Chelsea E. O'Sullivan

O'sullivan, Chelsea E.

Chelsea O’Sullivan assists clients with a variety of environmental, infrastructure, and natural resource issues.  Chelsea’s practice includes regulatory advocacy regarding existing environmental regulations and ongoing rulemaking activity by the Environmental Protection Agency (EPA) and the Council on Environmental Quality, among other agencies. She provides guidance to clients on key environmental statutes, such as the Clean Water Act, the Comprehensive Environmental Response, Compensation and Liability Act, the National Environmental Policy Act, and the California Endangered Species Act, among others. 

Chelsea also helps clients evaluate the unique risks and challenges associated with the interaction of federal Indian law and environmental law in the siting and permitting of infrastructure projects. In the transactional space, she advises clients on environmental liability management strategies associated with the transfer and redevelopment of industrial, commercial, and residential properties and provides environmental due diligence counsel in a variety of transactional contexts.

Chelsea also maintains an active pro bono practice. In 2017 she won asylum for an unaccompanied minor. In 2018 she served as a Treanor Pro Bono Fellow at Bread for the City, helping survivors of domestic violence obtain civil protection orders against their abusers. Chelsea continues to take on civil protection order cases pro bono and helps senior citizens with their estate planning.

Chelsea earned a J.D. from University of Virginia School of Law, where she was the editor-in-chief of the Virginia Environmental Law Journal. She holds a B.S. in Environmental Science, summa cum laude, from Saint Mary’s College of California.




  • J.D. University of Virginia School of Law 2015
    • Editor-in-chief, Virginia Environmental Law Journal
    • Dillard Fellow
  • B.S. Environmental Science summa cum laude Saint Mary's College of California 2012

Bar Admissions

  • California
  • District of Columbia


  • Recognized as a Rising Star in the Washington, DC edition of Super Lawyers, 2020


Pro Bono

  • Treanor Pro Bono Fellow, Bread for the City, 2018
    • Helped survivors of domestic violence obtain civil protection orders
  • Won asylum for unaccompanied minor, 2017
  • Continues to pursue civil protection orders and assists senior citizens with estate planning