Tessa Keller Opalach

Tessa Keller 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 a Class I railroad, following a derailment and alleged release of hazardous substances.
• Represents a materials science company in responding to government inquiry regarding the company’s manufacture and sale of PFAS.
• Represents a pharmaceutical waste stewardship entity in parallel enforcement defense and state court litigation regarding alleged compliance with California’s extended producer responsibility law for drugs and sharps.
• Represents an environmental remediation contractor defending mass tort and False Claims Act actions alleging data falsification at a Superfund site.

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

• University of California, Davis School of Law, 法律博士
• University of California, Davis, 文学学士

• 加利福尼亚州

• 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)