"He is fantastic, has an incredible amount of expertise and a vast skill set."

"Is very knowledgeable and aggressive on behalf of the client while maintaining a calm and collegial demeanor…an expert in his field in environmental matters and always does a great job for us." 

Chambers USA


Mark Ter Molen serves clients on large environmental tort cases involving hundreds, if not thousands, of claimants, as well as other complex environmental and general civil matters. For over 30 years, Mark has counseled and represented clients in complex federal and state trials and appeals, including putative class actions; complex environmental trials and appeals, including governmental enforcement, as well as private party litigation; and environmental regulatory hearings and appeals conducted before state and federal agencies. He also provides general corporate counseling on environmental compliance issues and environmental concerns in the context of corporate transactions, supervises environmental remediations pursuant to various state and/or federal requirements, and conducts condemnation and property valuation actions.

Mark is the co-chair of Mayer Brown's Environmental Litigation group, which has been recognized multiple times as one of the "Environmental Litigation Practice Groups of the Year." He has been listed among The Best Lawyers In America (2017-2024) in the fields of Environmental Law and Environmental Litigation and was named "Lawyer of the Year" in both 2024 and 2021. Mark was also honored with the Illinois State Bar Association's John C. McAndrews Pro Bono Service Award for outstanding pro bono work in the state for his work in reversing the conviction of a man on Illinois' death row and subsequently establishing his actual innocence.

Mark previously served as chair of Mayer Brown's Mass Tort Litigation group.

Clients served by Mark include Cargill, Dow Chemical and Kerry Foods.

