Assistant Secretary, Office of Environmental Management
Timothy J. Walsh
Timothy J. Walsh became the Senate confirmed Assistant Secretary for the Department of Energy's Office of Environmental Management on Oct. 23, 2025. He provides leadership for the safe cleanup of the environmental legacy brought about from eight decades of nuclear weapons development and government-sponsored nuclear energy research.
Principal Deputy Assistant Secretary, Office of Environmental Management
Joel B. Bradburne
Joel B. Bradburne serves as the Principle Deputy Assistant Secretary for the Office of Environmental Management (EM). In this role he works to enable the safe and successful execution of the EM mission while providing management and oversite of activities, operations, and program integration across the Department of Energy field sites.
Chief Operating Officer, Office of Environmental Management
David Brunnert
David Brunnert serves as Chief Operating Officer for the Office of Environmental Management (EM) at the U.S. Department of Energy. In this role he leads strategic operations and mission critical initiatives to drive execution and performance across the EM enterprise.
Associate Principal Deputy Assistant Secretary for Field Operations, Office of Environmental Management
Gregory Sosson
Gregory Sosson is the Associate Principal Deputy Assistant Secretary for Field Operations for the Office of Environmental Management (EM). He is responsible for developing strategies, policy, and guidance for the 15 EM field sites in support of the EM mission. He oversees nuclear operations, safeguards and security, and technology development.
Associate Principal Deputy Assistant Secretary for the Office of Regulatory and Policy Affairs, Office of Environmental Management
Jack Zimmerman
Jack Zimmerman began serving as the Acting Associate Principal Deputy Assistant Secretary for the Office of Regulatory and Policy Affairs within the US Department of Energy’s Environmental Management Office in October 2025. His portfolio includes infrastructure disposition, subsurface closure, regulatory compliance, waste and materials management and packaging and transportation.
Associate Principal Deputy Assistant Secretary for the Office of Corporate Services, Office of Environmental Management
Steve Trischman
Steve Trischman serves as the Associate Principal Deputy Assistant Secretary for the Office of Corporate Services, and as the Acting Deputy Assistant Secretary for Resource Management, within the US Department of Energy’s Environmental Management Office. His portfolio includes budget and planning, information systems, workforce management, acquisition and contract management and project management.
Field Managers
Leadership News
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In his first trip to Oak Ridge last week, Assistant Secretary for Environmental Management Tim Walsh witnessed firsthand the reach and impact of the U.S. Department of Energy’s cleanup mission. April 14, 2026April 14, 2026
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The Moab Uranium Mill Tailings Remedial Action Project celebrated a landmark milestone: removal of a cumulative 16 million tons of residual radioactive material and the complete disposal of the uranium mill tailings pile away from the Colorado River. April 14, 2026April 14, 2026
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Joel Bradburne and other members of the U.S. Department of Energy’s Office of Environmental Management leadership team visited the Idaho Cleanup Project. April 7, 2026April 7, 2026
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SB Energy, a SoftBank Group company, recently announced a unique public-private partnership to construct the world’s largest artificial intelligence data center on leased land at the U.S. Department of Energy’s Portsmouth Site. April 7, 2026April 7, 2026
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Powers AI Data CenterMarch 24, 2026