We have assembled a team of accomplished and successful experts in the mining industry who are committed to achieving the goals of the company and successfully developing the communities in which the company has mining operations.

  • Mike Bunch – Executive Vice President/Chief Operating Officer
  • David Tretbar - Vice President of Exploration and Mineral Resources
  • Satoshi Naruse - Vice President of Business Development/Secretary and Treasurer
Mike Bunch

Mike Bunch

Executive Vice President/Chief Operating Officer

As the Executive Vice President and Chief Operating Officer (COO), Mike Bunch reports to the President & Chief Executive Officer and is responsible for the company's optimization of day-to-day operating activities, including safe production; expense, cost and margin control; and financial, legal, quality, and environmental management. He directs the short-term and long-range planning and budget development to support strategic business goals and is responsible for execution of operating policies to support overall company goals and objectives.

Career Profile

Mike Bunch is a registered professional mining engineer (Arizona) with more than 25 years of domestic and international mining & mineral process experience including the successful development and startup of a world class copper mine (El Abra, Chile) and a world class lead-zinc-silver mine (San Cristobal, Bolivia).

Prior to joining Summit Mining International in October 2009, Mr. Bunch was Vice President and General Manager of the San Cristobal Mine where he implemented a business management system that moved the project from bankruptcy to profitability in less than a year. San Cristobal became the first mine in the world to achieve simultaneous triple international certification (ISO 9001, ISO 14001, & OHSAS 18001).

Mr. Bunch's professional experience includes senior management positions with both Cyprus Amax and Phelps Dodge at El Abra, Chile (1995), Sierrita, Arizona (1998), Bagdad, Arizona (2000), and La Candelaria, Chile (2003).

From 1989 to 1994, he held multiple operating, maintenance, engineering and project development roles with Cyprus Amax (Sierrita and Twin Buttes, Arizona).

He began his mining career in 1978 at Newmont's underground Magma Mine (San Manuel) where he supervised both operations and development areas including draw and haulage, concrete, timber repair, drifts and raise stations, grizzly drifts, raises, and undercuts.


  • Bachelors of Science Mining Engineering, University of Arizona, 1978
  • Masters of Business Administration, University of Phoenix, 1992
  • Registered Professional Mining Engineer, State of Arizona License #47663, 2008
David Tretbar

David Tretbar

Vice President, Exploration and Mineral Resources

As the Vice President, Exploration and Mineral Resources of Summit Mining International, David Tretbar is responsible for developing exploration programs, implementing exploration and resource development strategies, and providing technical support in all aspects of mine and mill production. The responsibilities include oversight of the exploration and mine geology programs at Minera San Cristobal in Bolivia, project due diligence for strategic alliances and joint ventures, and executive support functions within Summit Mining and parent company Sumitomo Corporation.

Career Profile

Mr. Tretbar has wide-ranging experience in surface and underground exploration, resource modeling, mine development and production, laboratory operations, mineral analysis, process metallurgy, and project management. Prior to joining Summit Mining International in 2010, Mr. Tretbar held a number of operational management level positions, including Chief Resource Geologist for Apex Silver at Minera San Cristóbal and both Mill Manger and Manager Engineering & Geology for the Ashdown Molybdenum Mine in Nevada.

Mr. Tretbar has worked as an underground mine geologist at several Nevada gold mines, including 4 years at the Getchell Mine where he conducted his Master’s degree research on geochemistry and mineralization of the deposit. He later spent 3 years as process mineralogist for Barrick Gold Corporation at the Goldstrike Operation. From 2004 to 2007 Mr. Tretbar was senior exploration geologist for Alamos Gold at their Mulatos Mine in Sonora, Mexico. While there he designed and directed construction of 2000m of exploration tunnels and managed near-mine exploration programs. At the narrow-vein, high-grade Ashdown Molybdenum Mine in northern Nevada, David simultaneously managed the molybdenum flotation plant and designed the underground ramp access and stope sequence mining plans.


  • B.S. Geology, Northern Arizona University, 1995
  • M.S. Geochemistry, University of Nevada Reno, 2004


  • Certified Professional Geologist – American Institute of Professional Geologists
  • Registered Professional Geologist – Arizona

Satoshi Naruse