Mayer Brown’s Environmental team offers innovative solutions to clients facing litigation, navigating enforcement concerns, implementing regulatory compliance programs or tackling issues that arise in transactions. Our global presence—frequently representing clients in cross-border disputes and transactions throughout the Americas, Asia, Europe and the Middle East—is significantly supplemented by our deep experience litigating major cases in state and federal courts across the United States and providing preeminent appellate services.

We represent clients in such high-stakes matters as emerging torts relating to greenhouse gas emissions; site-based mass tort claims, such as the Flint, Michigan, water cases and PFAS litigation; issues of first impression under the Clean Water Act; challenges to US EPA regulations under the Clean Air Act; criminal environmental prosecutions and complex environmental cleanup projects involving the application of cutting-edge remediation technologies. We litigate and win significant cases, and we have unparalleled experience handling high-profile environmental cases. Our team includes some of the most distinguished environmental lawyers in the country. Indeed, two of our partners were recently named Energy & Environmental Trailblazers by The National Law Journal, which recognizes lawyers who “continue to make their mark in various aspects of legal work in the areas of energy and environmental law.”

Our firm’s recognition in the field is extensive. Mayer Brown was honored to be named a Law360Environmental Practice Group of the Year” for four of the past five years. We are continuously recognized by Chambers USA and Legal 500 USA as a top environmental practice. Chambers USA reports, “The team is very strong and responsive advisers. They produce top-notch quality work.” Legal 500 quoted clients who said, “‘Mayer Brown’s service is extremely good,’ [they have] ‘both depth and breadth’ and ‘a consistent track record of providing high quality representation.’”

We have extensive experience in the following areas of Environmental law:  

  • Environmental Litigation and Enforcement
  • Environmental Compliance, Permitting and Counseling
  • Clean Air Act
  • Clean Water Act
  • Environmental Due Diligence in Transactions
Responding to Mass Environmental Tort Litigation: A How-To
Environmental Group of the Year


