Daniel J. O'Hanlon

Mr. O’Hanlon focuses on environmental law and includes litigation, counseling and permitting in the areas of water resources, remediation of contaminated property, endangered species, and wetlands. He serves as special counsel to a number of public agencies and associations in the water resources area, including the San Luis & Delta-Mendota Water Authority, Westlands Water District, and the State Water Contractors, as well as represents both public and private entities.

Legal Experience

In practice since 1985, Mr. O'Hanlon is an accomplished litigator with in-depth experience representing clients in a variety of environmental matters including:

  • Water rights matters before the State Water Resources Control Board and state courts involving endangered species, instream flows, and the public trust doctrine
  • Litigation involving the application of the Endangered Species Act, Clean Water Act, National Environmental Policy Act and underlying regulations to the operations of major water projects
  • Obtaining permits under federal and state endangered species laws
  • Advice and counsel regarding rights and responsibilities for remediation of contaminated soil and groundwater
  • Suits under CERCLA, RCRA and state law counterparts, as well as contract and fraud disputes arising out of environmental contamination of real property
  • Toxic torts litigation

Mr. O'Hanlon's litigation experience encompasses a wide range of proceedings, including bench and jury trials, writ of mandate and other administrative record based litigation, appellate practice, arbitration, and mediation.

Prior to joining the firm in 2000, Mr. O'Hanlon was a Partner with Beveridge & Diamond LLP in San Francisco, where he focused on environmental litigation as well as counseling and permitting in the areas of endangered species, wetlands and water resources.

Practice Examples

Recent examples of legal matters Mr. O'Hanlon has handled include:

  • Suits involving challenges to State Water Resources Control Board decisions involving the Bay-Delta, including challenges to Decision 1641 and Standard Permit Term 91.
  • Litigation under NEPA and the ESA regarding changes to the operations of the Central Valley Project and State Water Project.
  • Representation of water districts in litigation involving drainage impaired agricultural land.
  • Representation of a municipality in CERCLA litigation involving allegations of releases from municipal sewers.
  • Representation of local redevelopment authorities with respect to remediation and cost recovery for infill development projects.

Professional Activities & Affiliations

Mr. O’Hanlon’s professional activities and affiliations include:

  • Northern California Super Lawyer (2011, 2012, 2013, 2014, 2015, 2016)
  • Martindale-Hubbell AV Rated Attorney
  • Top Lawyer, Sacramento Magazine, 2016
  • Best of the Bar, Sacramento Business Journal, 2015
  • Member, various committees and subcommittees of the Association of California Water Agencies (ACWA)
  • Member, California State Bar Association
  • Member, American Bar Association
  • Member, Sacramento County Bar Association
  • Editorial Board, California Water Law & Policy 


  • Author, “Sacramento Superior Court Issues Ruling in the Delta Stewardship Council Cases,” California Real Property Law Reporter, July 2016
  • Author, "U.S. Bureau of Reclamation Issues a 'Finding of No Significant Impact' for the Delivery and Use of Unreleased San Joaquin River Restoration Flows," California Water Law Policy Reporter, May 2016
  • Author, "Bill to Implement Westlands Water District Drainage Settlement Introduction in Congress," California Water Law Policy Reporter, March 2016

Academic Background

J.D. University of California, Hastings College of the Law, 1985

B.S. University of California, Davis, 1981