Duncan is the Chair of the Firm’s Air and Waste Practice Group. He has more than 30 years of experience in environmental regulatory law in Texas. He focuses his practice on representing businesses and governmental subdivisions in permitting, enforcement, and rulemaking issues before the Texas Commission on Environmental Quality (“TCEQ”) and the Environmental Protection Agency.

Prior to joining Lloyd Gosselink, Duncan was the General Counsel to the TCEQ, providing legal advice and counsel to the three Commissioners appointed by the Governor on permitting, enforcement and rulemaking matters. He also managed the TCEQ’s litigation.

Duncan is a former Administrative Law Judge for the Texas Water Commission, and is a guest lecturer at the U.T. School of Law.


  • Practice Areasopen

  • Professional Licenses and Educationopen


    • Board Certified in Administrative Law by the Texas Board of Legal Specialization (1990)
    • Admitted to State Bar of Texas (1985)
    • J.D., Texas Tech University School of Law (1984)
    • B.B.A., Texas Tech University (1981)


  • Representative Experienceopen


    • Oral argument and briefing before the Texas Court of Appeals and the Texas Supreme Court
    • Permitting of largest landfill expansion in Texas
    • Permitting Greenfield sites for new landfills
    • Successfully defending numerous clients in TCEQ environmental enforcement matters
    • Negotiating Agreements with opposing parties and local governments on environmental issues
    • Air Quality Permitting of rock crushers and frac sand processers
    • Successfully advocating for TCEQ rule amendments
    • Assisting clients with Texas Risk Reduction Program remediations
    • Assisting clients with TCEQ Voluntary Clean-up Program approvals
    • Assisting clients with municipal setting designations
    • Advising clients on waste management matters
    • Securing rate increases and CCN amendments for water and wastewater utilities


  • Publications and Presentationsopen


    • Texas Tech School of Law, “TCEQ Enforcement Process”
    • TWCA Water Law Conference, “TCEQ Enforcement of Edwards Aquifer Rules”
    • U.T. Water Law Seminar, “Water Reuse”
    • Advanced Administrative Law Conference, “Rulemaking Issues”
    • Texas Aggregate and Concrete Association Conference, “TCEQ Permit Process”
    • Texas Rural Water Association, “PUC Rate Appeals”


  • Professional Associations and Membershipsopen


    • State Bar of Texas
    • Austin Bar Association, Environmental Law Section
    • American Bar Association
    • Industry Council for the Environment – Legislative Committee Chair


  • Personal Profileopen


    Duncan and his wife, Jo Betsy have two sons: Reed, a Red Raider and Cole, a Longhorn. An avid sports fan, Duncan coached his sons in the youth league and AAU basketball for 15 years. On weekends you will likely find him at UT games, playing golf and cooking on his backyard grill.  He and Jo Betsy enjoy playing fetch and swimming with their yellow lab Daisy.