REV101898

• Permit No: M1977342
• IBM Index Class Name: Revision
• Doc Date: 5/30/1996
• Doc Name: MINE FILL STUDY HENDERSON MINE PN M-77-342
• To: CLIMAX BOLYBDENUM CO
• Type & Sequence: TR4
• Media Type: D
• Archive: No

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May 30, 1996
Ms. Anne Beierle
Climax Molybdenum Company
P.O. Box 68
Empire, CO 80438
RE: Mine Fill Study, Henderson Mine, Permit No. M-77-342
Dear Ms. Beierle:
The Division has completed a review the proposed Henderson fill acid
drainage work plan, and has developed the following list of comments and
concerns:
1. The work plan proposal includes acid-base accounting, British
Columbia Research initial testing, and X-ray diffraction. The testing
protocol proposed will provide an adequate initial characterization for
acid generation potential, however, the Division is also concerned with
the metals generation potential of the Henderson Mine fill. This concern
is engendered by the definition of "Acid Mine Drainage" in the Hard
Rock/Metal Mining Rules and Regulations which st s that "Acid Mine 0
Drainage" means contamination of water by low pH or hea metals (emphasis ~
added). It is the Division's position that rep ' ntative samples of
Henderson Mine fill should be subjected to appropriate leaching tests to
characterize metals generation potential, in addition to the acid-base
accounting that is proposed. The selection criteria for appropriate
leaching tests would be based on the physical environment of the fill
materials. If the Henderson fill is subject to contact with meteoric
water that runs off the surface of the fill, or meteoric water that
infiltrates the fill but percolates quickly to an exit point from the
fill, then relatively simple meteoric water rinsing tests, with analysis
of the rinsate water quality, would be appropriate. The Nevada Meteoric
Water Mobility Test and EPA Method 1312 are examples of these types of
tests. If significant saturated zones are present in the fill, rinsing
tests would not provide complete characterization, and humidity cell,
shake flask, or other appropriate testing with concomitant mineralogical
analyses may be necessary. Jet~f«-- ~~.~tl. 2O
2. The work plan proposal suggests adoption of an ANP/AGP ratio of two
as the boundary between the zone of uncertainty and the potentially non-
acid generating field. The rational provided for adoption of this
relatively low boundary~is that X-ray diffraction data on mineralogical
composition of the fill materials will allow a more accurate description