Dec 23 2010
Mines Management, Inc. (NYSE-Amex:MGN) (TSX:MGT) has announced the completion of a Preliminary Economic Assessment for the Company's wholly owned Montanore Silver-Copper Project located in the United States.
Results of the PEA illustrate that the economics of the project would be robust in today's cost and metals price environment and represents a solid economic foundation upon which to build. An NI 43-101-compliant technical report will be filed on SEDAR within 45 days.
A mine plan developed by Mines Management, Inc. ("MMI") was audited by Mine and Quarry Engineering Services, Inc. ("MQes") of San Mateo, California. Cost estimates were developed by MQes. The mine plan is based on a Measured and Indicated Mineral Resource of 81.5 million short tons of material grading 2.04 ounces per short ton ("opt") silver and 0.75% copper, and an Inferred Mineral Resource of 35.0 million short tons grading 1.85 opt silver and 0.71% copper at a cutoff grade of 1.0 opt silver, previously reported in an NI 43-101 Technical Report (October 2005) prepared by Mine Development Associates ("MDA") of Reno, Nevada. Mines Management's estimate of mineralized material reported pursuant to U.S. Securities and Exchange Commission rules in its annual report on Form 10-K for the year ended December 31, 2009, remain unchanged.
The PEA indicates a financially robust underground mine utilizing conventional grinding and flotation processing techniques at a nominal throughput of 12,500 short tons per day ("st/d"). At a 5% discount rate, a silver price of US$15.00 per ounce ("oz") and a copper price of US$3.10 per pound ("lb"), the project's pre-tax Net Present Value ("NPV") is indicated to be US$485 million with an internal rate of return ("IRR") of 17.4% on an unleveraged 100% equity basis.
Using metals prices as of November 17, 2010, of US$25.65/oz. silver and US$3.72/lb. copper, the project indicated a pre-tax NPV of US$1.323 Billion and IRR of 32.3%, at a 5% discount rate.
Commenting on the PEA, Company President and Chief Executive Officer Glenn Dobbs said, "This PEA is the culmination of analysis and engineering to optimize the mine plan. It indicates the Montanore mine plan may be quite profitable in today's commodity environment and could operate at metals prices significantly below current levels. The favorable economics indicated in the PEA at this early stage of development underscore the strong case for advancement through the final steps of the permitting process and completion of the subsequent underground drilling and evaluation program for which we have completed surface construction and initiated underground preparations."
All dollar amounts in this release are stated in U.S. currency, unless otherwise stated. The disclosure set forth below is derived from the PEA unless otherwise expressly noted. Average estimates are assumed over the 15-year life of mine ("LOM") unless otherwise stated.
The Montanore Silver-Copper Project is 100% controlled by Mines Management, Inc., subject to a $0.20-per-ton production royalty. The Montanore deposit underlies portions of Lincoln and Sanders Counties in northwestern Montana. The Company controls its mineral rights for the deposit by virtue of extralateral rights projecting from patented apex claims.
The mineralized zones crop out at the surface and extend down dip at least 12,000 ft. to the north-northwest. The mineralization is open ended in the down-dip direction. Mineralization occurs in two sub-parallel horizons separated by an unmineralized zone. The average dip is just over 15 degrees. The deposit is controlled on one side to the southwest by a fault. The width of the main horizon in plan view is controlled by property boundaries to a maximum of 2,000 ft. The average thickness for each of the two horizons is 35 ft., depending upon cutoff.
During mining, the deposit would be accessed through three declines, each extending approximately 14,000 to 17,000 feet from the east, with processing facilities at the surface.
The project is being advanced under permits approved by the state of Montana in 1993. Surface facilities have been constructed in preparation for an underground evaluation and drilling program that will support a feasibility study. The project is currently undergoing a NEPA process, following which the Company plans an underground evaluation program to support a feasibility study.
The PEA is based on an underground mining operation, utilizing conventional grinding and flotation processes. The deposit would be bulk mined 350 days per year and utilize an inclined room and pillar mining method producing at a nominal rate of 12,500 short tons per operating day, although the mine is being permitted for a throughput of up to 20,000 short tons per day.
Over the 15-year mine life, an estimated 59 million short tons of process feed would be treated at average grades of 1.88 ounces silver per ton and 0.72% copper, yielding a total of 96 million ounces of silver and 767 million pounds of copper. Above average feed grades of 2.26 opt silver and 0.84% copper would be mined in the first four years.
Under the current mine plan, forty foot wide topslices would be mined on strike below the hanging wall contact. Connection drifts between adjacent top cuts would be mined following the hanging wall contact at a gradient of 15% forming obliquely angled permanent stope pillars. Mineralization below the topslice would be mined by a longhole bench. Based on rock mechanics study recommendation, the Company plans that a minimum interbed thickness of 50 feet will be maintained between the mining zones.
