Mary Ellen Ternes

Mary Ellen Ternes

Earth & Water Law LLC

Recognized since 2007

Oklahoma City, Oklahoma

Practice Areas

Administrative / Regulatory Law

Environmental Law

Litigation - Environmental

Lawyer of the Year Badge - 2020 - Administrative / Regulatory Law Lawyer of the Year Badge - 2019 - Environmental Law Lawyer of the Year Badge - 2016 - Environmental Law Lawyer of the Year Badge - 2011 - Environmental Law
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Mary Ellen Ternes focuses her practice on environmental law, including environmental permitting, compliance strategies, enforcement defense, and state and federal litigation, as well as corporate disclosures and transactions. With a background in chemical engineering and hazardous waste remediation and combustion permitting, she specializes in air quality as well as hazardous waste issues.

Mary Ellen provides strategic counseling regarding complex legal and scientific issues arising in air permitting, including New Source Review (NSR), Title V, New Source Performance Standards (NSPS), and National Emission Standards for Hazardous Air Pollutants (NESHAPs), regulatory interpretation and applicability, compliance and enforcement resolution. She also advises regarding hazardous waste permitting, interpretation and enforcement matters, including generation, classification, exemptions, treatment and disposal issues, including corrective action and risk-based remediation, as well asToxic Release Inventory (TRI) reporting pursuant to Emergency Planning and Community Right to Know Act and underground storage tank regulation. She assists clients with water quality permitting and discharge regulation, including wetlands and stormwater issues, as well as Safe Drinking Water Act permitting and compliance.

Mary Ellen also maintains a very active transaction and voluntary cleanup practice, counseling clients regarding “All Appropriate Inquiry,” post-closing duties and disclosures.

Prior to entering law school, Mary Ellen applied her chemical engineering degree in chemical release emergency response, remediation, and chemical waste treatment, in her work for the U.S. Environmental Protection Agency (EPA) and industry. For EPA, she was an On-Scene Coordinator (OSC) ("commander on the scene" of a chemical release), a federal project and contract officer in emergency response and response action site characterization/remediation, and then she was a hazardous waste incinerator permit writer in Resource Conservation and Recovery Act (RCRA) incinerator permitting. She left the EPA to join industry, working as an environmental project officer for a commercial hazardous waste incineration company overseeing RCRA, Toxic Substances Control Act and Clean Air Act permitting, compliance and audit activities. During law school, she worked as a law clerk for the EPA Office of General Counsel Air and Radiation Division.

With her unique combination of education, training and experience in the fields of chemical engineering and environmental law, Mary Ellen has served in various leadership and liaison roles between the American Institute of Chemical Engineers (AIChE), the American College of Environmental Lawyers (ACOEL), and the American Bar Association (ABA), to better integrate law and policy with science and engineering.

She is a frequent author and speaker on environmental issues, particularly as it relates to improving applied science-based policy. Through her leadership roles within the ACOEL, ABA and AICHE, she frequently provides continuing legal and policy education on science-based policy and legal developments and strategic solutions.

Mary Ellen has contributed to the ABA’s Clean Air Act Handbook (Chapter 6: New Source Review; co-authored with Bernard F. Hawkins, 2nd, 3rd and 4th editions), and co-authored the Air Pollution Control Technology Handbook, a chemical engineering text book (2nd ed., CRC Press). She also contributed to the ABA’s Nanotechnology Environmental Law, Policy and Business Considerations (Ch. 4: Clean Air Act and Nanotechnology; ed. Lynn L. Bergeson), and the LexisNexis Global Climate Change Special Pamphlet Series, (EPA’s Mandatory Greenhouse Gas Reporting Rule; ed. Bradley M. Marten). In 2007, her comprehensive publication titled "Basic Practical in Nanotechnology" won a competitive, peer-reviewed Best Paper Award at the ABA’s Section of Environment, Energy and Resources Fall Meeting. .

Since its debut in 2004, the International Who's Who of Environment Lawyers has named Mary Ellen to its prestigious list of pre-eminent environmental lawyers worldwide each year. In 2008, Mary Ellen was granted early election as a Fellow of the American College of Environmental Lawyers, a professional association of private and public sector environmental lawyers recognized by their peers as pre-eminent in their field, and has served as Secretary. In 2018, Mary Ellen was also elected a Fellow of the American Institute of Chemical Engineers. Her achievements have also earned her inclusion in Chambers USA Guide to America's Leading Lawyers for Business (energy and natural resources: environment), The Best Lawyers in America (environmental law, environmental litigation and administrative law) and Oklahoma Super Lawyers, in which she was named to its list of “Top 25 Women Oklahoma Super Lawyers." She was also named Best Lawyers' Oklahoma City "Lawyer of the Year" for Environmental Law in 2011, 2016 and 2019, an honor only given to a single lawyer in each legal specialty in each community.

Contact & Links


  • 5030 North May Avenue, Suite 324
    Oklahoma City, OK 73112


  • University of Arkansas at Little Rock, graduated 1995
  • Vanderbilt University , graduated 1984

Bar Admissions

  • Oklahoma, Oklahoma Bar Association
  • South Carolina, South Carolina Bar
  • District of Columbia, The District of Columbia Bar
  • Arkansas, Arkansas Bar Association


  • American College of Environmental Lawyers - Fellow, Secretary 2017-2018
  • American Bar Association, Business Law Section - Chair, Environmental Committee
  • American Institute of Chemical Engineers - Fellow, and Chair, Legal Developments Subcommittee, Public Affairs and Information Committee
  • Vanderbilt University School of Engineering, Chemical and Biomolecular Engineering - External Affairs Committee

Regulatory Agencies

  • Environmental Protection Agency (EPA) - Office of General Counsel

Earth & Water Law LLC
Washington, District of Columbia

4 The Best Lawyers in America® awards

Full Firm Profile

Lawyer of the Year Badge - 2020 - Administrative / Regulatory Law Lawyer of the Year Badge - 2019 - Environmental Law Lawyer of the Year Badge - 2016 - Environmental Law Lawyer of the Year Badge - 2011 - Environmental Law

Named "Lawyer of the Year" by Best Lawyers® for:

  • Administrative / Regulatory Law, Oklahoma City (2020)
  • Environmental Law, Oklahoma City (2019)
  • Environmental Law, Oklahoma City (2016)
  • Environmental Law, Oklahoma City (2011)

Recognized in The Best Lawyers in America® 2022 for work in:

  • Environmental Law
  • Litigation - Environmental
  • Administrative / Regulatory Law

Special Focus

  • Administrative/Regulatory
  • Clean Air Act
  • Clean Water Act
  • Climate Change
  • Counseling
  • COVID-19
  • Defendants
  • Environmental Cleanup
  • Environmental Permitting
  • Litigation
  • RCRA/Hazardous Waste
  • Solid Waste
  • Superfunds/Environmental Remediation


  • Fellow, American College of Environmental Law
  • ABA SEER Best Paper Award, for "Basic Practical in Nanotechnology", 2007
  • International Who's Who of Environment Lawyers

"Mary Ellen came in at a time of doom and gloom. She was able to get both state and federal entities to back off enforcement action and discuss meaningful resolution to a joint problem. The end result was a new compliant permit and a positive relationship with both state and federal."

- Gary Sackman (W&W Steel)

"It was extremely convenient having a degreed chemical engineer as our attorney. It saved countless hours of time and trouble trying to explain how pollutants are calculated."

- Kathy Mershon (SGL Carbon)

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