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XVII. Operations on Alluvial Valley Floors Two areas were identified within or adjacent to the mine that met the geomorphic criteria of alluvial valley floors. Deposits of unconsolidated alluvial materials were identified along Mann Draw and at the confluence of Mann Draw and the Canadian River. However, only the alluvium of the Canadian River located l.7 mile below the mine site, met the hydrologic criteria for an alluvial valley floor. In Mann Draw, there is insufficient water to support agricultural activities. The stream channel of the draw is small and discontinuous in many Sections. There is no existing or historic flood irrigation in the draw. A regional flood irrigation study was conducted in North Pazk [o assess whether flood irrigation was feasible. Both the Canadian and Michigan Rivers and their tributaries were considered in the study (Plate 22 of the permit application). The results of the study show that irrigated watersheds in the region generally flow towazd the southwest and have maximum basin elevations from 10,880 to 12,560 feet. Mann Draw is oriented northeast and has a maximum elevation of 8,340 feet. The higher elevated watersheds receive greater than 25 inches of annual precipitation, while Mann Draw receives approximately 10 inches of precipitation annually. Little evidence of subirrigation in Mann Draw was found in the study. Areas where the vegetation suggests subirrigation are discontinuous and limited to narrow bands along the channel ways. The Division has reviewed the alluvial valley floor study prepazed by Leonazd Rice Consulting Water Engineers and included in Appendix I of the application. Based on evidence supplied by the applicant, the Division finds that Mann Draw is not alluvial valley floor. The only area identified as an alluvial valley floor is the Canadian River, which is both flood irrigated and subirrigated. This river is located 1.7 miles downstream from the mine site. Alluvial Valley Floors -Canadian River -Findings The proposed surface coal mining operations would not interrupt, discontinue, or preclude farming on an alluvia] valley floor. The permit azea is located 1.7 miles from the alluvial valley floor and would no[ physically affect farming activities. 2. The proposed surface coal mining operations would not materially damage the quantity and quality of water in surface and groundwater systems that supply those alluvial valley floors or portions of alluvial valley floors. Bourg Strip Mine. C-81-021 27 August 4, 1998