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Thierry is a member of the Environmental Practice Group. He helps clients resolve air, soil, and groundwater disputes. He has significant experience litigating claims under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the Resource Conservation and Recovery Act (RCRA), the Clean Water Act, and other State and Federal statutes and common law.

Thierry has achieved successful results for his clients–both public and private sector entities–in a variety of complex environmental, land use, construction, and eminent domain matters. In addition, he assists clients on natural resources issues involving water, oil and gas interests, air and water permitting and violations, including the National Pollutant Discharge Elimination System (NPDES) and Title V of the Clean Air Act.

Thierry has an active land use practice, where he advises clients on a broad range of permitting, zoning, California Environmental Quality Act (CEQA) and National Environmental Policy Act (NEPA) matters, and eminent domain expertise.

Other Info About Thierry


Legal Work Highlights

Represented a developer of an eight-story condominium project in a “brownfield” area in a CEQA petition—getting a dismissal via a motion challenging a writ’s substantive claims, targeted aggressive response resolved in a court dismissal a month into the lawsuit.

Defended a metal parts stamping company in a state lawsuit brought by neighboring business alleging PCE/TCE contamination from our site to theirs. Argued the neighboring site was an enormous source of PCE/TCE contamination before the State Regional Water Quality Board—turning its attention to the neighboring business. Opposing counsel then agreed to toll the state lawsuit.

Represented a public entity seeking to expand their wastewater treatment facility by defeating a challenge brought on by an environmental group alleging that the wastewater treatment facility should heat its reclaimed water discharges into an adjacent stream to protect a protected local fish species’ spawning area. The environmental group alleged that the reduced loss of this fish species was because of chilled wastewater releases impacting spawning eggs. Thierry used legal and scientific evidence tying species loss to heron and small mouth bass predation and not his client’s wastewater discharges.


Law School

University of Notre Dame Law School, J.D., 1991

Undergraduate School

University of California, Riverside, B.A. Political Science, 1982

Bar Memberships

Thierry is licensed to practice in the following state(s):

California, 1992

Professional Affiliations

Professional Affiliations & Memberships

Association of Business and Trial Lawyers 

Orange County Bar Association, Environmental Law Section 


Civic Activities

Civic & Charitable Organizations

Environmental Liabilities and Penalty Reporter, Editor 

Global Environmental Legacy Foundation, Executive Director 

Orange County Big Brothers, Big Brother 

Firm Committees

Thierry serves or has served in the following leadership role(s) at Frost Brown Todd:

Sustainability Committee, Member


Thierry was invited to speak at the following events:

“Is it Really Still Possible to Close Environmental Cases in California?,” Frost Brown Todd and Murex Environmental, Inc. Technical and Legal Seminar, May 2023

Major Publications

Thierry is an author or contributor to the following publications:

Author, “The Future of Climate Policy & Corporate Accountability,” Practical Guidance: ESG, Professional Perspective, Bloomberg Law, May 2024

Host, Essential Environmental with Thierry Montoya, Audio Podcast Series, 2022-Present

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