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<br /> <br />two alluvial valley floors (f1VF's) along the Yampa River; the Big Bottom and the <br />Round Bottom alluvial valley floors. Each of these alluvial valley doors are discussed <br />separately, along with the potential impacts of mining. <br />Yampn River Big Bottom A1Gtvinl Valley Floor <br />The approximate boundary of the Big Bottom AVF is shown on Map 25 of the permit <br />application. Hayfields and pastureland are located in the Big Bottom (AVF) azea and <br />are flood irrigated. <br />The Big Bottom AVF will not be undermined during this permit term by the Eagle No. 5 <br />or 6 Mine. Portions of the Big Bottom AVF were previously undermined by the Eagle <br />No. 5 Mine. Monitoring has shown no impacts to the alluvial v,illey floor due to <br />previous undermining by the No. 5 Mine. The life-of-mine projection shows <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 future <br />extraction under the Big Bottom AVF. For this reason, the perntit approval is for the <br />five-year mine plan only of the Eagle No. 5 and 6 Mines. <br />The now abandoned Eagle No. 9 Mine has development entries under the Big Bottom <br />AVF; however, full extraction mining was not conducted. An AVF exemption for this <br />past mining was requested and approved by the Division and O:iM. A copy of the AVF <br />exemption request is presented in Exhibit 4, and the extent of ttie 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 />is utilizing the portal area for a coal processing waste pile. <br />Subsidence monitoring conducted by the operator has shown no effects to the Big <br />Bottom AVF due to past development mining. The essential h}~drologic 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 no[ required to comply with the requirements of Rule <br />2.06.8(5)(a)(i) and (ii). Operations eligible for the exemption, however, aze 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 [he reclamation plan, [he essential hydrologic function of bosh the Yampa and <br />William Fork alluvial valley floors should be restored. <br />Ynmpa River Round Bottom Alluvinl 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 />37 <br />