2006-02-21_REVISION - M1983141

• Permit No: M1983141
• IBM Index Class Name: Revision
• Doc Date: 2/21/2006
• Doc Name: Cost Estimate for Water Impounding Bulkheads
• From: DMG-acs
• To: DMG-tas
• Type & Sequence: AM2
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE: Februazy 21, 2006
TO: Tom Schreiner ~i/
FROM: Allen Sorenson ~~/
COLORADO
DIVISION O F
MIN SRALS
GEOLOGY
0.ECLANATrON•N INING
SAfETY•ECIENCE
Bill Owens
Govenwr
Russell George
Executive Director
Ronald W. Cottony
Division Director
Natursl Resource Trustee
RE: Cost Estimate for Water Impounding Concrete Bulkheads, Mount Royale Ventures LLC,
Cash and Who Do Mines, PermitAmendmentAM-02, Permit No. M-1983-141
The Division of Minerals and Geology (DMG) engineering staff have completed a review of the
underground water impounding bulkhead information provided in the Cash and Who Do Mines permit
amendment AM-02 application. The Applicant proposes a main bulkhead 330 feet inby of the Mount
Royale No. 1 Adit portal where the edit dimensions are 8' x 8' and there is approximately 149 feet of
Bound cover. A secondary bulkhead is proposed for a location 140 feet inby the portal with the same edit
dimensions and where there is approximately 65 feet of ground cover. The AM-02 application provides no
design or design basis information for the bulkheads, and since the DMG must secure reclamation bond for
construction of the bulkheads, this memo provides an analysis of the type of bulkheads that will be
necessary in order to develop costing information and estimate the amount of bulkhead bond to be required.
Einarson and Abel (1990) present astep-by-step procedure for design of underground water impounding
bulkheads. Conservatism in design of the bulkheads is necessary because of the safety and environmental
implications of a bulkhead failure, the long life required for the bulkheads, and the ultimate inaccessibility
of the bulkheads. The American Concrete Institute's "Building Code Requirements for Reinforced
Concrete (ACI 318-89)" is used because the bulkheads are analogous to reinforced deep-beam concrete
structures and because of the inherent conservatism of the code. The analysis presented in this memo
generally follows the Einazson and Abel template.
The Mount Royale Adit No. 1 portal is at elevation 7830 feet. The edit was driven as an incline for the first
330 feet rising at one and one half percent; the edit then declines at one percent to the intersection with the
third level Cash Mine workings. The Applicant proposes to install the main bulkhead at or neaz the grade-
break in the edit, and to install a second bulkhead 140 feet inby the portal. Hence, the elevation of the
proposed bulkheads are calculated as follows:
330'x 1.5% = 4.95' 7830'+4.95`= 7834.95'
140'x 1.5% = 2.1' 7830'+2.1'= 7832'
Elevation of the main bulkhead is 7835 feet; elevation of the second bulkhead is 7832 feet. The top of the
ridge northwest of the proposed bulkhead locations is at elevation 8447 feet. The ridge elevation represents
the maximum potential hydraulic head that may develop at the main bulkhead. DMG recognizes that in
order for this amount of head to develop, other mine openings would have to be plugged. If head were to
develop behind the proposed main bulkhead resulting in discharge at, for example, the collapsed Cash Mine
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey