REP36181

• Permit No: C1981038
• IBM Index Class Name: Report
• Doc Date: 11/23/1988
• Doc Name: ORCHARD VALLEY MINES 1988 SEMI ANNUAL SUBSIDENCE REPORT PN C-83-038
• From: MLRD
• To: JEFF CLAPTON
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

• • iiiiiiiiiiiniiiiii
999
STATE OF COLORADO
Roy Romer, Governor
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Director
DATE: November 23, 1988
T0: Jeff Clayton 3
FROM: Jim Pendleton / ~^
RE: Orchard ley Min 1988 Semi-Annual Subsidence Report"
(Permit # C-83-038)
I have reviewed the semi-annual subsidence report submitted on November 10th
by Colorado Westmoreland, Inc. for its Orchard Valley Mine. This report
presents a tabulation of the survey data generated by the survey of the
close-spaced and wide-spaced monitoring monuments installed above the
underground workings at the mine. The mine has undergone minor residual
subsidence since the closure due to an underground fire. In general, past
subsidence data has shown relatively conventional ground response with normal
data scatter for monuments above one panel or another.
The most recent survey, performed in August of this year, purports to document
a somewhat different character of subsidence. The close-spaced monuments and
a few associated wide-spaced monuments show relatively uniform rises in
elevation. The company interprets this to document uniform cantilevered rise
in the ground surface in these areas of the permit area. This is possible and
has been documented at other mines in Colorado. However, the strangely
consistent amount of rise in each set of monuments, combined with what would
be a departure from past subsidence character at the mine, leads me to suspect
that the movements are largely "apparent", rather than actual.
An examination of the affected monuments determines the following information:
Monitoring Vertical Control
Station No. Movement Station No.
42 +0.29' 43
43 +0.32'
44 +0.34'
45 +0.32'
46 +0.32'
47 +0.31' 46
48 +0.32'
49 +0.31'
50 +0.25'
5] +0.30'
215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]