Litigation & Enforcement

  • We secured a unanimous victory for Weyerhaeuser Company in the US Supreme Court by obtaining reversal of a Fifth Circuit decision holding that the US Fish and Wildlife Service properly designated private land in Louisiana as “critical habitat” for the endangered Dusky Gopher Frog under the Endangered Species Act, even though there are no frogs on the land and radical changes would have to be made in the land before the frog could live there. The Court held that “critical habitat” must first be “habitat” for the endangered species and that the agency’s decision whether to exclude property from a critical habitat designation is reviewable in court for abuse of discretion. The Court remanded the case to the Fifth Circuit so that the lower court could apply the correct legal standards in the first instance.
  • We serve as national counsel to an American multinational corporation, in connection with hundreds of claims pending nationwide alleging personal injury, property damage and environmental harm associates with per and polyfluorinated alkyl (PFAS) substances. The claims include actions by various state attorneys general, the Aqueous Film-Forming Foam Multidistrict Litigation pending before the Honorable Richard Gergel, and numerous additional claims.
  • We successfully defended Nicor, a major natural gas supplier, against claims by the City of Evanston, Illinois, alleging that contamination caused by Nicor migrated a half-mile into the city and contaminated its water mains, putting the health of the city’s 77,000 residents at risk. The city demanded an injunction that would require Nicor to conduct a detailed study and to prepare to replace miles of aging city water mains at a cost of hundreds of millions of dollars. After a two-week trial that included more than 10 experts, a federal trial court ruled in favor of Nicor, determining that there was no evidence that the water mains were contaminated by Nicor and no evidence that the city’s water posed a risk to its residents.
  • We successfully represented 14 major industry groups in challenging the legality of the United States Environmental Protection Agency’s 2015 regulation defining “the waters of the United States” within the meaning of the Clean Water Act (CWA). We served as lead counsel and obtained certiorari over United States’ opposition, and prevailed 9-0 on the merits on issue of where challenges to EPA’s “Waters of the U.S.” rule may be litigated. The case was featured in Law360’s “Biggest Environmental Rulings of 2018.” Subsequently, on remand, we persuaded the district court that the 2015 Rule violates the Administrative Procedure Act.
  • We represent Veolia, a French transnational company, and its US subsidiary in connection with the Flint Water Crisis—one of the highest-profile cases in the United States. Veolia was hired by the city to assist with issues—other than lead—associated with the water supply. Even though governmental investigations into the cause of the crisis have identified governmental actors—not Veolia—as the source of the problem, plaintiffs have targeted Veolia. We represent Veolia against these unwarranted allegations of wrongdoing amidst a volatile political environment and successfully defended the company through a 6-month trial in federal court that resulted in a mistrial.
  • We represent Cargill with respect to a CERCLA site in Grand Island, Nebraska involving soil and groundwater contaminated with chlorinated solvents. U.S. EPA listed the site on the National Priorities List under CERCLA and initiated remedial action. Working with a team of experts, we commented on the proposed remedial action and defended the company against claims by approximately 300 residents who alleged extensive personal injuries and property damages. Plaintiffs alleged that the majority of the solvents originated from a former Cargill facility. Plaintiffs’ counsel used Erin Brockovich extensively to recruit clients and obtain favorable local publicity. After extensive expert work, including additional investigation in the field and carefully targeted fact discovery, we prevailed on summary judgment on grounds that Cargill did not cause the contamination and did not have a duty to investigate the property to discover subterranean contamination. Avila v. CNH America LLC, 2009 WL 151600 (D. Neb. 2009), reconsideration denied, 2009 WL 666386 (D. Neb. 2009). In addition, we used the summary judgment to establish that there was insufficient evidence for EPA to identify Cargill as a PRP for the site.
  • For a decade, we have been lead counsel in multi-party litigation over sediment contamination in the Penobscot River in Maine. City of Bangor v. Citizens Communications Company, et al., No. 02-cv-00183 (US Dist. Ct. Maine, filed 2002). The litigation was initiated by the City of Bangor against our client, Frontier Communications Corp., f/k/a Citizens Utilities Co. The City sought to hold Frontier solely responsible for cleanup costs of over $100 million and for punitive damages of over $50 million due to polycyclic aromatic hydrocarbon (PAH) contamination allegedly discharged from a manufactured gas plant that began operations in 1851. The dispute presented complex issues of causation and involved a score of third and fourth-party defendants who had operated along the waterfront. Following extensive discovery and a three-week trial, we negotiated a settlement that allowed Frontier to limit its cleanup costs to $7.625 million, while requiring the City to conduct all cleanup and to indemnify Frontier without limitation. The settlement, embodied in a consent decree with the State of Maine, also allowed Frontier to recoup its costs from third parties, who challenged the arrangement as unreasonably favorable to Frontier. The US Court of Appeals for the First Circuit unanimously approved the settlement. City of Bangor v. Citizens Communications Co., 532 F.3d 70 (1st Cir. 2008). Frontier subsequently has recovered almost all of its cleanup costs through third-party settlements, and the litigation is substantially complete.
