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David G. Mandelbaum represents clients facing problems under the environmental laws. He regularly represents clients in lawsuits and also has helped clients achieve satisfactory outcomes through regulatory negotiation or private transactions. A Fellow of the American College of Environmental Lawyers, David teaches Superfund, and Oil and Gas Law in rotation at the Temple University Beasley School of Law as well as an environmental litigation course at Suffolk (Boston) Law School.

Mr. Mandelbaum has been engaged in matters involving allocation of costs among responsible parties, especially under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), ever since United States v. Atlas Minerals, the first multi-generator Superfund contribution to go to trial in 1993. He has tried large cases and resolved others as lead counsel. He has written, spoken, and taught extensively on the subject. More recently he also has been engaged to assist lead counsel from this firm and others:

  • to develop cost allocation methodologies;
  • to craft expert testimony in support of a favored methodology (given a definition of “fairness,” why one methodology better tracks it than another);
  • to develop efficient case management approaches;
  • to manage portfolio of contaminated properties and related risks and litigation; and
  • to assist private allocation as part of a neutral team.

Mr. Mandelbaum has advised clients on specific compliance and enforcement questions, and broader issues of compliance management systems, sustainability policies, and, more recently, strategies concerning “ESG.”



  • Represent former owner of an Illinois oil refinery in contribution litigation under CERCLA for costs of actions to address groundwater contamination at the facility and in the surrounding area. Premcor Ref. Grp. Inc. v. Apex Oil Co., Inc., No. 3:17-cv-738 (S.D. Ill).
  • Represent party alleged to be responsible for the Lower Passaic River Superfund Site in an allocation proceeding convened by EPA and in private cost recovery and contribution litigation. Occidental Chem. Corp. v. 21st Cent. Fox America, No. 2:18-cv-11273 (D.N.J.).
  • Assist allocation neutral with legal issues important to resolution of private allocation dispute for a site in EPA Region 2.
  • Represent pesticide manufacturer in litigation over selection of RCRA corrective action for arsenic in soils. FMC Corp. v. NYSDEC, 101 N.E.3d 379 (N.Y. 2018), and related federal and administrative litigation.
  • Represent paper manufacturer in enforcement, cost recovery, natural resources damages, and contribution litigation arising from the Lower Fox River and Green Bay Superfund site.  NCR Corp. v. Geo. A. Whiting Paper Co., No. 2:08-cv-16 (E.D. Wis.); United States v. P. H. Glatfelter Co., No. 2:10-cv-910 (E.D. Wis.).
  • Represent industrial parties in connection with the Sheboygan River and Harbor Superfund site, the Lower Passaic River Site, and scores of other Superfund or contaminated sites.
  • Represent underflowed property owner in connection with claim for diminution in value.  Tri-Realty Co. v. Ursinus College, No. 2:11-cv-5885 (E.D. Pa. consent decree entered Sept. 25, 2017).
  • Represented permittee in third-party appeal of greenhouse gas accounting provisions of air pollution permit for natural gas pipeline compressor station engines. Group Against Smog & Pollution v. Department of Environmental Protection, No. 2012-127-R (Pa. EHB settled June 28, 2013).
  • Represented plaintiff oil, gas and mineral estate holder in action for declaration of rights to access its property in the Allegheny National Forest. Seneca Resources Corp. v. United States Forest Service, No. 1:09-cv-154-SJM (W.D. Pa. Mar. 19, 2013).
  • Represented client on the brief for amicus curiae Business Round Table in public nuisance case by state attorneys general against emitters of greenhouse gases. American Electric Power Co., Inc. v. Connecticut, 564 U.S. 410 (2011).

