Mark Whitney, the Energy Department’s No. 2  nuclear-cleanup official, is leaving the agency for a private sector gig, his boss wrote in an internal memo that leaked Tuesday.

“It is with gratitude for his service that I share with you the news that Mark Whitney is leaving DOE to pursue an opportunity in the private sector,” Monica Regalbuto, assistant secretary for environmental management, wrote in the memo.

Whitney, an 11-year DOE veteran, has been principal deputy assistant secretary for environmental management since 2014. He will leave the agency in mid-October, according to the memo. Regalbuto did not say where Whitney would work post-DOE, and Whitney himself could not be reached for comment late Tuesday.

Whitney most recently oversaw a reorganization of the Environmental Management bureaucracy that brought the office’s active cleanup sites under direct management of a new headquarters-based field office czar.

Whitney was the department’s de facto spokesman for the reorganization, saying often in the waning months of his tenure the change would restore to the Office of Environmental Management a focus on the field sites that has been lacking in recent years.

Whitney, also a fond Washington Nationals fan, will be replaced on an acting basis by Sue Cange, manager of DOE’s Oak Ridge Site near Oak Ridge, Tenn.

A copy of Regalbuto’s memo was obtained by Weapons Complex Morning Briefing. The community interest group Energy Communities Alliance first broke news of Whitney’s departure Tuesday.