GENERAL36310

• Permit No: M1980244
• IBM Index Class Name: General Documents
• Doc Date: 12/29/1994
• Doc Name: CAPPING OF CRESSON MINE WORKING AREA
• From: DMG
• To: MINERALS STAFF
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Deparlmenl of Natural Resources
131 3 Sherman St.. Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: U03) 832-8106
DATE: January 3, 1995
TO: Berhan Keffelew
FROM: Allen Sorenson ~~
L '~
~~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
lames 5. Lochhead
Executive Director
Michael B. Long
RE: Capping of the Cresson Mine Workinq Area, Cripple LaY"~~~'feCd4`
Victor Gold Co., Cresson Project, Permit No. M-80-244
I have reviewed the cross-section of the proposed cap presented in your
12/29/94 memo. In order to assure that the cap will be effective in
minimizing infiltration, I would recommend that a rigorous set of
enforceable specifications be prepared. Particle size gradation for the
12 inches of compacted overburden should be specified; this material
should be well graded with a minimum required percentage of fines, and
a maximum percentage of large particles specified. The moisture content
range at which the material will be compacted should be specified.
Also, the frequency of maximum achievable density and optimal moisture
content determinations (i.e. Proctor tests) should be specified, and the
testing procedures to be utilized described (Modified or Standard
Proctor, ASTM designation). The type and frequency of moisture/density
determinations for the compacted overburden should also be an
enforceable permit parameter.
The 3-foot section of overburden included in the cap design should also
be subject to enforceable specifications. This material should not
exceed a specified maximum percentage of fines, and would preferably be
a relatively coarse grained material. Best management practices should
be incorporated into the specifications to assure that the 3-foot layer
of overburden is not subject to excessive equipment traffic once it is
placed, as this could lead to over-compaction.
Both the compacted 12 inch section and the loose 3 foot section of the
proposed cap should be subject to permeability testing, either in situ,
or on representative samples in the lab.
The specifications can be approved to allow a certain degree of
flexibility in material selection and placement. We are not requiring
the type of cap that would be placed at a RCRA site for example.
However, if we do not have an enforceable set of material specifications
for the proposed cap, beyond the section depicted in your 12/29/94 memo,
the result could be an ineffective, or leaky cap.
C:~WPSI~CRESSON.41