Recognition & Leadership

  • Team Member, a Law360 “Environmental Practice Group of the Year, 2022
  • Honoree, Pennsylvania Bar Association Environmental and Energy Law Section, "Environmental Law Lifetime Achievement Award," 2022
  • Listed, Chambers USA Guide, 2003-2023
  • Listed, Who's Who Legal, 2013-2022
    • Thought Leaders – USA, Environment, 2023
    • Global Leader, Environment, 2013-2022
  • Listed, Euromoney's Expert Guide to the World’s Leading Experts in Environmental Law, 2017-2021
  • Listed, The Legal 500 United States, 2014-2023
    • Environment - Litigation, 2014-2023
      • "Recommended Lawyer," 2022
      • "Other Key Lawyer," 2022 and 2023
    • Environment - Regulatory, 2018-2023
      • "Other Key Lawyer," 2022 and 2023
    • Dispute Resolution - Product Liability, Mass Tort and Class Action - Toxic Tort - Defense, 2018-2019, 2021
  • Listed, The Best Lawyers in America, Environmental Law; Litigation - Environmental; Water Law, 2006-2024
    • "Lawyer of the Year," Litigation - Environmental, Philadelphia, 2016 and 2024
    • "Lawyer of the Year," Environmental Law, Philadelphia, 2015 and 2018
  • Listed, Boston magazine, "Top Lawyers - Land Use Environment," 2022
  • Listed, Super Lawyers magazine, Pennsylvania Super Lawyers, 2004-2023
  • Team Member, The American Lawyer’s “Regional Litigation Department of the Year - Pennsylvania,” Finalist, 2018
  • Team Member, U.S. News - Best Lawyers®, Best Law Firms Edition, "Law Firm of the Year," Environmental Law, 2016
  • Selected, National Law Journal magazine, "Energy & Environmental Trailblazer," 2015
  • Rated, AV Preeminent® 5.0 out of 5.0

°AV®, AV Preeminent®, Martindale-Hubbell DistinguishedSM and Martindale-Hubbell NotableSM are certification marks used under license in accordance with the Martindale-Hubbell® certification procedures, standards and policies.

  • Fellow, The American College of Environmental Lawyers, 2020-Present
  • Course Planner, Pennsylvania Environmental Law Forum
  • Adjunct Professor
    • Suffolk University Law School, Environmental Litigation, Spring Semester 2021
    • Temple University James E. Beasley School of Law, Oil and Gas Law, Environmental Law, Superfund Litigation, Global Climate Change Law, 1990-Present
  • Former Member, Delaware Valley Regional Planning Commission, 2007-2011
    • Vice-Chair 2009-2010
  • Vice-Chair and Former Subcommittee Chair, Pennsylvania Statewide Water Resources Committee
  • Member, American Bar Association, Section on Environment, Energy and Resources
    • Past Chair, Special Committee on Smart Growth and Urban Policy
    • Member, Annual Conference on Environmental Law Planning Committee, 2009
  • Member, Pennsylvania Bar Association
    • Past Chair, Environmental, Mineral, and Natural Resources Law Section
  • Member, Boston Bar Association, Environmental Law Section
  • Member, The Florida Bar Association, Environmental and Land Use Law Section
  • Member, Maryland State Bar Association, Environmental Section
  • Past Chair, Delaware Valley Environmental American Inn of Court


  • J.D., magna cum laude, Harvard Law School, 1983
  • A.B., summa cum laude, Harvard College, 1980
  • Hon. Louis H. Pollak, U.S. District Court for the Eastern District of Pennsylvania
  • Pennsylvania
  • Florida
  • Maryland
  • Massachusetts
  • Supreme Court of the United States
  • U.S. Court of Appeals for the Fourth Circuit
  • U.S. Court of Appeals for the Second Circuit
  • U.S. Court of Appeals for the Seventh Circuit
  • U.S. Court of Appeals for the Third Circuit
  • U.S. District Court for the Eastern District of Pennsylvania
  • U.S. District Court for the District of Columbia
  • U.S. District Court for the District of Massachusetts
  • U.S. District Court for the Eastern District of Wisconsin
  • U.S. District Court for the Middle District of Florida
  • U.S. District Court for the Middle District of Pennsylvania
  • U.S. District Court for the Western District of New York
  • U.S. District Court for the Western District of Pennsylvania