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2010-05-07_GENERAL DOCUMENTS - C1982057
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2010-05-07_GENERAL DOCUMENTS - C1982057
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Last modified
8/24/2016 4:11:36 PM
Creation date
5/11/2010 1:40:37 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1982057
IBM Index Class Name
General Documents
Doc Date
5/7/2010
Doc Name
Proposed Decision & Findings of Compliance for SL2
From
Phase I
Permit Index Doc Type
Findings
Email Name
DTM
SB1
Media Type
D
Archive
No
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Background <br />The Seneca II-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 4093.0 <br />acres. <br />Elevations at the mine site range from 6400 to 8350 feet above mean sea level. Slopes range from <br />about 2 percent to nearly 100 percent. Prominent ledges are formed by the Twentymile sandstone in <br />the western permit area and the Trout Creek sandstone ledge in the eastern permit boundary. Many <br />of the drainages are deeply incised. <br />The mine permit boundary encompasses two surface watersheds as seen in Figure 2 of this document. <br />Most of the mine site and the major portion of the reclaimed area drain into the Dry Creek watershed <br />from Hubberson Gulch and an unnamed tributary to Dry Creek. A small area on the eastern edge of <br />the permit boundary drains to Sage Creek. Dry Creek and Sage Creek are perennial tributaries to the <br />Yampa River. The Yampa 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 of <br />difficult mining conditions and economic factors. Seneca II-W was a dip-slope area strip mine <br />operation, which utilized dragline mining methods primarily, with limited auger mining in some final <br />pit locations. During active mining operations, the coal from the Seneca II-W Mine was hauled over <br />County Road 53 and the Tie-Across Haul Road by a private hauler to the Hayden Station Power <br />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, topsoil <br />replacement, and revegetation. During the period of active operations, reclamation was conducted <br />concurrently with mining. Using the dragline, initial box cut spoil was placed onto previously <br />stripped but unmined ground creating a temporary overburden stockpile with each successive cut <br />going into the previous pit after coal was removed. The resulting spoils were graded to approximate <br />original contour, topsoiled and seeded. Permanent postmine drainage channels were constructed to <br />resemble pre-mining conditions. <br />The mining portion of the permit area was comprised of two primary units, the "Original" permit area <br />and the "South Extension" area, which was added to the original permit area to allow for additional <br />coal extraction. The area of coal extraction within the original permit area was a dip-slope land form, <br />in which the land surface was a broad expanse of long, relatively gradual slopes that rise from west to <br />east, broken up by a number of ephemeral drainages that flow to the west into Dry Creek or its <br />tributary Hubberson Gulch. The eastern boundary of the mining area was defined by a north/south <br />trending ridgeline that drops abruptly off to the east, into steep sided tributaries of Sage Creek. <br />Within the original permit area, Mine Pits A, B, C, and D were oriented perpendicular to the cropline <br />and the coal in the mine pit area dipped approximately 18 to 25%. A single dragline operated <br />alternately within the north (Pits C and D) and south areas (Pits A and B). The Wadge coal seam was <br />mined in all four pits from the cropline to approximately 100 feet in depth. Auger mining was <br />conducted within certain final pit locations in the original permit area. Mining in the south extension <br />4
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