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during this five-yeaz 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 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 fmds 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 Palley Floor <br />The approximate extent of the Yampa River alluvium of the Round Bottom azea 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, subin•igation is considered to <br />be minor. The Round Bottom alluvial valley floor primarily supports flood imgated <br />hayfields and pasturelands. <br />The Eagle 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 Eagle No. 5 Mine <br />does not extend under the Round Bottom alluvial valley floor. The 2 West workings of <br />this mine did, however, undermine approximately 90 acres containing surface and <br />ground waters tributary to the Round Bottom alluvial valley floor. The 2 West workings <br />undermined small ephemeral streams directly tributary to the Yampa River/Round <br />Bottom alluvial valley floor. The 2 West workings also undermined the Twentymile <br />and Middle Sandstone aquifers along the upper edge of the Round Bottom Synclinal <br />Basin (a regional ground water basin) and along the axis of the Williams Fork Anticline. <br />The 2 W workings have been abandoned for more than ten years. Only minor areas had <br />pillars pulled. Other mining was development by room and pillaring only. The impacts <br />to the quantity of water supplied to the Round Bottom AVF were previously (in the <br />l 984 Findings Document) predicted to be negligible upon evaluating the proposed mine <br />plan. Due to the reduced azeas of mining, impacts are considered to be negligible for <br />both quality and quantity of water supplied to the Big Bottom AVF. <br />The Eagle No. 5 Mine will not disrupt the essential hydrologic functions (e.g., the <br />capacity for flood irrigation) of the Round Bottom alluvial valley floor. The mine will <br />neither undermine the land surface of the alluvial valley floor nor undermine the <br />irrigation systems supplying the alluvial valley floor. Therefore, there will be no <br />37 <br />