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.
Acting Principal Deputy Assistant Secretary, Office of Environmental Management
Joel B. Bradburne
Joel B. Bradburne serves as the Acting 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
-
The Office of Environmental Management participated in the 52nd annual Waste Management Symposia from March 8-12 where Assistant Secretary Tim Walsh introduced an inspiring new vision for EM. March 17, 2026March 17, 2026
-
Hanford leadership joined industry partners and federal officials at the Waste Management Symposium to discuss the site’s cleanup progress and the path forward for one of the nation’s most complex environmental remediation missions. March 17, 2026March 17, 2026
-
Successful cleanup and reuse efforts underway at the Oak Ridge, Paducah, and Portsmouth sites are vividly illustrating the Office of Environmental Management’s ability to successfully deliver its vision of nuclear restoration and revitalization across the DOE complex, federal and contractor leaders said. March 17, 2026March 17, 2026
-
U.S. Department of Energy Office of Environmental Management Assistant Secretary Tim Walsh recently joined U.S. Reps. Chuck Fleischmann and Susie Lee for the first U.S. House Nuclear Cleanup Caucus event of the year. February 17, 2026February 17, 2026
-
More than 90 officials from local, state and tribal governments recently took part in a virtual meeting where U.S. Department of Energy Office of Environmental Management Assistant Secretary Tim Walsh addressed five national intergovernmental groups with representatives located near cleanup sites who provide community perspectives to EM leadership. February 3, 2026February 3, 2026
-
Assistant Secretary Tim Walsh welcomed U.S. Secretary of Energy Chris Wright to the Hanford Site.December 9, 2025