REP34815

• Permit No: C1981038
• IBM Index Class Name: Report
• Doc Date: 5/1/1991
• Doc Name: 1990 ANNUAL SUBSIDENCE REPORT
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

300 feet north of the 1st North, 2 1/2 West pane:L retreat
• mined from May thraxlh June, 1983. Station 6 lies adjacent to
the II West Submain development advanced in 1987. ;Station 6
pvhihited a 0.24 foot elevation loss following the retreat
minim of 1/2 West arcl has shown no discernable movement
since.
Stations 7-8: Surveys were initiated in August 1982 and continued biannually
through July 1984. Surveys were conducted once again in
November 1987. Stations 7 and 8 overlie approximately 750 and
1000 feet of Overburden respectively. 'These stations showed
no consistent subsidence effects evident thrtxx~ 1987.
Maximum subsidence noted at station 7 was measured at 0.06
feet from October 1983 to July 1984. No mining activities
were ongoing at that time in the vicinity of station 7.
Subsidence was noted in two years at station 8. Elevation
changes of -0.12 and -0.16 feet were noted in August 1983 and
November 1987 respectively. Mining development occurred in
the 1st North Mains adjacent to station 8 in January 1980.
Station 9-12: Surveys were initiated in August 1982 and oontirnied biannually
through July 1984. Stations 9, 10, aryl 11 were initially
surveyed after retreat mining had oaairred in the surrnundirx3
panels and shaved no significant movement thereafter. Station
12 subsided approximately 0.4 feet in the summer and fall of
1983 after retreat mining the underlying panel during the
spring. Station 12 Overlies approximately 550 feet of
• overburden.
Station 14: Station 14 is located in the Steven's Gulch alluvium
protective buffer zone over approximately 750 feet of
overburden. 'Ihe station was initially surveyed in June 1982.
Subsequent surveys were conducted annually since 1988. eta
indicates the station has seen an overall increase in
elevation totaling 1.13 feet. Panel G was advanced under this
station in September 1988. Retreat mining eocurred outside
the buffer zone adjacent to this site in February 1989. An
elevation adjustment of -0.55 feet was detected at this site
in October 1989 but was likely influenced by control station
coordinates being redefined. January 1991 data indicates 0.31
feet were subsequently gained. Overall subsidence effects
here appear to be minor.
Station 16: Station 16 overlies approximately 950 feet of overburden.
Surveys at station 16 were initiated in August 1982 and
continued biannually through July 1984. 'The 1st North, 3 West
panel adjacent to and east of station 16 was retreat mined in
October 1981. Panel A, located beneath station 16 is
scheduled to be pillared during the summer of 1991. Initial
movements due to the mining of 3 West appear negligible.
Station 17: Station 17 overlies the 1st North Main development at a depth
• of approximately 1100 feet. Mining under this point was
advanr~l in November 1980. Surveys were initiated in August
1982 and continued biannually throix~ July 1984. ~lertical
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