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Background <br />The Seneca 11-W Mine is located in northwest Colorado, approximately seven miles south of the <br />town of Hayden in Routt County off County Road 53. The total permit area encompasses <br />3,878.50 acres. <br />Elevations at the mine site range from 6400 to 8350 feet above mean sea level. Slopes range <br />from about 2 percent to nearly 100 percent. Prominent ledges are formed by the Twentymile <br />sandstone in the western permit area and the Trout Creek sandstone ledge in the eastern permit <br />boundary. Many of the drainages are deeply incised. <br />The mine permit boundary encompasses two surface watersheds. The major portion of the <br />reclaimed area drains into the Dry Creek watershed from Hubberson Gulch and an unnamed <br />tributary to Dry Creek. A small area on the eastern edge of the permit boundary drains to Sage <br />Creek. Dry Creek and Sage Creek are perennial tributaries to the Yampa River. The Yampa <br />River then flows to the Green River and eventually the Colorado River. <br />Coal extraction began at Seneca II -W in 1990, and ceased in January 2006 due to a combination <br />of difficult mining conditions and economic factors. Seneca II -W was a dip -slope area strip <br />mine operation, which utilized dragline mining methods primarily, with limited auger mining in <br />some final pit locations. During active mining operations, the coal from the Seneca II -W Mine <br />was hauled over County Road 53 and the Tie - Across Haul Road by a private hauler to the <br />Hayden Station Power Plant. Haulage distance was approximately 10 miles each way. <br />Area strip mining techniques used at the mine included vegetation removal, topsoil stripping, <br />fragmentation and removal of overburden, fragmentation and removal of coal, spoils grading, <br />topsoil replacement, and revegetation. During the period of active operations, reclamation was <br />conducted concurrently with mining. Using the dragline, initial box cut spoil was placed onto <br />previously stripped but unmined ground creating a temporary overburden stockpile with each <br />successive cut going into the previous pit after coal was removed. The resulting spoils were <br />graded to approximate original contour, topsoiled and seeded. Permanent post -mine drainage <br />channels were constructed to resemble pre- mining conditions. <br />The mining portion of the permit area was comprised of two primary units, the "Original" permit <br />area and the "South Extension Area ", which was added to the original permit area to allow for <br />additional coal extraction. The area of coal extraction within the original permit area was a dip - <br />slope land form, in which the land surface was a broad expanse of long, relatively gradual slopes <br />that rise from west to east, broken up by a number of ephemeral drainages that flow to the west <br />into Dry Creek or its tributary Hubberson Gulch. The eastern boundary of the mining area was <br />defined by a north/south trending ridgeline that drops abruptly off to the east, into steep sided <br />tributaries of Sage Creek. Within the original permit area, Mine Pits A, B, C, and D were <br />oriented perpendicular to the cropline, and the coal in the mine pit area dipped approximately 18 <br />to 25 %. A single dragline operated alternately within the north (Pits C and D) and south areas <br />(Pits A and B). The Wadge coal seam was mined in all four pits from the cropline to <br />approximately 100 feet in depth. Auger mining was conducted within certain final pit locations <br />Page 6 of 18 <br />