Mining at Montanore is planned to be highly mechanized through the use of large high-tech mining equipment including modern load-haul-dump units ("LHD") and trucks, and computer-controlled drilling jumbos. Material flow would consist of broken ground being hauled from the faces by LHD and truck to grizzlies centrally located in each mining panel. The material would discharge from the rock pass, via an apron feeder, onto the pre-crusher conveyor system to the crusher. Primary crushing would occur underground. The process feed is then transported via conveyor to the surface for grinding and flotation.
The deposit is open down dip to the northwest. Diamond drilling in the northern area of the deposit has suggested a third mineralized bed might exist. Insufficient data was available to include this mineralization in resources, however there is potential for significant expansion of the resource.
METALLURGY AND PROCESSING
The process flowsheet selected for investigation at the Montanore project uses conventional grinding and flotation techniques and is broadly similar to that used at copper projects elsewhere. Process development for the project has concentrated on initial validation of a basic flow sheet involving crushing, SAG and ball mill grinding, bulk sulfide flotation, concentrate regrinding, followed by three cleaner stages. Results have been encouraging, with no fatal flaws encountered that would require a fundamental change in the process.
Major infrastructure for the project will include a 230kV electrical transmission line approximately 17 miles in length, access road and bridge improvements and water treatment facilities, among other items.
Capital costs are based on run of mine ore delivered to the underground feeders, primary crushing, coarse feed conveying, process plant and ancillary facilities as defined in the equipment list contained in the 2006 preliminary capital and operating cost study.
Other capital project costs have been included for access roads and bridges, a temporary 34.5kV power line, tailing, 230kV power line, mine development, equipment and infrastructure, as well as owners environmental and working capital.
The initial capital cost for the Montanore project to treat 12,500 st/d of material is estimated at US$552.3 million (+/-35% accuracy). Ongoing and replacement capital costs and closure capital are estimated to be an additional US$217.9 million over the life of mine. Costs are expressed in 2nd quarter, 2010 U.S. dollars.
- Permitting: Continue with completion of permitting process. Remaining steps include completion of Supplemental Draft Environmental Impact Study ("EIS"), Final EIS, and Record of Decision.
- Evaluation drilling program: Complete development drifting and evaluation program, including 50,000 feet of diamond core drilling. The program would confirm the resource, geological structure and deposit geometry in the areas of the planned infrastructure and first mining panels. It would also furnish sample material for metallurgical testwork, geotechnical and geometallurgical modeling. This would provide information needed to advance the engineering development of the project.
- Feasibility study: Data from evaluation program will support completion of final feasibility study.
PREPARATION OF PEA AND NI 43-101 TECHNICAL REPORT
The PEA has been prepared with audit and cost estimation by MQES, and input from Hatch Engineering, MMI, MDA, McIntosh Engineering, Klepfer Mining Services, among others.
A Technical Report published in conformance with National Instrument 43-101 will be filed on SEDAR within 45 days of this press release and will include a summary of the PEA.
The PEA was prepared under the supervision of Mr. Chris Kaye, and Mr. Geoffrey Challiner, each of whom are "Qualified Persons," as such term is defined in National Instrument 43-101, and each have read and confirmed that this news release fairly and accurately reflects the technical contents of the PEA report. Mr. Steve Ristorcelli, with Mine Development Associates ("MDA"), is a "Qualified Person," as such term is defined in National Instrument 43-101, and has reviewed the information with respect to the reported silver and copper resources contained in this release.
The Montanore deposit was discovered in 1983 by U.S. Borax & Chemical, which conducted approximately 70,000 feet of diamond core drilling. Mines Management's mineral claims, which were leased to the operator, overlapped a portion of the deposit. In 1988, title to the deposit was sold to a consortium led by Noranda Minerals of Canada. Noranda conducted numerous activities including completion of project permitting by 1993, 14,000 feet of development of an evaluation adit, compilation of surface claims and patenting of mineral claims, among other things. In 2002, Noranda withdrew from the project due to low metals prices at the time, and quitclaimed title to the deposit to Mines Management in accordance with the lease agreement. In 2006, Mines Management acquired Noranda's U.S. operating companies, along with title to patented lands including the portal site to the adit and project permits, and initiated excavation of the portal and reconstruction of site infrastructure in preparation for resuming the evaluation drilling program. In 2005, Mines Management initiated the NEPA process, and the Company is currently working toward completion of supplemental draft and final environmental impact studies.
Source: Mines Management, Inc.