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August 1976 (Exhibit M of the November 1980 Alluvial Valley Floor Exemption <br />request). <br />Surface coal mining operations conducted within the geographic extent of the azea <br />eligible for the exemption aze 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 affected alluvial valley floors as a part of <br />the reclamation plan. <br />Williams Fork Alluvial Va1leyFloor <br />The approximate boundary of the Williams Fork Alluvial Valley Floor is shown on Map <br />25 of the permit application. Presently, a local farmer hays the field to the north and <br />south of the Eagle No. 5 and 6 surface mine facilities. To the south of the mine facilities <br />is a hayfield east of the railroad tracks. To the north of the mine, there aze hayfields <br />surrounding the train scale and pazalleling the railroad track spur. These hayfields aze <br />flood irrigated by the farmer and RAG Empire. The Worthington Ditch (owned by <br />RAG Empire) provides water to the hayfields. The essential hydrologic function of this <br />alluvial valley floor is the capacity for flood irrigation, coinciding with the regional <br />practice. Subirrigation may also occur, but it is considered secondary to flood irrigation. <br />The No. 5 Mine and associated facilities were established on the Williams Fork River <br />valley floor during the eazly 1970s. Mine entries were developed into the F coal seam, <br />which outcropped above the valley floor. All surface facilities were constructed near the <br />portal entries on the valley floor. The No. 5 and 6 Mines utilize the original portal <br />entries and surface facilities as well as the surface facilities added to the Empire Energy <br />operation during 1981 and 1982. The No. 5 Mine mains extend across the Williams <br />Fork alluvial valley floor. The mains of the No. 6 Mina, which aze developed in the <br />underlying E Seam, will directly underlie the No. 5 Mine mains. Subsidence monitoring <br />to date has shown no impacts to the alluvial valley floor due to the development mining <br />underneath the Williams Fork alluvial valley floor. <br />Technical Revision No. 19 was submitted May 6, 1991, proposing to conduct extraction <br />mining beneath the Williams Fork alluvial valley floor and State Highway 13. The <br />Division approved construction of development mains only and additional subsidence <br />monitoring along Highway 13. <br />Upon cessation of mining, the pumps which drain the mine of water will be shut off and <br />the mine workings allowed to fill. In the Probable Hydroiogic Consequences section of <br />the permit application, the applicant has projected impacts that could occur to the <br />Williams Fork alluvial water quality due to seepage from the flooded mine workings <br />into the Williams Fork alluvium. This scenario assumes that the coal seams are in direct <br />hydrologic communication with the alluvium of the Williams Fork River. Upon <br />flooding of the mines, a head is expected to occur which would allow rechazge of the <br />alluvium by the mine water. The mine water presently pumped from the No. 5 Mine is <br />high in sodium content. Using Darcy's Law, the applicant has projected a net impact of <br />the seepage into the alluvial valley floor to increase the SAR level from 1.9 to 5.2. <br />35 <br />