A leader of the firm’s natural resources practice, Deidre is lauded in Chambers USA, 2016 as “extremely capable,” “very familiar with the regulations and agencies,” and capable of giving clients “good insight into getting an expeditious outcome.”

Deidre focuses exclusively on environmental, energy and administrative law, representing clients on permitting, compliance and litigation relating to the Clean Water Act (CWA), the Endangered Species Act (ESA), the National Environmental Policy Act (NEPA) and other environmental statutes. She frequently counsels clients on administrative rulemaking and policy, providing regulatory clarifications when necessary, and drafting federal and state legislation on a myriad of intricate issues. She is also known for negotiating and obtaining permits for complicated energy and development projects.

Her clients include development companies, oil and natural gas pipelines, electric utilities, agricultural interests, state and local agencies, and various trade associations.

Prior to entering private practice, Deidre served as assistant general counsel of the Army at the Pentagon, advising the secretary of the Army on environmental and land use issues involving the Corps of Engineers’ Civil Works and section 404 Regulatory program, and the Base Realignment and Closure (BRAC) program. Deidre has extensive experience with federal regulatory agencies, military departments and the US Department of Justice.

Relevant Experience

  • Advise several of the nation’s largest interstate natural gas pipelines on environmental permitting and siting matters, regulatory compliance, and litigation under the CWA, ESA, NEPA and other federal environmental laws.
  • Advise liquid natural gas and coal export developers on NEPA, ESA, and CWA permitting and regulatory approvals.
  • Advise electric utilities and other energy companies on permitting electric transmission and other structures across federal lands administered by the Bureau of Land Management (BLM), the National Park Service (NPS), the United States Forest Service (FS), the Fish & Wildlife Service (FWS), and the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEM).
  • Serve as lead counsel to a broad coalition of industry and agricultural associations on matters involving legislative and regulatory changes to the CWA.
  • Advised an interstate natural gas pipeline company on ESA, the Marine Mammal Protection Act (MMPA), the CWA and US Coast Guard requirements with respect to an offshore LNG facility and pipeline.
  • Advised an interstate natural gas pipeline company on the interplay between BOEM and and Corps of Engineers’ regulations on abandonment of offshore pipelines.
  • Advise major water utility on federal water supply authorities.
  • Counsel to one of the largest coal companies on precedential legal challenge to EPA veto authority under section 404(c) of the CWA.
  • Counsel to coalition challenging agency CWA guidance as violating the Administrative Procedure Act’s rulemaking requirements.
  • Obtained critical regulatory changes to streamline the Corps of Engineers’ section 404 permitting and NEPA compliance.
  • Expedited federal environmental permitting approvals for a 400-mile oil pipeline, successfully avoiding construction delays. 
  • Represent land developers on jurisdictional determinations, use of general permits, expedited permitting procedures, and mitigation requirements under section 404 of the CWA.
  • Advised an interstate natural gas pipeline company in a potential enforcement action under the ESA; reached successful settlement with the FWS.
  • Lead counsel for a coalition of industry and agricultural interests on various CWA and ESA cases at the United States Supreme Court, including Rapanos v. United States.
  • Prepare comments on EPA and Corps rulemakings under the CWA and FWS and National Marine Fisheries Service (NMFS) under the ESA.
  • Advise state and local governments and private entities on Corps of Engineers’ real estate and water resources development project authorities.
  • Assist local redevelopment authorities with obtaining federal approvals for the environmental cleanup and transfer of military property, including compliance with NEPA.


  • Member, American Bar Association

Awards & Recognition

  • 2017 Chambers USA Environment Law Firm of the Year
  • Listed as a Future Star in Litigation, District of Columbia, Benchmark Litigation, 2016
  • Recognized as a Leader in Environmental Law, District of Columbia, Chambers USA, 2014-2017
  • Selected as a Best Lawyers for Environmental Law, Best Lawyers in America, A description of the selection methodology can be found on Best Lawyers’ webpage.
  • Client Choice Award, Environmental–DC, International Law Office and Lexology USA & Canada, 2014
  • Named among the Top Lawyers for Environmental Law, Washingtonian magazine, 2009 – present
  • Meritorious Service Medal, General Counsel of the Army, 2000
  • Army Commendation Medal, Assistant Chief of Staff of the Army, 1999