PERMFILE62559

• Permit No: M1999098
• IBM Index Class Name: Permit File
• Doc Date: 1/20/2000
• Doc Name: TECHNICAL ADEQUACY REVIEW OF SLOP STABILITY ANALYSIS FOR NEW 112 RECLAMATION PERMIT APPLICATION PN M
• From: DMG
• To: CAMAS CO INC
• Media Type: D
• Archive: No

III IIIIIIIIIIIII III
STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 51., Room 215
Denver, Colorado 80203
Phone: [phone]
FTX: [phone]
January 20, 2000
DIVISION OF
MINERALS
GEOLOGY
RECTA MATION
MINING•SAFETY
Mr
Mike Refer Bill Owens
.
CAMA$ Co. II1C. Governor
Greg E. Watcher
7108-M South Alton Way Execmive Director
Englewood. CO 80112 Michael B. Long
Dro~sion Dveaor
RE: Technical Adequacy Review of Slope Stability Analysis for New 112 Reclamation Permit
Application, Permit No. #M-99-098, Riverview Resources
Deaz Mr. Refer,
This letter is being written address technical issues in the Slope Stability Analysis submitted
January l2, 2000, for the new 112 application submitted by your company, Permit No. #M-99-
098, Riverview Resources Pit. These issues must be resolved before the Division of Minerals
and Geology (DMG) can approve this application; However, this is only.a preliminary review of
this slope stability analysis, pending the submittal,of a full analysis of the hydrological concerns
detailed in the Technical Adequacy Review dated December.l6, 199..9; Specifically; items 3, 5,
and 6.of the main, DMG review, and.items .1, 2b, 7,.8 and 9 in Tom,Schreiner'sreuiew. must be.
addressed before any final determination regarding slope stability at the site can be made. Please
address the following concerns prior to the due date of February 4, 2000.
1) The presence of de-watering trenches was not included in any of the case analyses. Since the
presence of water at the toe of the excavated slopes could effect the phreatic surface within
the mined azeas, this must be included in all cases.
2) The 0.5-foot to 3-foot thick weathered claystonelayer directly above the claystone bedrock
was omitted from ali analyses, and must be included. 'The soil boring logs indicate [hat the
average thickness of this layer on the west side of the site is 0.7 feet, and that an average of
1.6 fee[ is present on the east side of the site. Analyses should be done for the maximum
thicknesses as well as the average values of these layers, assuming zero cohesion and
detailing the appropriate effective friction angles and strength values.
3). The reference source used to determine the assumed strength values, angles of internal
friction, and cohesion values for the soils used in this analysis is not clear, because the soils ,
_" aze no['classified under standard..ASTM labels.-Please submit the name of the reference.work
"frorri which these,.values.were obtained, or submit,site-specific valuesfrom standazd~soil
`'strength tests.lione.at the site. A lithographicprofile of the soils, including wet and,dry ~: r ;
density, soil composition, internal friction angles, cohesion, and phreatic surface,.is . ,- r
recommended.