REP47615

• Permit No: C1981035
• IBM Index Class Name: Report
• Doc Date: 10/25/1989
• Doc Name: NATIONAL KING COAL MINES SUBSIDENCE MONITORING REPORTS
• From: MLRD
• To: DAN MATHEWS
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

• iii iiiiiiiiuiiiiii •
999
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Roy Romer, Gove
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Dlreetor
DATE: October 25, 1989
T0: Dan Mathews )
FROM: Jim Pendleton ~ - /
RE: Nationa ing C Mine's Subsidence Monitoring Reports
In response to your request, I have reviewed the past National King Coal mine
subsidence reports. I have also referenced my old notes regarding the permit
approval conditions concerning subsidence monitoring. The permit application
addressed ground subsidence in section 2.05.6. The subsidence inventory of
the permit area found no renewable resource areas and only one structure, the
poorly maintained and sporadically used Huntington irrigation ditch, within
the potentially affected area. No bedrock or surficial groundwater aquifers
were determined to exist within the potentially affected area. The
application projected; "Severe tension cracks or joints of widths greater than
fractions of an inch or lengths greater than five to ten feet are not
expected." The Division questioned the applicant's projection of limited
subsidence cracking but concurred with the applicant's inventory and approved
the proposed quarterly visual inspection subsidence monitoring plan.
The operator's third and fourth quarter of 1989 subsidence monitoring reports
have documented the occurrence of tension cracking above the 3rd East panel at
the National King Coal mine. As of October 6, 1989, three subparallel
fractures, striking near E-W, were detected in the central portion of the
S 1/2 of the N 1/2 of the SW 1/4 of Section 32, T35N, R11W. "The northernmost
fracture is approximately 311' in length, discontinuous and varies in width
from a hairline fracture to 0.2'. The central fracture lies approximately 30'
south, is approximately 270' in length, discontinuous and also varies in width
from a hairline fracture to 0.2'. The southernmost fracture lies
approximately 15' farther south, is approximately 80' in length, is continuous
and varies in width from a hairline fracture to slightly less than 0.1 '. No
downward movement of the surface is apparent." Further, the subsidence report
states; "It was mutually agreed (by the geotechnical consultant and the
surveyor) to establish two survey points over 3 East with a control point over
unmined ground between 2 East and 3 East for survey monitoring. These points
will be closely monitored on a weekly basis, both visually and by instrument
until the ground becomes covered by snow."
The occurrence of subsidence tension cracking has obviously demonstrated that
the applicant's original projection of the limited nature of ground cracking
was in error. However, the results of the subsidence inventory are still
valid. The only item potentially in danger of material damage remains to be
the Huntington Ditch. The observed subsidence cracking could conceivably
215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]