GENERAL42514

• Permit No: M1994117
• IBM Index Class Name: General Documents
• Doc Date: 3/18/1996
• Doc Name: WATER SPRAY EVAPORATION SYSTEM GOLD HILL MILL COM INC PN M-94-117
• From: DMG
• To: FOX ENGINEERING
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
DeUanmenl of Natural Resources
1313 Sherman SL, Room 215 Ila~
Denver, Colorado 80207 I
Phone: [phone]
FA%~ 13031 R72 P 106
DEPARTMENT OF
NATURAL
RESOURCES
March 18, 1996 ~ Roy ROmer
Governor
Mr. Richard FOX lames 5. LochheaA
6ecmive Direcmr
Fox Engineering Michael R. Long
1110 Oak Circle South Division oireaor
Broomfield, CO 80020-1065
RE: Water Spray Evaporation System, Gold Hill Mill, Coliaa Oro Molino,
Inc., Permit No. M-94-117
Dear Mr. Fox:
Thank you for the evaporation system design and estimates that were
provided to the Division via facsimile transmission this morning. Based
on your estimates, the proposed spray system in the Gold Hill Mill tailing
pond should be able to dispose of between 5 and 10.7 gpm of water by
evaporation. As you know, the Division has estimated groundwater inflows
to the Hazel-A adit averaged 1.7 gpm during the period from September 17,
1995 to January 21, 1996, and the Division and COM, Inc. have agreed that
these inflows have the potential to increase dramatically as a result of
snowmelt and spring runoff. In order to be prepared to evaporate as much
tailing pond and Hazel-A water as possible, and in an effort to maintain
a negative water balance that is critical for zero-discharge facilities,
COM. Inc. needs to install the tailing pond spray system detailed in your
design as soon as possible. The target date for completion of
installation and testing of the system, which has been discussed with COM,
Inc. representatives during previous meetings, is April 1, 1996. COM,
Inc. must provide the Division with a schedule for installation and
testing so that inspections can be conducted at appropriate times.
The Division will require that the spray heads be set-back from the pond
embankment such that the spray is wholly contained in the pond under
normally anticipated wind velocities. If any water from the spray system
begins to accumulate outside the lined area, the spray heads will have to
be repositioned or shut-off. Absolutely no runoff caused by operation of
the spray system is permitted.
The Division recommends that the spray system pump be located in a sump,
and that pond water entering the sump be gassed through a geotextile or
other type of filter.
Given the large degree of uncertainty in estimating evaporation rates, as
well as the degree of uncertainty in estimating seasonal variation of
inflows to the Hazel-A adit, the Division will require that contingency