  • We represent a major gas distribution company in the process of investigating and remediating its historic manufactured gas plant (MGP) sites and defending the significant litigation that has arisen at a number of sites. Thousands of MGPs were built nationwide in the late 19th and early 20th centuries to supply manufactured gas – made from liquefying coal - to nearby communities to use for light and heat. These facilities became outmoded by approximately 1945 with the advent of relatively inexpensive natural gas supplied via interstate pipelines. When the facilities were closed, the liquid tar byproduct (“coal tar”) and other chemicals were often left behind, typically in underground storage facilities. MGPs often involve remedial costs exceeding $50 million; in some cases, over $200 million, and include difficult issues involving rivers and river sediments, fractured bedrock, and related air emissions and risk assessments. We have represented the company in associated litigation, including more than a dozen cases involving statutory claims under CERCLA and RCRA as well as class action and individual tort claims by neighboring residents alleging personal injuries and property damages caused by exposure to MGP contaminants. In litigation, we have achieved victories via motion practice to position the cases for favorable settlement, while also resolving favorably various investigations initiated by government agencies.
  • Using its authority under CERCLA Section 104(e), the US EPA sought to enter private property to conduct a CERCLA removal action. On behalf of the property owner, we brought an action challenging the 104(e) order. At trial, our team defeated EPA and the US Department of Justice. The win was affirmed on appeal to the 7th Circuit. The victory achieved was so decisive that the trial court subsequently required the US government to pay Mayer Brown’s attorneys’ fees under the Equal Access to Justice Act. This case is the first recorded instance of EPA losing a demand for access under CERCLA Section 104(e). U.S. v. Tarkowski, 248 F.3d 596 (7th Cir. 2001); U.S. v. Tarkowski, 2002 WL 460831 (N.D. Ill. 2002).
  • In Comer v. Murphy Oil Co., plaintiffs – Mississippi property owners harmed by Hurricane Katrina – sued oil, coal power, and chemical companies for public nuisance, alleging that the defendants’ emissions of greenhouse gases caused the oceans to warm, which caused Hurricane Katrina to be stronger than otherwise would have been the case, which increased the damage the hurricane caused to plaintiffs’ properties. The District Court dismissed the suit on grounds that it presented a non-justiciable political question and that plaintiffs lacked standing to pursue the claims, but a Fifth Circuit panel reversed. After we persuaded the Fifth Circuit to rehear the case en banc, the en banc Court lost its quorum to decide the case due to a recusal, leaving the favorable District Court decision controlling. Plaintiffs then filed a petition for mandamus in the US Supreme Court seeking to reinstate the panel decision instead. We persuaded the Supreme Court to deny mandamus, leaving the District Court decision dismissing the suit as the controlling law of the case. After the plaintiffs refiled their claims, we obtained dismissal of their suit on res judicata and other grounds.
  • We represent Dow Agrosciences in Holiday Shores Sanitary District v. DowAgrosSciences, LLC, a class action pending in Madison County, Illinois, in which the plaintiffs allege that a common herbicide, atrazine, has contaminated dozens of community water supplies. This litigation involves cutting-edge science regarding toxicity endocrine disruption, and also involves complex expert investigation regarding the fate and transport of alleged contaminants as they relate to both product identification and alleged causation. Issues related to atrazine, and the US EPA’s decision to conduct multiple scientific advisory panel hearings regarding the compound, have been covered by the New York Times, Wall Street Journal and other national media outlets.
  • We have filed a certiorari petition in Tarrant Regional Water District v. Hermann, No. 11-889 (US), on behalf of the Texas water district serving Fort Worth. The petition asks the Court to review a Tenth Circuit ruling that upheld Oklahoma laws that improperly burden interstate water transfers and prevent Tarrant obtaining water from Oklahoma that it is entitled to under the terms of the Red River Compact. Tarrant contends that these Oklahoma laws violate the dormant Commerce Clause and are preempted by the congressionally enacted Compact. In response to our petition, the Supreme Court has asked the United States to file a brief stating its views.
  • We represented BNSF in a number of cases stemming from historic railroad operations. The complaints allege that BNSF contaminated the soil and groundwater in Livingston, damaged the plaintiffs’ properties, and that the plaintiffs are entitled to monetary awards to fund further “restoration” above and beyond the cleanup that BNSF is already implementing subject to oversight from the Montana Department of Environmental Quality. There are over 100 plaintiffs involved in the various suits filed in both state and federal court.

Regulatory Challenges, Compliance, Permitting and Counseling

  • We have been advising an aluminum manufacturer about hazardous waste permitting and RCRA corrective action obligations.  In connection with an acquisition, our client took over a moribund cleanup process at a plant in Decatur, Alabama.  With our help, our client investigated the site, obtained a new hazardous waste permit and developed corrective action plans.  Remediation is now ongoing. Contaminants of concern include chlorinated solvent, petroleum and hexavalent chromium.  In addition, we have been representing our client in its efforts to obtain indemnification for the associated costs pursuant to its business transaction.
  • We represented Arkema in a case that challenged a US EPA regulation allocating allowances for the production and consumption of HCFCs (which are commonly used as refrigerants). Agreeing with Arkema that the allocation rule was inconsistent with EPA’s past approvals of allowance transfers, and was unlawfully retroactive, the DC Circuit issued an opinion vacating the rule “insofar as it operates retroactively” and remanding the case “for prompt resolution.” The government was unsuccessful in obtaining rehearing, and we represented Arkema on issues relating to the vacatur.
  • We represent a metal supplier in connection with its status as a Potentially Responsible Party at the Portland Harbor Superfund Site, one of the largest and most complex Superfund sites in the country. The site consists of a 10-mile stretch of the Willamette River in Portland, Oregon. Contamination at the site is connected to industrial operations dating back over 100 years. EPA has identified over 150 Potentially Responsible Parties, including both private, state, and federal entities. EPA recently released its proposed cleanup plan for the site, which it anticipates will cost approximately $750 million dollars.
  • Representing forest and paper products companies and trade groups and Tillamook County, Oregon, we successfully petitioned (over the contrary recommendation of the United States) for Supreme Court review of a Ninth Circuit decision holding that channeled discharges of stormwater from logging roads require National Pollutant Discharge Elimination System (NPDES) permits pursuant to the Clean Water Act. By a vote of 7-1 the Supreme Court reversed the court of appeals’ adverse ruling, holding that U.S. EPA had the authority to determine that forest road runoff is not “industrial” in nature and therefore does not require an NPDES permit. Even before the Supreme Court acted on the merits of the case, EPA handed our clients a victory by promulgating a new regulation that clarified its long-held position that forest road discharges do not require permits and are more effectively regulated by the States using best management practices. The Court accepted our argument, however, that this regulatory change did not moot the issues on which certiorari had been granted. The case is Decker v. Northwest Environmental Defense Center, Nos. 11-338 & 11-347 (U.S. Sup. Ct. Mar. 20, 2013).
  • We represented Arkema in Arkema Inc. v. EPA, 618 F.3d 1 (D.C. Cir. 2010). In that case, Arkema challenged a 2009 U.S. EPA regulation allocating allowances for the production and consumption of HCFCs (which are commonly used as refrigerants). Agreeing with Arkema that the allocation rule was inconsistent with EPA’s past approvals of allowance transfers, and was unlawfully retroactive, the D.C. Circuit issued an opinion vacating the rule “insofar as it operates retroactively” and remanding the case “for prompt resolution.” The government was unsuccessful in obtaining rehearing, and we now are representing Arkema on issues relating to the vacatur.
  • We represent United States Sugar Corporation in two cases concerning whether Clean Water Act permits are required for water transfers, e.g., pumps and dams, that move navigable water. The entire U.S. water supply system depends on thousands of water transfers, the vast majority of which do not currently require permits under the Clean Water Act. The cost of permitting, and opportunities for litigation that the permit system would introduce, would have enormous adverse effect on public water managers and water users. U.S. Sugar intervened as a defendant in Friends of the Everglades v. South Florida Water Management District, where environmental groups sued the District to require permits for its water transfers. After the Southern District of Florida rendered an adverse decision, we successfully appealed to the Eleventh Circuit. The Supreme Court denied the environmental groups’ petition for certiorari, leaving the successful Eleventh Circuit decision intact. Friends of the Everglades v. South Florida Water Management District, 2006 WL 3635465 (S.D. Fla. 2006), rev’d in part, appeal dismissed in part by 570 F.3d 1210 (11th Cir. 2009), reh’g en banc denied by 605 F.3d 962 (11th Cir. 2010), cert. denied, 131 S. Ct. 643 (2010).
  • In the second, closely-related matter, Friends of the Everglades v. EPA, a number of environmental groups have challenged EPA’s water transfer rule in the Eleventh Circuit. U.S. Sugar has intervened to oppose those challenges. The case is currently pending in the Eleventh Circuit. Both cases follow from the Supreme Court’s ruling in Miccosukee Tribe v. South Florida Water Management District, 541 U.S. 95 (2004), in which, representing the District, we persuaded the Supreme Court to vacate an adverse Eleventh Circuit ruling that water transfers require NPDES permits.
  • We represent United States Sugar Corporation in two challenges to regulations issued by the U.S. EPA setting emissions limits under the Clean Air Act for hazardous air pollutants from industrial, commercial, and institutional boilers and process heaters (the “Boiler MACT”). These challenges are a continuation of our representation of U.S. Sugar in the rulemaking process, where we provided extensive comments on the proposed rules. In an unusual step, U.S. EPA specifically invited reconsideration at the time it issued the final regulations, and our first challenge is a petition for agency reconsideration on numerous aspects of the regulations, which is pending. Our second challenge is a petition for review of the regulations pending before the D.C. Circuit Court of Appeals.
  • We are presently involved in conducting an investigation into dioxin and pesticide contamination at the U.S. Naval Base at Pearl Harbor, Hawaii. Our client had an interest in agricultural operations conducted on Waipio Peninsula back into the late 1800s, before the Naval Base was established at Pearl Harbor. Sediments in Pearl Harbor are heavily contaminated. EPA and the Navy have asserted that our client is responsible for dioxin, pesticide, PAH, and metals contamination alleged to have been discharged from a pentachlorophenol (PCP) pesticide mixing operation conducted on the Peninsula pursuant to a lease from the Navy following World War II. The client is investigating the site pursuant to a Unilateral Administrative Order issued by EPA. At issue are numerous Navy operations conducted at Pearl Harbor during and following World War II, including use of the defoliants 2,4,5-T and 2,4-D.
  • We represented a consortium of Chicago-area cities and villages that sought to develop landfill for baled nonhazardous solid waste on a 533-acre parcel in Illinois. The parcel had been used for sand and gravel mining until about 1960. Since then, the excavation trenches from the mining had evolved into ponds ranging in size from a few feet across to several acres. The U.S. Army Corps of Engineers asserted that the ponds were “navigable waters of the U.S.” because of their use by migratory birds and denied the permit application. The Supreme Court held that Corps’ rule extending definition of “navigable waters” under the Clean Water Act to include intrastate waters used as habitat by migratory birds exceeded the authority granted to the Corps under the Act. Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001).
  • We are providing regulatory advice to a leading manufacturer of engineered materials and components for building products with respect to waste remediation obligations and its ability to recover the costs through contractual indemnification.
  • We are assisting a diversified chemicals manufacturer to develop legislative and regulatory strategies relating to federal emissions programs.

