PERMFILE105210

• Permit No: M2006003
• IBM Index Class Name: Permit File
• Doc Date: 3/13/2006
• Doc Name: Adequacy Review
• From: DMG esc
• To: Hall-Irwin Corporation
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINFRALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE:
T~:
FROM:
RE:
Mazch 13, 2006
Erica Crosby
Richazd M. Wenzel III, P.E., P.G. t//^l
COLORADO
DIVISION O F
MINERALS
GEOLOGY
0.FClA NATION•NINING
EAf ETY•SCIFNCE
Bill Owens
Governor
RusseN George
Executive Director
Ronald W. Uttany
Division Director
Natural Resource Trustee
Mining Setbacks from Permanent Valuable Structures, Hall-Irwin Corporation,
Parker/Dersham Sand and Gravel Resource, DMG Permit No. M-2006-003
The Division of Minerals and Geology (DMG) engineering staff have completed a review of the stability
analyses and proposed mining setbacks prepared by Civil Resources, LLC as part of the Parker/Dersham
Sand and Grave] permit application. The purpose of this letter is to address the adequacy of the slope
stability analyses in accordance with Rule 6.4.19, Exhibit S -Permanent Man-Made Structures, of the
Mineral Rules and Regulations of the Colorado Mined Land Reclamation Boazd for the Extraction of
Construction Materials.
Documents reviewed for this permit application included a summary letter; geotechnical boring logs
prepazed by Tetra Tech RMC; slope stability analysis outputs; the Pre-Mining Plan Map, Fig. 1; the Mining
Plan Map, Fig. 2; and the reclamation Plan Map, Fig 3.
The slope stability analyses for this site included eight cross-sections {A-A' thru H-H') at various locations
across the site. The Factors of Safety (FOE), as listed in the summary letter, vaned from 1.009 to 2.29.
Based on the geotechnical data used to analyze the proposed slopes, the proposed slopes appeaz to have an
adequate FOS to prevent damage to the adjacent man-made structures. However, several discrepancies in
the analyses were observed and need to be addressed or clarified. Those discrepancies are as follows:
Locations of cross-sections do not appear on any of the figures. Identifying locations of cross-
sections on at least one fgure will eliminate any guesswork as to where the cross-sections were
analyzed. Since the text on page 3 of the summary letter indicates that the cross-section
locations aze identified on Fig. 1, please change Fig. I so that the cross-sections aze shown on it.
2. The Mining Plan Map, Fig 2, indicates that overburden and topsoil stockpiles will generally be
located along the exterior perimeter of the proposed mining limits. However, surchazge loads
due to overburden and topsoil stockpiles were not included in any of the analyses. Because
several of the slopes analyzed had factors of safety slightly greater than I, it is possible that
surchazge loads from topsoil or overburden may reduce several of the factors of safety to less
than 1. Please include surchazge loads from the topsoiUoverburden stockpiles in the calculations
where appropriate.
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey