1992-02-10_GENERAL DOCUMENTS - C1981017 ‎(2)‎

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 2/10/1992
• Doc Name: Bid Documents ‎(IMP)‎
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

Memo to Candace Thompson
Re: Coal Basin Mines - Subsidence
page 3
Dr. Collins requests, in his October 25, 1988 letter report, that "resumption
of the monitoring program be limited to annual visual inspection and
reporting". He observes that no structures or renewable resource lands are in
jeopardy from the ridge-line landslide. Because all of the potentially
affected area lies within the existing Permit boundary and no structures or
renewable resource lands are in jeopardy, the Division believes that a
subsidence monitoring program limited to annual visual inspection of the
potentially affected area and submission of a report is adequate. However,
prior to the conduct of double-pass longwall extraction or consideration of
any future requests for amendment of the mine plan which involved expansion of
the potentially subsided area, the Division will require the operator to
revise the subsidence report submitted in December, 1985 to reflect the 1988
subsidence resurvey data.
Compliance with Stipulation (2 )
In accordance with revision stipulation (2 ), the monuments have been
maintained, as evidenced by their use in the completion of the Fall of 1988
subsidence resurvey.
Compliance with Stipulation (3)
The permit in effect at the issuance of that revision approval expires in
1988. In accordance with revision stipulation (3), MCR performed a resurvey
of the twenty subsidence monuments in September of 1988. MCR submitted a
letter report, dated Sept mber 26, 1988, tabulating the survey data gathered
during the 1988 subsidenc monument survey. The data demonstrates that many
of the monuments experien ed significant residual vertical subsidence
following the 1985 subsid nce monument survey. For purposes of comparison the
Division briefly revised he determination of subsidence factor contained in
Dr. Collins' 1985 report o reflect the Fall of 1988 total vertical subsidence
data. The following is a partial revision of Table 2 from that report.
CALCULATED SUBSIDENCE RATIOS
(Revision of Table 2 - December 1985 Report by Dr. Collins )
Point Total Total Coal Subsidence
Number Subsidence Removed Ratio
TP-1 -2.41 9.00' 0.27
TP-2 - 0 -
TP-3 - 0 -
TP-4 -0.81 ' 8.00' 0.10
TP-5 -1 .74' 15.00' 0.12
TP-6 -3.50' 10.00' 0.36