Kent Mayo

Kent Mayo handles a wide variety of environmental matters, with a focus on environmental litigation and enforcement defense and strategic regulatory compliance. He represents clients in toxic tort and class action litigation arising from environmental issues. His litigation work also includes serving as lead counsel in multiple enforcement actions brought by the United States, states and citizen groups under the Clean Air Act and other statutory programs.

In the regulatory sphere, Kent counsels clients on rulemakings and regulatory compliance and works with clients to develop broad strategies for working with regulators. He assists clients in compliance investigations and audits addressing multiple statutory schemes, including the Clean Air Act, RCRA (coal ash) and the SDWA. Kent also works with clients to prepare for and respond to environmental crisis events, including working with responders and regulators such as EPA, Chemical Safety Board and state agencies to protect the client's interests.

Kent previously worked as a trial lawyer in the Environmental Enforcement Section of the U.S. Department of Justice, where he led teams in complex environmental litigation, settlement negotiations and mediations across a broad range of civil environmental actions, including cases involving Clean Water Act and Clean Air Act violations and cases arising under CERCLA's remedial, cost recovery and natural resource damages provisions.

Litigation and Enforcement Defense

• Representation of water provider as national counsel defending class action litigation filed following chemical spill impacting water supplies
• Representation of corn products company in class action litigation regarding air-based nuisance claims
• Representation of water provider regarding class action lawsuit arising from water main break
• New Jersey v. RRI Energy Mid-Atlantic Power Holdings, LLC - Litigation counsel representing power producers in federal Clean Air Act citizen suit litigation in Pennsylvania
• United States v. Louisiana Generating LLC - Lead litigation counsel representing power producer in defense and settlement of USDOJ Clean Air Act NSR lawsuit
• Representation of petroleum refiner in negotiations regarding EPA enforcement of consent decree requirements
• WildEarth Guardians v. Public Service Company - Lead litigation counsel representing power producer in defense of Clean Air Act citizen suit alleging opacity violations
• Representation of utility in negotiation of settlement of alleged NSR claims regarding sulfuric acid mist emissions
• WildEarth Guardians v. Public Service Company - Litigation counsel defending power producer against Clean Air Act citizen suit alleging MACT violations; received favorable verdict in federal district court; dismissal upheld by Tenth Circuit Court of Appeals
• United States v. Kentucky Utilities Company - Lead litigation counsel representing utility in defense and settlement of USDOJ Clean Air Act NSR and NSPS lawsuit
• Sierra Club v. Dayton Power & Light - Litigation counsel for three co-owners of an Ohio power plant in defense and settlement of lawsuit alleging Clean Air Act violations
• Representation of power producer in challenge to Title V permit by citizen groups in Tenth Circuit Court of Appeals
• Representation of major engine manufacturer in dispute with United States regarding settlement compliance in federal district court and D.C. Circuit
• Complex technical settlement with a municipal entity requiring substantial injunctive relief under the Clean Water Act arising from unpermitted sewer overflows
• Clean Air Act settlement with a major petroleum refiner requiring injunctive relief and civil penalties with respect to five refineries, including court defense of the settlement against citizen challenges
• Lead counsel on DOJ/EPA case team presented with the EPA National Superfund Enforcement “Team of the Year” Award for representation of the United States’ enforcement and defensive interests in a multiparty CERCLA action

Permitting and Compliance

• Advise utilities on compliance with CCR rule and Clean Water Act ELGs
• Counsel power producer groups on litigation and enforcement issues
• Representation of utility in defense to administrative challenges to construction permit issued for new coal-fired generating unit in Kentucky
• Representation of power producer in permitting actions and administrative and state judicial permit challenges to construction permit for $1.3 billion coal-fired generating unit in Colorado
• Assisted client in defending challenges to Title V permit and responding to EPA statements on issues of first impression regarding PM2.5 monitoring
• Advise various clients on NSR and Title V compliance issues, as well as compliance with changing regulatory requirements under national regulatory programs including the EGU MACT, Boiler MACT, Clear Air Interstate Rule, Cross-State Air Pollution Rule, SSM Policy and greenhouse gas regulations

Recognized as a "Leading Lawyer" by The Legal 500 U.S., 2020

J.D., Washington University School of Law 1995
Order of the Coif
Editor in Chief, Washington University Law Quarterly

A.B., Political Science, Duke University 1990
cum laude

District of Columbia Bar

State Bar of Colorado

United States Court of Appeals for the District of Columbia Circuit

United States Court of Appeals for the Tenth Circuit

United States District Court for the District of Columbia

United States District Court for the District of Colorado

American Bar Association, Environment, Energy and Resources Section