Environmental Due Diligence in Transactions

  • We represented Caterpillar in conducting environmental due diligence with respect to its acquisition of Bucyrus, a manufacturer of mining equipment which owns or operates over 150 separate facilities worldwide. This was a deal which overall is valued at $7.6 billion and for which the due diligence had to be conducted, worldwide, on an extremely expedited basis.
  • We represented Nestle in its $11.9 billion acquisition of Pfizer’s infant nutrition business, in one of the largest acquisitions of 2012. As part of the representation, Mayer Brown advised Nestle in environmental due diligence and negotiation with respect to manufacturing facilities located in The People’s Republic of China, The Republic of Ireland, The United Mexican States, The Republic of the Philippines and The Republic of Singapore. We continue to represent them in a series of large transactions as part of its efforts to focus on healthier products and provide due diligence support concerning the environmental aspects of these transactions.
  • We represented an international agribusiness client on a number of acquisitions involving the flower and seed businesses. Environmental aspects involved due diligence to establish prospective purchaser and other liability protections, including the retention of environmental consultants, review of Phase I and site visit reports, quantification of potential environmental liabilities, and negotiation of scope of work for Phase II sampling and access agreements; advice on the transferability of permits; and negotiation of deal terms allocating responsibility for known and unknown environmental conditions and mechanisms for post-closing environmental risk management, such as cost‑sharing agreements and escrows.
  • We represent United States Steel Corporation with respect to the redevelopment of its former 537-acre steel manufacturing operations at the Chicago South Works Site. We have assisted United States Steel Corporation in obtaining three No Further Remediation Letters and in obtaining a key environmental insurance policy to facilitate the redevelopment of the site. The project is ongoing, and we continue to work closely with US Steel and the redevelopment group. This site represents the largest brownfield site in the City of Chicago, and its redevelopment will turn the currently shuttered facility into a new and productive neighborhood along the shore of Lake Michigan on Chicago’s Southside.
  • We represent a leading North American metal distributor and processor in its acquisition and merger of a steel company, including the identification and management of environmental liabilities. The transaction included the creation of an extensive process to address environmental liabilities post-closing for seven manufacturing facilities. We also represent the client with respect to post-acquisition investigation and remediation of other metal manufacturing and processing facilities.
  • We represented a venture capital fund in connection with the sale of a company, which included environmental due diligence that identified chlorinated solvent contamination at the operating property caused by an historic property owner. On behalf of the client, we brought suit against the historic owner under CERCLA and state law, winning summary judgment on all major issues followed by a favorable overall settlement that included the historic owner accepting responsibility for the site cleanup and the award of attorneys’ fees. We also represented the client in connection with its contractual obligations to the property purchaser, including enrolling the site in the state voluntary cleanup program and providing for ongoing financial assurance.

Representative Clients

  • 3M
  • Arkema, Inc.
  • BNSF
  • Cargill
  • Caterpillar
  • Dow Chemical Company
  • Nicor
  • Ryerson
  • Solvay
  • United States Steel Corporation
  • United States Sugar Corporation
  • Veolia


Law360 recognized Mayer Brown’s Environmental practice as one of its Environmental Practice Groups of the Year for four of the past five years (2022, 2021, 2019 and 2018).

The Legal 500: United States
We have been recognized as a leading Environmental litigation practice since 2008.

Chambers USA
We have been recognized as a leading Environmental practice in Illinois since 2008. 

The National Law Journal
Two partners named Energy & Environmental Trailblazers by The National Law Journal, which recognizes lawyers who “continue to make their mark in various aspects of legal work in the areas of energy and environmental law.”