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Originally, the AVF determination was required in order to demonstrate a <br />proposed coal mine waste pile would not be located in an AVF. However, <br />a coal mine waste pile is no longer proposed for that area delineated in <br />Appendix W. The Operator will incorporate the AVF study and DRMS' <br />AVF determination into Appendix W. <br />A thorough investigation of the area south of the McClane Canyon Mine <br />surface facilities has been deemed adequate in accordance with Rule <br />2.06.08(3). There is an appropriate combination of studies concluding a <br />negative AVF determination by the Division. <br />Nearly 95 percent of the investigation area is covered by various deposits <br />that resulted from unconsolidated runoff or slope wash, talus, and <br />landslide deposits. Therefore, Rules 2.06.8(3)(c)(ii)( A and C) are met. <br />The two areas with exposed older alluvium total slightly more than one <br />acre which is considerably smaller than the smallest currently cultivated <br />parcel along East Salt Creek (9.1 acres). Therefore, these alluvial areas <br />do not meet the regional practices criterion, as required by Rule <br />2.06.8(3)(c)(ii)(B). <br />The AVF investigation site geology indicates that East Salt Creek <br />developed a relatively wide floodplain, depositing more than 20 feet of <br />alluvium in the geologic past. Fans from side canyons and colluvial <br />deposits probably existed at the time, but the creek was active enough to <br />maintain a wider floodplain, eroding and removing other deposits. At some <br />time in the past, the creek downcut through the older alluvium becoming <br />entrenched, limiting its ability to maintain the wider floodplain. The <br />floodplain was subsequently encroached upon by deposits from the <br />canyon walls (colluvium) and fans from side canyons or small drainages. <br />A water diversion system was constructed in the late 1800s at the <br />constriction of East Salt Creek (see Geology section of AVF report for <br />more detail). The purpose of the structure was to divert water from East <br />Salt Creek to a ditch that originated below the structure. The ditch was <br />installed to provide water for growing oats on fields located lower in the <br />valley, but the ditch never operated because sediment filled the diversion <br />structure during the first spring. After that event, the builders abandoned <br />PR -02 2.06-2 10/12 <br />