Spoken Languages

  • English
Responding to Mass Environmental Tort Litigation: A How-To


  • U.S. Sugar Litigation. Ongoing – Acting as lead counsel for U.S. Sugar Corporation in defending a putative class action alleging that the industry's practice of burning sugar cane fields before harvesting causes personal injury and primary damage.
  • Secured a trial victory for Nicor in a suit brought by the City of Evanston, IL alleging that contamination caused by Nicor migrated 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.
  • City of Evanston v. Nicor Gas Co., et al. Won the dismissal of all claims asserted by the City of Evanston, IL alleging that contaminants from a former manufactured gas plant contaminated the city's water supply. The initial complaint by the city was dismissed after the court determined, among other findings, that methane gas allegedly leaking from operating natural gas pipelines did not qualify as a "solid waste" for purposes of the RCRA.
  • Flint Water Litigation. Represented Veolia Environment in the substantial litigation in state and federal court alleging damages associated with exposures to lead and Legionella bacteria resulting from the Flint, MI water crisis. Completed a six-month jury trial in Ann Arbor, MI federal court, the first of the so-called Flint "bad water" cases, which resulted in a mistrial for Veolia North America.
  • Paulsboro Derailment Litigation. Ongoing – Representing CSX in the significant litigation associated with the derailment of a train, and a related chemical release, in Paulsboro, NJ. On behalf of CSX, defeated class certification for the numerous putative class cases, won summary judgment for all of the several hundred federal court cases and won summary judgment as well for several thousand of the pending state court cases.
  • Nicor Gas Co. v. Wisconsin Central LTD. Represented Nicor in this successful preliminary injunction action in Cook County, IL related to efforts by Nicor to reconnect a major gas line that ran beneath Wisconsin Central railroad tracks in time for the winter heating season.
  • Representing a metal supplier in connection with its status as a Potentially Responsible Party at the Portland Harbor Superfund Site. The EPA has identified over 150 Potentially Responsible Parties, including both private, state and federal entities. The EPA recently released its proposed cleanup plan for the site, which it anticipates will cost approximately $750 million dollars.
  • Wisconsin Central v. Nicor Gas Co. et al. Ongoing – Representing Nicor in this lawsuit seeking damages resulting from a railroad derailment that Wisconsin Central blamed on work by a Nicor pipe installation contractor, Michels, beneath certain Wisconsin Central railroad track.
  • Shakir v. Bergman, et al, and related cases associated with the mass 2012 highway accident in Northwestern Indiana. Represented CSX in these cases alleging damages associated with multiple vehicle collisions, where the collisions were allegedly caused by thick smoke from a roadside fire allegedly caused by CSX. Successfully resolved cases after expert discovery with pending Daubert motions highlighting the impossibility of CSX having caused the fire.
  • Metropolitan Water Reclamation District of Greater Chicago v. Northern Illinois Gas Company, et al. Successfully resolved litigation brought by the Metropolitan Water Reclamation District against Nicor and ComEd/Exelon regarding cleanup of an 18-acre parcel that was formerly the site of a manufactured gas plant.
  • Represented Pactiv Corporation against claims asserted by more than 8,400 neighboring residents who alleged that they were exposed to air emissions containing dioxins and other chemicals. Ultimately settled all claims asserted against Pactiv on extremely favorable terms after we moved for summary judgment under an Alabama statute of repose.
  • Defended Nicor in numerous putative class cases and over 1,200 consolidated individual cases in Cook County, IL state court alleging personal injuries and property damages from exposure to elemental mercury that was included in certain residential and business gas delivery equipment. Also represented the company in parallel investigations and litigation brought by the Illinois EPA and the Illinois Attorney General's office and additional investigations initiated by the U.S. EPA. We convinced the trial court to stay the private litigation pending resolution of the public litigation and ultimately settled the public litigation on favorable terms. The trial court then agreed with our proposal to address the class cases before the individual cases, and we similarly resolved those cases through a favorable settlement formula. Following the class resolution, we litigated the opt-out individual claims and resolved all on favorable terms.
  • Avila, et al, v. CNH, et al, and Schwan, et al, v. Cargill. Won summary judgment on all claims on behalf of Cargill in consolidated litigation brought by approximately 300 plaintiffs (recruited by Erin Brockovich) alleging personal injury and property damage associated with chlorinated solvent groundwater contamination in Nebraska.
  • Blaylock, et al, v. Sigma Aldrich, et al. Won summary judgment/dismissal on all claims on behalf of Chemtura in this food flavorings lawsuit pending in St. Louis, MO.
  • Gray, et al, v. Derderian, et al. Won summary judgment on all claims on behalf of defendant in tragic "Station Fire" litigation arising out of Providence, RI nightclub fire that killed and injured over 400 individuals.
  • Liesse, et al, v. AGA, et al. Won summary judgment on all claims on behalf of Dow Chemical and Union Carbide where 24 Chicago-area hospital workers alleged various personal injuries associated with exposure to ethylene oxide, which was used as a medical sterilant.
  • Hamilton-Warwick v. Volkswagen Group et al. Represented BMW in this lawsuit seeking damages associated with the alleged use of monkeys in testing for the toxicity of diesel vehicle emissions. Won dismissal of claims.
  • Defended a major airline in two class actions alleging personal injuries related to its use of disinfectants on international flights as required by the laws of non-US jurisdictions. Those claims were ultimately dismissed, and we have continued to counsel the airline on disinfectant use issues.
  • U.S. v. Tarkowski. Represented a property owner in a case against U.S. EPA. The U.S. EPA sought to enter private property to conduct a CERCLA removal action using its authority under CERCLA Section 104(e). On behalf of the property owner, we brought an action challenging the 104(e) order. At trial, our team defeated the EPA and the U.S. 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 U.S. government to pay Mayer Brown's attorneys' fees under the Equal Access to Justice Act. This case is the first recorded instance of the EPA losing a demand for access under CERCLA Section 104(e).
  • Zarem v. Inland Steel Inc. Defended Inland Steel Acceptance Corporation and its former CEO in a two-week jury trial in Cook County state court where the plaintiffs alleged fraud and commercial misdealing with respect to Inland's sale to a partnership that included one of the plaintiffs of a hotel complex in Kalamazoo, MI. We won a directed verdict at the close of plaintiffs' evidence on behalf of the former CEO and received a favorable jury verdict on all of the plaintiffs' claims.
  • American Farm Bureau Federation vs. Veneman et al. Represented American Farm Bureau Federation and a class of affected farmers and ranchers in suing the US Department of Agriculture to prevent them from releasing personal identifying information in response to FOIA requests from animal rights groups who were targeting farmers and ranchers for engaging in predator control activities. We defeated the US Department of Agriculture at trial and obtained a preliminary injunction that was subsequently expanded into a permanent injunction.
  • Ford Dealership Litigation. Represented Ford Motor Company in numerous cases related to dealer termination or the non-grant of a dealership. Obtained summary judgment in numerous cases and achieved very favorable settlements in the others.

