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The Big Bottom AVF will not be undermined during this permit term by the No. 5 or <br />No. 6 Mine. Portions of the Big Bottom AVF were previously undermined by the <br />development of mains and sub -mains (partial extraction only) for the No. 5 Mine. <br />Monitoring has shown no impacts to the alluvial valley floor due to previous <br />undermining by the No. 5 Mine. The life -of -mine projection shows proposed <br />undermining by longwall methods of a small portion of the Big Bottom by both the No. <br />5 and No. 6 Mines. The application contains no information on possible impacts to the <br />Big Bottom AVF or on mining methods to be utilized to mitigate such impacts for <br />future extraction under the Big Bottom AVF. For this reason, no future mining under <br />the Yampa or Williams Fork River is being approved with this permit renewal. The <br />Williams Fork Mines operation ceased coal extraction in December 1995 and entered <br />into temporary cessation. No additional underground development or coal extraction <br />has occurred since that time. <br />The now abandoned No. 9 Mine has development entries under the Big Bottom AVF; <br />however, full extraction mining was not conducted. An AVF exemption for this past <br />mining was requested and approved by the Division and OSM. A copy of the AVF <br />exemption request is presented in Exhibit 4, and the extent of the No. 9 Mine workings <br />is shown on the mine plan map, Map 23. No mining is approved for the No. 9 Mine <br />during this five -year permit term. The No. 9 Mine is presently flooding and the operator <br />utilized the portal area for a coal processing waste pile and the portal area has been <br />reclaimed. <br />Subsidence monitoring conducted by the operator has shown no effects to the Big <br />Bottom AVF due to past development mining. The essential hydrologic functions of <br />this AVF have not been affected. <br />Surface coal mining operations conducted within the geographic extent of the area <br />eligible for the exemption are not required to comply with the requirements of Rule <br />2.06.8(5)(a)(i) and (ii). Operations eligible for the exemption, however, are required to <br />restore the essential hydrologic functions of the affected alluvial valley floors by <br />implementing the approved reclamation plan. The Division finds that upon completion <br />of the reclamation plan, the essential hydrologic function of both the Yampa and <br />William Fork alluvial valley floors should be restored. <br />Yampa River Round Bottom Alluvial Valley Floor <br />The approximate extent of the Yampa River alluvium of the Round Bottom area is <br />shown on Map 25 of the permit application. The essential hydrologic function of the <br />Round Bottom alluvial valley floor is its capacity for supporting flood irrigation. Crop <br />production may be augmented by subirrigation; however, subirrigation is considered to <br />be minor. The Round Bottom alluvial valley floor primarily supports flood irrigated <br />hayfields and pasturelands. <br />The No. 9 Mine workings are not in close proximity to, nor do they impact areas <br />tributary to, the Round Bottom AVF. Therefore, no impacts to the essential hydrologic <br />functions of the Round Bottom alluvial valley floor occurred. The No. 5 Mine does not <br />Williams Fork Mines 39 Permit Renewal 06 <br />C- 1981 -044 December 8, 2014 <br />