1996-01-11_REPORT - C1981041 ‎(2)‎

• Permit No: C1981041
• IBM Index Class Name: Report
• Doc Date: 1/11/1996
• Doc Name: Subsidence Monitoring Report
• From: Powderhorn Coal Company
• To: DMG
• Annual Report Year: 1995
• Permit Index Doc Type: Subsidence Report
• Email Name: DIH
• Email Name: JRS
• Media Type: D
• Archive: No

Introduction
This report has been prepared for the Colorado Department of Mining and Geology, DMG,
in response to Stipulation 12 of Powderhorn Coal Company's, PNCC, Mining and Reclamation
Permit No. C - 81 - 041. This stipulation requires the submission of an annual report detailing the
results of PHCC's subsidence monitoring inspections. This report contains descriptions of the local
terrain, geology, mining practices and details of the surface subsidence inspections.
Topography
PHCC operates the Roadside North and South Portals located 4 miles northeast of Palisade
Colorado. The surface terrain is typical for an arid mountainous region with moderately sloping hills
giving way to massive sandstone cliffs. Vegetation is limited to various grasses, sagebrush, saltbrush,
and a small population of pinyon junipers.
Geology
In the near vicinity of the mine property the rock strata are composed of three formations;
the Mt. Garfield Formation, the Hunter Canyon Formation and the Wasatch Formation.
The most important formation is the Mt. Garfield Formation because it contains three coal
seams of economic significance. These seams are the Palisade, the Cameo, and the Carbonera seams.
The Palisade Seam is 3 ft. to 4 ft. thick near the abandoned Midwest mine and rapidly thins
to the west, south and east. The Cameo Seam overlies the Palisade Seam by 400 ft. to 450 ft. and
is currently the only seam being mined in the immediate area. The Cameo Seam ranges in thickness
from less than 5 ft. to over 10 ft. and is the thickest in the north western parts of the property. The
Carbonera Seam overlies the Cameo Seam by 38 ft. to 93 ft. and is characteristically a series of
detached seams rather than a single seam. The remaining 200 ft. to 400 ft. of the Mt. Garfield
Formation consists of interbedded to laminated carbonaceous silty, fine to very fine grained
sandstones and carbonaceous sandy siltstones.
Overlying the Mt. Garfield Formation is the Hunter Canyon Formation. It consists of massive
brown - buff and gray sandstones and soft gray shale and ranges from 375 ft. in the west to 1,400 ft.
in the east.
Directly above the Hunter Canyon Formation is the Wasatch Formation. It ranges from 280
ft. to 790 ft. of variegated clay shales of fluviatile and lacustrine origin together with a few beds of
sandstone. The bulk of the formation is made of sandy and silty shales with sandstone constituting
less than 3 percent of the rocks in the formation.
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