Governmental Enforcement Actions. Represented manufacturing, chemical and farming clients in governmental enforcement actions arising out of alleged violations of environmental laws and/or permits seeking significant fines and/or closure of the facility. Victories include serving as lead counsel in United States v. Nicor enforcement action seeking significant fines and injunctive relief associated with PCBs in natural gas pipelines. After extensive pre-trial discovery, the government dismissed its case with prejudice; serving as lead counsel in United States v. Tarkowski, resulting in first reported defeat at trial of a USEPA demand to conduct a removal action.

Private Cost Recovery Claims. Represented numerous clients in federal and state courts prosecuting and/or defending suits seeking recovery of cleanup costs, including experience with private CERCLA cost recovery actions, as well as contractual cost recovery claims, including lead counsel in plaintiff action that succeeded in obtaining attorneys' fees and consultant costs.

Governmental Cost Recovery Claims. Represented clients in federal and state courts in suits seeking to recover environmental cleanup costs, including dealing with issues of allocation and appropriate remediation, as well as with natural resource damages claims.

Administrative Actions. Represented clients in numerous environmentally related agency proceedings, including administrative enforcement actions, permit hearings and appeals, and variance requests before the Illinois Pollution Control Board, and permit appeals and administrative enforcement actions before the U.S. EPA

Environmental Disaster Response/Litigation. Represented manufacturing and refining clients responding to industrial "disaster" incidents, such as plant explosions and sudden fires, including developing and implementing strategies for addressing legal, media, employee and insurance issues and handling lawsuits arising from the incidents.

Citizens' Suits. Represented industrial clients in numerous suits brought by citizens' groups seeking substantial fines for alleged violations of environmental laws and permits.

General Environmental Counseling. Counseled a variety of clients on all aspects of environmental law, including wetlands, permitting issues, hazardous waste disposal, climate change and general liability risks.

Death Penalty Litigation. Served as lead counsel in People v. Jimerson, a seven-year effort that succeeded in persuading the Illinois Supreme Court in 1995 to reverse the conviction and death sentence of Verneal Jimerson, who was tried and convicted in 1985. During retrial, succeeded in establishing Jimerson's innocence and winning dismissal of the charges. Illinois Governor Edgar subsequently granted a pardon on the basis of actual innocence.

Civil Rights Litigation. Prosecuted claims for violation of rights and wrongful imprisonment under federal civil rights laws and state counterpart tort claims, including Jimerson v. Capelli, et al., which resulted in a $36 million settlement for malicious prosecution and wrongful imprisonment.

Environmental and Mass Tort Claims. Represented manufacturing and chemical clients in individual claims, "mass" claims and class action toxic cases in federal and state courts, including defending class certification efforts. Experienced with medical claims alleging injuries due to heavy metal exposure, particle inhalation, benzene, PAHs, diacetyl/food flavorings, solvents, dioxin, asbestos, airline disinfectants and inhalation of toxic fumes/gases. Also deals with property damage claims alleging diminution of value due to contamination of soils and/or contamination of groundwater. Representative clients include Cargill, Chemtura, Dow Chemical, Nicor Gas, Pactiv, Ryerson, Kerry Foods and Union Carbide. Currently serving as national counsel for Dow and Union Carbide in ethylene oxide litigation and for Chemtura in food flavorings litigation.


Cornell University, AB, magna cum laude

The University of Chicago Law School, JD


  • Illinois


  • US Court of Appeals for the Seventh Circuit
  • US District Court for the Northern District of Illinois


  • Founding president of Baker Demonstration School, a 400 student pre-K through 8th grade independent school in Wilmette, Illinois, 2003 to date
  • Various church and municipal volunteer positions
  • American Bar Association, Standing Committee on Environmental Law, Section on National Resources
  • Illinois State Bar Association