William J. Walsh

William J. Walsh

Of Counsel

Washington, DC
Phone: 202.220.1424    Fax: 202.220.1665


"Great insight into federal environmental regulation." -- Chambers USA 2015 

William J. Walsh is of counsel in the Washington office of Pepper Hamilton LLP and the head of that office’s Environment and Energy Practice Group. He is also a member of the firm’s Sustainability, CleanTech and Climate Change Team. Mr. Walsh defends regulatory enforcement actions and personal injury/property damage liability litigation and provides advice pursuant to a variety of environmental statutes. He advocates changes to environmental regulations and policies and provides counsel on a broad range of environmental issues involving innovative scientific, regulatory, legal and policy questions. Mr. Walsh is listed in Chambers USA: America’s Leading Lawyers for Business.

Mr. Walsh assists clients in identifying and mitigating business risks associated with increasingly complex product safety and chemical ingredient regulations developed under the Consumer Product Safety Act, the National Highway Safety Act, the Environmental Protection Agency’s (EPA’s) toxic substance and pesticide statutes, the California Safe Drinking Water and Enforcement Act (commonly referred to as Proposition 65), and the California Safer Consumer Product (SCP) regulations, among other statutes and regulations. This work includes:

  • tracking regulatory developments for clients to provide early warning of significant new regulations or risks to a company's business
  • developing advocacy strategies for responding to regulatory agency and press concerns about the presence of "toxic" chemicals in products
  • commenting in rulemaking proceedings
  • assisting clients in obtaining regulatory approvals pursuant to the pesticide and toxic substance laws, including defending enforcement actions and advising on labeling
  • assisting clients on how to respond to increasing demands to make their companies and products more sustainable
  • advising clients in due diligence investigations on complex future environmental risks that are likely to impact the economics of a transaction, such as vapor intrusion risk, climate change risk, and the risk of new expensive environmental regulations, among other issues.

He has also defended clients involved in complex hazardous substance cleanup sites, negotiating lower remediation costs. More recently, he has defended clients in groundwater-related vapor intrusion remediation and personal injury/property damage cases, particularly in developing scientific challenges to regulatory toxicity factors.

Before joining Pepper in 1986, Mr. Walsh served as the chief of the EPA’s Drinking Water and Wetlands Enforcement Branch and was lead EPA counsel on the precedent-setting hazardous waste lawsuits brought against Occidental Chemical Corporation concerning the Love Canal and related landfills.

Mr. Walsh has written and spoken on a wide range of topics, including regulation and cleanup levels, choosing cleanup goals and technologies, the use of groundwater models in the regulatory system, and the distinction between personal injury claims and regulatory limits. Mr. Walsh has frequently advised the National Academies of Science, including Committees on Groundwater Cleanup Alternatives, Adaptive Site Management at Navy Facilities, Use of Groundwater Modeling in the Regulatory System, and methods of destroying chemical weapons. In each case, he has approached complex scientific and policy issues in a manner that facilitated development of a fair and scientifically sound consensus.


  • J.D., George Washington University National Law Center , 1978, Elected to the Order of the Coif.
  • B.S., Physics, cum laude, Manhattan College, 1968

Bar Admissions

  • District of Columbia

Practice Areas