2023-12-26_GENERAL DOCUMENTS - C1981044

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Page 26 of 27 Surface coal mining operations conducted within the geographic extent of the area eligible for the exemption are not required to comply with the requirements of Rule 2.06.8(5)(a)(1) and(ii). Operations eligible for the exemption,however,are required to restore the essential hydrologic functions of the affected alluvial valley floors by implementing the approved reclamation plan. The Division finds that upon completion of the reclamation plan,the essential hydrologic function of both the Yampa and William Fork alluvial valley floors should be restored. Yampa River Round Bottom Alluvial Valley Floor The approximate extent of the Yampa River alluvium of the Round Bottom area is shown on Map 25 of the permit application. The essential hydrologic function of the Round Bottom alluvial valley floor is its capacity for supporting flood irrigation. Crop production may be augmented by subirrigation;however, subirrigation is a minor resource. The Round Bottom alluvial valley floor primarily supports flood irrigated hayfields and pasturelands. The No. 9 Mine workings are not proximal to,nor do they impact areas tributary to,the Round Bottom AVE Therefore,no impacts to the essential hydrologic functions of the Round Bottom alluvial valley floor occurred. The No. 5 Mine does not extend under the Round Bottom alluvial valley floor. The 2 West workings of this mine did,however,undermine approximately 90 acres containing surface and ground waters tributary to the Round Bottom alluvial valley floor. The 2 West workings undermined small ephemeral streams directly tributary to the Yampa River/Round Bottom alluvial valley floor. The 2 West workings also undermined the Twentymile and Middle Sandstone aquifers along the upper edge of the Round Bottom Synclinal Basin(a regional ground water basin) and along the axis of the Williams Fork Anticline. The 2 West workings have been abandoned for more than ten years. Only minor areas had pillars pulled. Other mining was development by room and pillaring only. The impacts to the quantity of water supplied to the Round Bottom AVF were previously(in the 1984 Findings Document)predicted to be negligible upon evaluating the proposed mine plan. Due to the reduced areas of mining,impacts are considered to be negligible for both quality and quantity of water supplied to the Big Bottom AVE The Division finds that Williams Fork Mines will not impact the essential hydrologic functions of the Yampa River/Round Bottom alluvial valley floor and will not impact the quantity and quality of water supplied to this alluvial valley floor so as to reduce the productivity of the alluvial valley floor. A. The Division has determined that three alluvial valley floors exist within the affected or adjacent area. Therefore,the following findings are for the alluvial valley floors known as Williams Fork alluvial valley floor,Yampa River/Big Bottom alluvial valley floor, and Yampa River/Round Bottom alluvial valley floor. Map 25 of the permit depicts the locations of these resources. The Division finds that activities proposed by the applicant will not interrupt, discontinue,or preclude farming on the alluvial valley floors that are irrigated or naturally subirrigated(4.24.3(l)). The proposed activities will not materially damage the quantity or quality of water in the surface or Williams Fork Mines Prepared by: R ReiRey M.S. GISP C1981044 December 2023