Tessa Opalach

Tessa Opalach counsels clients in complex environmental litigation, including class actions and civil and criminal government enforcement actions. She is well versed in handling responses to government investigations brought by federal and state regulators, including the US Environmental Protection Agency and the US Department of Justice. Tessa also advises clients on environmental, social and governance topics.

Prior to joining Mayer Brown, Tessa practiced at an international law firm where she also focused on environmental litigation and enforcement. After law school, Tessa clerked for the Honorable Nanette K. Laughrey of the US District Court for the Western District of Missouri.

• Represents an environmental remediation contractor defending mass tort and False Claims Act actions alleging data falsification at a Superfund site.
• Represents an engineering company in criminal investigations of alleged violations of the Resource Conservation and Recovery Act.
• Represented a national healthcare company in criminal investigations of alleged violations of the Clean Air Act, resulting in a declination.*
• Represented a railroad in enforcement and class action litigation following a derailment and alleged release of hazardous substances.*

• Best Lawyers: Ones to Watch in Environmental Law (2025, 2026)

• University of California, Davis School of Law, JD
• University of California, Davis, BA

• California

• Co-Chair for the Environment, Land Use and Real Estate Section of the Bar Association of San Francisco (2024-2025)
• Liaison to the Environmental Law Section of the Bar Association of San Francisco (2024)