2009-03-12_PERMIT FILE - M1999098

• Permit No: M1999098
• IBM Index Class Name: PERMIT FILE
• Doc Date: 3/12/2009
• Doc Name: Review of the Slope Stability Report
• From: DRMS-acs
• To: DRMS-ecs
• Email Name: ECS
• 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
Phone: [phone]
FAX: [phone]
March 12, 2009
Eric Scott
Allen Sorenson
Bill Ritter, Jr.
Governor
DATE:
TO:
FROM:
RE:
COLORADO
D I V I S I O N Of
RECLAMATION
MINING
SAFETY
Harris D. Sherman
Executive Director
Ronald W. Cattany
Division Director
Natural Resource Trustee
Review of the Slope Stability Report, Aggregate Industries, Riverview Resource Pit,
Amendment AM-O1, Permit No. M-1999-098
The Division of Reclamation, Mining, and Safety (DRMS) engineering staff has completed a review of the
slope stability report included with the above referenced permit amendment application. Based on the
stratigraphy illustrated in the geotechnical boring logs included with the stability report, the DRMS is
satisfied that the two pit wall cross sections analyzed in the report are the critical, conservative sections for
demonstration that nearby structures are outside the zone of potential damage if there were to be pit wall
slope failures. The DRMS further concurs that the shear strength values for the soil and bedrock layers
input to the stability model are conservative. The DRMS used Galena version 5.01 slope stability software
to conduct a verification analysis of the model included in the permit amendment application. The results
of the verification analysis are enclosed with this memorandum. Although the DRMS identified potential
failure surfaces with lower safety factors than those identified in the permit amendment stability report, the
safety factors are sufficiently high to assure that surrounding structures will be protected. Therefore, the
DRMS concurs with the conclusions in the slope stability report that surrounding structures will not be
damaged by land sliding of the excavated pit walls.
The amendment application states that there is a Suncor Energy gas pipeline located within 120 feet of the
proposed west mine limit. For pipelines of this type, the DRMS is concerned not only with the potential for
landslide failure to damage the structure, but also with the potential for the pipeline to be damaged by
flexure caused by slight earth movements caused by lateral stress relief through the excavation in the pit.
DRMS frequently requires that strain gauges be installed on pipelines adjacent to pits to monitor for
flexure. Other alternative monitoring measures may also be considered. However, it the understanding of
the DRMS that the Applicant will be providing a compensation agreement with the owner of the pipeline
that meets the requirements of section I I5(4)(e) of the Construction Materials Reclamation Act. If such an
agreement is supplied, monitoring of the pipeline will not be required by DRMS. Absent a compensation
agreement, the Applicant must provide the following information about the pipeline for a determination to
be made about the need for monitoring:
1. Pipeline material, diameter, and wall thickness.
2. Burial depth.
3. Pressure and flow rate.
enclosure(s)
c:\acs files\My Documents 4-19-06 thru\Riverview stability review.doc
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines