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REP33717
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REP33717
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Entry Properties
Last modified
8/25/2016 12:10:10 AM
Creation date
11/27/2007 6:37:05 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981014
IBM Index Class Name
Report
Doc Date
2/20/1987
Doc Name
SOUTHFIELD MINE SEMI ANNUAL SUBSIDENCE REPORT FOR PERIOD MAY - OCT 1986
Permit Index Doc Type
SUBSIDENCE REPORT
Media Type
D
Archive
No
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iii iiiiiiiiiiii iii <br />SOUTHF'IELD MINE FEE3 201987 <br />SEMI-ANNUAL SUBSIDENCE REPORT _ <br />FOR PERIOD MAY - OCTOBER, 198.6 _ MINED tAND <br />f~ECLAMATION DIVISION <br />(STIPULATION NO. 11 OF PERMIT C-81-014) <br />Introduction <br />This report has been prepared to summarize subsidence monitoring <br />results and to state subsidence predictions based upon the present <br />subsidence monitoring program. Survey monitoring for the purpose <br />of this report was performed on the South Grid, City of Florence <br />Water Line, Thompson Ranch Structures, and the Newlin Creek <br />Streambed as required. <br />Survey data I~as been presented on four summary tables, each of <br />which compares results of the most recent survey to the pro- <br />ceeding survey and to the original survey to indicate the magni- <br />tude and direction of movement for each monument and structure. <br />The survey data for both monument lines of the South Grid is <br />portrayed in cross sectional form to depict the total subsidence <br />as of the most recent survey. <br />The report is presented in sections, for each of the items moni- <br />tored, with observations and predictions. <br />South Subsidence Grid <br />Survey data for the South Grid monuments indicates similar trends <br />as compared to the previous six month survey period. The maximum <br />subsidence detected to date is 1.88 feet at Monument 15, a change <br />of 0.16 from the preceeding survey. The subsidence is much less <br />than the predicted 5.0 feet based on the retreat mining of the 2 <br />South "B" and "C" Panels. Maximum subsidence as a result of <br />retreat mining "A" Panel is a total of 1.14 feet at Monument 4. <br />The magnitude of movement- is comparable to the maximum predicted <br />subsidence of 1.46 feet by Rocky Mountain Geotechnical (RMG) in <br />the Mining Permit. <br />Tile rate of subsidence continues to be greatest along the north <br />arm of the grid from Monument 11 to Monument 15. Survey data <br />indicate changes ranging from 0.14 to 0.16 feet for the current <br />period. Data from the previous six month report indicate movement <br />of the same monuments ranging from 0.19 to 1.43 feet. The measur- <br />ed decrease in the rate of subsidence is probably due to the <br />consolidation of the underground caved area. It is anticipated <br />that the rate of movement will continue to decrease resulting in <br />minimal additional subsidence. <br />Survey data from the south arm of the grid as portrayed on the <br />cross section indicates an apparent angle of draw of between 19 <br />and 29 degrees. This is generally consistent with the range of 20 <br />to 25 degrees predicted by RMG in the Mining Permit. Continued <br />survey monitoring should improve the reliability of predicting the <br />
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