REV03009

• Permit No: C1996083
• IBM Index Class Name: Revision
• Doc Date: 3/6/2003
• Doc Name: Geotechnical Completeness Review Memo
• From: Byron Walker
• To: Joe Dudash
• Type & Sequence: PR7
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 6L, Room 215
Denver, Colorado 80203 D l V 1 5[ O N O F
Phone: [phone] 1V1 I N E RA L $
FAX: (303) 832A706 &
GEOLOGY

Interoffice MEMORAlvDiT1VI RECLAMATION
MINING•SAFETY

Bill Owens
to: Joe Dudash . / Governor
from: Byron G. W „Ke~r/~/ Greg E. watcher

subject: Executive Director
Geotechnical Completeness Review, PR-7, B-Seam Portals, PR-8, B-Seam Mlll>}IP31d W
Cattan

Plan, Bowie No. 2 Mine, Pem3it No. C-96-083, Bowie Resources LTD .
y
Division Director
date: Mazch 6, 2003
This memorandum is in response to your request for assistance, memo dated Mazch 3, 2003,
same subject. Thank you for your assistance in locating subject material in the approved Permit.
In summary, I believe the geotechnical information provided to date is not adequate to evaluate a
couple of items. However, this might be considered an adequacy item and the application might
be found complete. In addition, there aze a number of technical adequacy issues identified in this
preliminary review. -
I have reviewed the work accomplished by, and concerns of, Jim Pendleton. These concems
appeazed to have addressed in the currently approved Pem3it, but the concems still apply to new
work.
PR-7, Item 1. Is the fifty-foot high cut slope in the vicinity of 33,000E 19,400 N (Map No. 15-2,
Sheet 2 of 4) in solid rock or surficial materials? The Rules pernut slopes as steep as 1 horizontal
to 4 vertical (lh:4v) in rock for haul road cuts. The cut bank at this portal bench is lh:2v, more
similaz to a portal face-up. Maybe we have some approval to go by for the portal face-up. The
Geotechnical Engineering Report Slope Stability Analyses Bowie Min4e No. 2 Delta County,
Colorado Terracon Project no. 65995058 (Tab 9 of Volume VII - Geotechnical Studies) indicates
a critical cut slope at the transfer bench. A factor of safety of 1.38 was concluded for a Case I,
where the cut slope was lh: 0.67v. Information at Tab 1 of Exhibit 9 indicates that cut slopes at
the site should not be steeper than 1h:0.5v unless in very stiff to hazd clays where 1h:0.67v
should be acceptable where risk of slope failure could be accommodated. Recommend the
geotechnical investigation demonstrate that the cut is in rock, and consider both dip and strike of
formations (bedding planes) and any moisture in the azea; or present a demonstration of stability
of the cut slope at lh:2v in the site specific surficial soils at the cut. A request to the applicant
might be: Please expand the geotechnical investigation to demonstrate that the proposed
portal bench lh:2v cut is in rock, and consider both dip and strike of formations (bedding
planes) and any moisture in the area; or, if in surficial soils, present a demonstration of
stability of the cut slope at lh:2v in the site specific surficial soils at the cut.
PR-76, Item 2. The post-mining reclamation topography (Map No. 18) calls for filling in the
portal bench, but no information was found to support stability of drainage across the reclaimed