REV91728

• Permit No: C1996083
• IBM Index Class Name: Revision
• Doc Date: 5/18/2006
• Doc Name: Adequacy Review & Attachments
• From: DMG
• To: Bowie Resources, LLC
• Type & Sequence: PR10
• Media Type: D
• Archive: No

DIVISION OF WATER RESOURCES
WATER DIVISION FOUR
Office of the State Engineer
Department of Natural Resources
1871 E. Main Street
P.O. Box 456
Montrose, Colorado 81402
Phone [phone]
Fax [phone]
http://water.state.co.us/
Joseph Dudash
Co. Div. of Minerals & Geology
1313 Sherman St., Room 215
Denver CO 80203
June 12, 2003
Re: Bruce Park
W. Div. 4, DAMID: 400125
Subject: Bowie No. 2 Mine -Bruce Park Dam Study
Dear Mr. Dudash:
Hal D. Simpson, P.E.
Stale Engineer
Prank 1. Kugel
Acting Division Engineer
I have completed review of the subject study trarismitted under cover letter from Mx. Jim Stover
dated October I5, 2002. The purpose of this letter is to provide you my comments pertaining to the study
results relative to potential impacts to the Bruce Pazk dam resulting from mining activity associated with
expansion of the Bowie No. 2 Coal Mine.
Mx. Stovex's letter stated mining would progress to within as close as 1300 feet of the dam site based
on the revised mine plan. Furthermore, Mr. Stover asserted the slope distance would be 2,470 feet based
on the assumed depth of 2,100 feet fox mining activity. Regardless of the implications of the study results,
the relevant stipulations of TR-22 for monitoring were based on horizontal distances from the dam site to
the active long-wall mining operation.
The subsurface investigations and evaluations of the dam's performance under the anticipated level
ofseisrtJicloadingrevealednopotendalweaknessesintheembankmentorfoundation. Based on the results,
the report concludes the embankment dams "should notbe adversely impacted" by mine induced seismicity.
The report does not make any conclusion regarding potential for ground subsidence in proximity of the
dams. Based on the analyses provided in support of the conclusion, the risk of the dams failing due to the
seismic loading analyzed appears minimal. Results pertaining to analysis of the landslide located upstream
of the right abutment of the main dam, however, warrants further discussion.
Subsurface investigations of the landslide identified a possible "slide zone" at a depth of 19.5 feet
in boring BL-102 (maximum depth 35~ located in the lower 1/3 of the slide. A notation for a possible slide
zone was also on the log for boring BL-lOlA (maximum depth 30~, middle of the landslide, at a depth of
14.5 feet based on "no recovery." No shear testing was performed on samples to determine strength of
material comprising the slide zone. Instead, the shear strength of the potential slide zone was determined
from a static stability analysis model, varying the strength of the material comprising the assumed failure
zone until a factor of safety of 1.0 was achieved. The model of the landslide depicted pre-failure conditions
and a presumed geometry for the original hillside. In addition, the stability model assumed a maximum level
for the phreadc water surface, which in turn yields a maximum shear strength for a given factor of safety,
in this case FS=1.0. Three-dimensional effects were not considered in the back-analysis. Because of the
STATE OF COLORADO
pF' p0~
RECEIVED .+~_
~~ `r{~p JUN 16 2003
~ ~~ ~+N Givision of Minerals and Gealagy Bill Owens
'~pp Govemar
Or Greg E, Watcher
Executive Director