1998-08-17_REPORT - C1981038 ‎(5)‎

• Permit No: C1981038
• IBM Index Class Name: Report
• Doc Date: 8/17/1998
• Doc Name: ANNUAL SUBSIDENCE REPORT
• Annual Report Year: 1989
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

• SUBSIDENCE IMPACTS 1989
Cyprus Orchard Valley completed pillar extraction of Panel and
advance development of Panel H through crosscut 32.
The following are discussions of monitoring and impacts divided
into survey and visual observations respectively. Subsidence
monitoring data is contained in Appendix G.
Survey Monitoring
The COVCC Survey Monitoring Program within the present permit area
consists of a wide-spaced grid of survey monuments and three high-
resolution grids. The main emphasis has been placed on wide-spaced
grid stations with the drainage buffer zone areas of East Roatcap
and Steven' s Gulch and also the close-spaced grids overlying 9th
East, 5 North 1 West, and the 11-12 North area of undermining.
The monitoring stations were surveyed once during 1989 as approved
by MLRD for reduction of subsidence monitoring frequency. Field
surveying employed a double angle/double distance method to
increase accuracy, Data reduction was then completed by the
surveyor and entered on cumulative data sheets.
The 1988 Subsidence report made reference to the possibility of
• control station movement and the need for checking the actual
locations of these control points. This check was done in 1989 and
is scheduled for re-verification in 1990. This check verified
movement has occurred at the control points and for the most part
are the basis for the change in elevation of the subsidence points.
Otherwise, survey data indicated that subsidence has virtually
ceased within the close-spaced grid points 28-69 except for a
couple of stations.
High-resolution grid stations 201-224 showed downward movement of
between . 40 '-.80' indicating minor subsidence in this area. Again,
this movement can be directly correlated to the checks made on the
control station locations.
The 1988 report referred to observed movement occurring adjacent to
the 9th East panel. These changes are probably the result of
movement in control station I. Locations of the control stations
will be reviewed and possibly moved in conjunction with the 1990
subsidence survey for a more accurate control of information in the
future.
As expected, little if any subsidence occurred over the Orchard
Valley West Mine area during 1989. Survey results of stations 6,
14 , 89, 90, 92 and 93 verify this conclusion.
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