2018-08-22_REVISION - M1977493A

• Permit No: M1977493A
• IBM Index Class Name: REVISION
• Doc Date: 8/22/2018
• Doc Name: Request for Technical Revision
• From: Climax Molybdenum
• To: DRMS
• Type & Sequence: TR28
• Email Name: ECS
• Email Name: MAC
• Media Type: D
• Archive: Yes

Technical Revision (TR-28) Climax Molybdenum Company
Environmental Protection Plan Permit No. M-1977-493
flocculent used in the water treatment process will remain at the site until no longer required in the water
treatment process. Removal and disposal of water treatment chemicals will occur as discussed for mill
process chemicals during periods of temporary cessation or prolonged lack of mineral production.
T-4 Acid-Forming Materials and Acid Mine Drainage
The Climax ore body beneath Bartlett Mountain contains unoxidized sulfides that, in the presence of
oxygen, water, and bacteria, have the potential to become an acid-forming material as defined in Rule 1,
Section 1.1(1). Likewise, waste rock materials deposited in McNulty OSF, North 40 OSF, and tailing
material deposited in the TSFs also contain material with acid-forming potential. Climax concurred with
this fact in its response to the DRMS (August 31, 1994) when it accepted the DRMS determination that
Climax was a DMO under the amended rules. In addition, water that percolates through the open pit area
and accumulates in the pit or closed underground workings contacts sulfide bearing material and, in turn,
has the potential to become acidified, thus, meeting the definition of "Acid Mine Drainage" in Rule 1,
Section 1.1(2).
Overburden material will be handled during operations, to the extent practicable, to minimize the
generation and impact of acid drainage as well as the volume of water requiring treatment during and
after mining. As overburden material is placed as part of ongoing operations, Climax will continually look
for and identify opportunities to manage overburden materials to minimize acid rock drainage and the
volume of water requiring treatment. Techniques will include, but may not be limited to, material
segregation (based on acid generating potential), upgradient diversion of unimpacted water, and Climax's
election to implement concurrent reclamation to minimize future acid drainage and the quantity of water
requiring treatment. Concurrent reclamation of OSFs is described in Exhibit E of AM-06. As required
under Rule 6.4.21(6), appropriate EPFs have been identified to minimize, capture and treat acid mine
drainage (see Section T-5.3).
The locations of OSFs have been developed with consideration of existing conditions as well as overall
technical and economic feasibility. As described in Exhibit D of AM-06, overburden placement will consist
of additional placement in the area of existing E and F dumps as well as the existing McNulty OSF. TR-
25 includes OSF design, stability analyses, and an operations and monitoring plan. TR-25 also includes
final designs for seepage collection and run-on and run-off control facilities to minimize the impact of
potential acid drainage associated with these facilities.
The acid-forming materials will remain in-situ at Climax following final termination of mining and
processing activities. As discussed herein, as long as acidic drainage with the potential to affect the
environment is released from these sources, such drainage will be managed according to the stipulations
and requirements of the appropriate regulatory permits in place at the time.
The geochemical processes at the site are well understood to ensure the effectiveness of the water
management and treatment system. Table T-E-6, included in Appendix T-E (Geochemical Data) is from
EPP R3 (TR-24) and presents a summary of water quality data from impacted sources, including seepage
from the OSFs, TSFs and other sources from around the site that are collected and treated. Samples of
impacted water sources will continue to be collected by Climax on an as needed basis.
T-4.1 Temporary Cessation/Prolonged Lack of Mineral Production
Surface water discharge at Climax is regulated under the CDPS Permit as discussed in Section T-2.2.
Under temporary cessation or a prolonged lack of mineral production scenario, mine waters, storm water,
and seepage waters would continue to be managed, treated and discharged according to the conditions
of this permit.
T-4.2 Final Closure
Upon final closure and reclamation of Climaxas described in the Reclamation Permit, Technical Revisions
and Amendments, impacted waters from the mine, ponded water on the TSFs, seepwater from TSFs and
OSFs, and storm water will be managed according to conditions of the CDPS Permit. This permit
acknowledges that surface water from Climax must meet effluent limitations prior to discharge.
EPP: Version R4 T-15 August 2018