Patrick Traylor, a former U.S. Environmental Protection Agency administrator who focused on Clean Air Act civil enforcement, joined Vinson & Elkins on Tuesday as a partner in Washington, D.C.

Prior to his two-and-a-half years at the EPA, Traylor spent 20 years at Hogan Lovells, where he was a partner in the firm's environmental practice, also based in Washington.

Traylor was the principal negotiator for the EPA in the recent Fiat Chrysler diesel engine emissions case that ended earlier this year with a settlement valued at about $800 million.