REV08778

• Permit No: C1981018
• IBM Index Class Name: Revision
• Doc Date: 5/7/1993
• Doc Name: DESARADO MINE C-81-018 TR 31 AND 32
• From: DMG
• To: JANET BINNS
• Type & Sequence: TR32
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room _' I5
Denver. CO 80203
Phone: [phone]
FAX:[phone]
DATE: May 07, 1993
TO: Janet Binns
FROM: Susan Morrison-~
RE: Deserado Mine (C-81-018)
Technical Revisions 31 and 32
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Roy Romer
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Michael B. long
Drvisian Director
This memo will follow up on my April 21, 1993 memo to you. On that dace, I spoke with
Gordon Bell of WFU about my concerns with recent submittals for the above mentioned
revisions. WFU has sufficiently addressed my previous concerns, the exception being
topographic drawings of the proposed sedimentation ponds. I am still unable to verify the
volume of the sedimentation ponds, and it would be extremely difficult for WFU to certify the
construction of the ponds with the current designs. Please inform WFU of the following
adequacy items:
1. The total depth of the secondary spillway for both the SDH#3 pond and the
SDH#4 pond is only one foot. Rule 4.05.6(11)(e) requires one foot of
freeboard above the water level when the spillway is flowing at design depth.
WFU should design the spillway to carry the 25 year - 24 hour storm event with
one foot of freeboard in the channel.
2. Rule 4.05.6(4) requires the crest of the secondary spillway be designed and
constructed one foot above the crest of the primary spillway. WFU has designed
the spillways so that the bottom of the secondary spillway is one foot above the
bottom of the principal spillway. Unless the flow depth in the secondary
spillway is greater than or equal to the depth in the principal spillway, the design
will not comply with Rule 4.05.6(4). WFU needs to revise the design to address
the difference in elevation between the crest of each spillway.
3. For both ponds, the secondary spillway is one foot above the elevation of the
sides of the embankment. WFU should redesign the embankment so that no
point of the embanlartent is the at or below the elevation of the secondary
spillway. Please refer to my crude sketch which I have attached.
SLM\050793B. WP