2009-10-05_REVISION - M1987049 ‎(17)‎

• Permit No: M1987049
• IBM Index Class Name: REVISION
• Doc Date: 10/5/2009
• Doc Name: Adequacy Review #6, Stability Exhibit
• From: DRMS
• To: Hart Environmental
• Type & Sequence: AM2
• Email Name: JLE
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203 C O L O R A D O
Phone: [phone] D IVI S ION OF
RECLAMATION
FAX: [phone] M I N I N G

SAFETY
Bill Ritter, Jr.

DATE: October 2, 2009 J Governor
o
Harris
Sherman
Executive Director
FROM: Allen Sorenson Ronald W. Cattany
Division Director

TO: Jared Ebert Natural Resource Trustee
RE: Review of Proposed MiningSetback& Ready Mixed Concrete Co.,
Bromley Fakes Pit, Amendment AM?J2, Permit No. M-1987-049 ?
The Division of Reclamation, Mining, and Safety (DRMS) engineering staff has reviewed the revised mine
plan and geotechnical stability exhibit for the above referenced application, including the stratigraphic
information provided in cross sections developed from the test holes that have been drilled on the property,
and has identified the following issues.
The DRMS has completed confirmation analyses for slope stability for excavated pit slopes adjacent to
McCann Ditch, along Brighton Road, and adjacent to the Spier Property. The DRMS analyses confirm
that the setbacks proposed for Brighton Road and the Spier Property are adequate to prevent damage from
slope failure. However, the DRMS analysis of the proposed setback from McCann Ditch found an
unacceptably low safety factor of less than one. The Applicant should review the DRMS analytical
results enclosed with this memo, and must propose a setback from McCann Ditch with a safety factor
greater than one.
2. The stability analyses included in the application are for relatively large-scale earth movements, such as
deep-seated circular or non-circular slip surfaces. The DRMS is concerned that smaller scale strains, such
as may be caused by relief of pre-existing stresses in the bank when the gravel is excavated, may be
sufficient to adversely affect the Xcel Energy gas pipeline that runs adjacent to a proposed mining area
along Brighton Road. For this reason the installation of strain gauge emplacements on the pipeline would
be a reasonable and prudent measure to detect any small movements in the pipelines that may occur.
Early detection of small movements in the pipelines would allow for timely stress relieving measures that
would prevent damage. In summary, the DRMS position on the installation of strain gauges is that:
a. Pipeline are critical structures, and the consequences of pipeline failure could be catastrophic. As
such, a high degree of conservatism is called for in determining appropriate measures to protect the
pipelines.
b. Strain gauges are an accepted and easy-to-use pipeline-monitoring device that can be installed at a
reasonable cost. The added degree of pipeline protection provided by strain gauges can be realized
relatively inexpensively; requiring their installation is a prudent addition to the proposed mine plan.
c. The DRMS has conferred with leading experts in the pipeline industry, including pipeline consultants,
pipeline operators, pipeline installers, and the Colorado Public Utilities Commission, and has found
that there is precedent and consensus on the need for pipeline strain monitoring during major
excavation operations in the vicinity of critical pipelines.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines