REP12023

• Permit No: C1981034
• IBM Index Class Name: Report
• Doc Date: 9/9/1985
• Doc Name: RED CANYON MINE FIRST SEMI ANNUAL SUBSIDENCE REPORT PN C-81-034
• From: MLRD
• To: MIKE LONG
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

DEPARTMENT OF NATURAL RESOURCES III IIIIIIIIIIIII III
David H. Getcnes. Executnre Director
MINED LAND RECLAMATION DIVISION
DAVID C. SHELTON, Director
RiChartl D Lamm
Governor
DATE: September 9, 1985 ~ ~~
TU: Mike Long ._
~_- ..
FROM: Jim Pendleton _ ~-` ` ~~~~ ~-
RE: Red Canyon Mine - Fi tSemi-Annual Subsidence Report
(Permit ~ 4)
Pursuant to Tom Gillis's request, I have reviewed Grand Mesa Coal Company's
First Semi-Annual Subsidence Report, submitted to the Division August 1, 1985,
for the Red Canyon Mine. I forward the following comments for your
consideration.
(1) The report presents monitoring results for five of the eleven
potentially affected structures above the Red Canyon Mine Plan area. I
telephoned Larry M. Reschke, P.E., mine engineer for the Red Canyon Mine, to
inquire why only five of eleven structures had been surveyed. 'He responded
that only those five structures lie within the possible angle of draw above
the existing mine workings. This is an acceptable limitation to the
Division. I instructed him to clarify this point in future reports.
(2) Larry Reschke also observes that GMCC believes that no subsidence has
occurred above the Red Canyon Mine workings. Further, he states; "this
apparent movement is believed to be caused by surveying inaccuracies".
However, inaccuracies could also be due to movement from frost heave, etc.
Further, the observed subsidence may actually be occurring. For these
reasons, I believe it important to determine whether the monitoring program is
complying with required survey standards.
The U.S. Department of Commerce, National Oceanigraphic and Atmospheric
Administration (NOAA) published "Classification, Standards of Accuracy, In
General Specifications of Geodetic Control Surveys" in June of 1980. In this
document, NOAA states that subsidence studies should conform with the
standards for Second Order, Class II surveys (See attached xerox). These
standards are one part in twenty thousand for horizontal control and 1.3
millimeters times the square root of K (where K is the distance in kilometers
between points) for vertical control.
GMCC should describe in detail the applicable error limitations which Second
Order, Class II survey standards would impose upon their subsidence monitoring
survey program. They should determine whether their observed variance falls
within those limitations.
423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. [phone]