in the absence of flow through fractures, either natural or as a result of subsidence, would be less than 0.003 cfs. Such a minor loss would not be detectable. The permittee has proposed a limited extraction mine plan beneath the streams, and subsidence effects would not be expected in these areas. No major natural fractures have been identified in the permit application. Minor fractures are undoubtedly present, but may not be open to the passage of groundwater. The required surface water and mine water monitoring will detect any unanticipated change in the existing hydrologic system. 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 floor(4.24.2(l)). 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 AVF, the geologic, topographic, and soil characteristics of the AVF would be unaffected. Rapid Creek and Cottonwood Creeks would be undermined under a limited extraction plan and mining would not affect 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 that is irrigated or naturally subirrigated. 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. No irrigation occurs along this stretch of the river where the permit area is located except for undeveloped rangelands which are not significant to farming (4.24.3(1) and 2.06.8(5)(a)(i)). 2. The proposed surface coal mining operations would not materially damage the quantity or quality of water in surface and groundwater systems that supply those alluvial valley floors or portions of alluvial valley floors (4.24.3(3) and 2.06.8(5)(a)(ii)). 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. 66