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 Principal 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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As 1,200 government and industry leaders from 35 states and four countries discussed advances in the nuclear industry and what’s needed to maintain momentum during a conference here, Assistant Secretary of Environmental Management Tim Walsh made his message clear: The Office of Environmental Management is creating opportunities for the private industry and paving the way for big things. August 11, 2026August 11, 2026
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U.S. Secretary of Energy Chris Wright and Assistant Secretary of Environmental Management Tim Walsh joined industry leaders and local, state and national representatives to announce the development of a new American Energy Hub at the Paducah Site. August 4, 2026August 4, 2026
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Assistant Secretary of Environmental Management Tim Walsh and his leadership team recently visited the EM Los Alamos Field Office, seeing firsthand the progress achieved for the Los Alamos National Laboratory legacy cleanup. August 4, 2026August 4, 2026
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Pacific Northwest National Laboratory showcased its science-based solutions to the nation’s most complex nuclear waste cleanup challenges during Assistant Secretary of Environmental Management Tim Walsh’s first visit to the laboratory. August 4, 2026August 4, 2026
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Oak Ridge Office of Environmental Management Manager Erik Olds and Savannah River Operations Office Manager Edwin Deshong joined U.S. Department of Energy Under Secretary for Science Darío Gil for a U.S. House Nuclear Cleanup Caucus event. July 28, 2026July 28, 2026
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Assistant Secretary of Environmental Management Tim Walsh and his leadership team visited the Idaho Cleanup Project. July 21, 2026July 21, 2026