Stephen J. O'Neil is a partner in the firm's Los Angeles office, where he specializes in environmental law and complex environmental litigation.

Areas of Practice

Stephen has extensive experience in environmental counseling and in environmental and toxic tort litigation.  He has advised major oil companies in environmental regulatory matters, and he regularly counsels clients on the environmental implications of the purchase or sale of real property.  He has tried or arbitrated numerous environmental cases, and he has extensive experience in managing large, complex environmental cases and conducting depositions and discovery.  He has conducted settlements with the United States Environmental Protection Agency, and has been engaged in complex Superfund litigation and private cost recovery actions under the Comprehensive Environmental Response, Compensation and Liability Act ("CERCLA"), the Resource Conservation and Recovery Act ("RCRA") and various state and environmental laws.  He has also appeared before numerous state and local environmental agencies.



Representative Litigation Experience

Exide Technologies v. Department of Toxic Substance Control (Los Angeles Superior Court Case No. BS143369)

Mr. O’Neil was co-lead trial counsel in an administrative trial relating to airborne emissions and alleged leakage from stormwater sewers at the Exide Technologies lead battery recycling facility in Vernon, California. Mr. O’Neil obtained a temporary restraining order and a preliminary injunction against the California Department of Toxic Substances Control, which reversed an order that the DTSC had issued that shut down the lead battery recycling facility with no notice. 

Carlton Sullins, an individual, Rita Sullins, an individual, and Don-Sul, Inc., a California Corporation, v. Exxon/Mobil Corporation, a New Jersey Corporation (United States District Court, Northern District Of California Court Case No. 4:08-cv-04927-CW)

Mr. O'Neil represented defendant Exxon Mobil Corporation in a lawsuit brought by an owner of contaminated property in Livermore, California.  Mr. O'Neil tried the case before a jury in Oakland, California in the summer of 2010.  Exxon Mobil obtained a defense verdict.

Carrier Corporation v. Detrex Corporation (Los Angeles Superior Court Case No. C703625).

Mr. O'Neil represented the defendant in a $100 million lawsuit brought by a subsidiary of the United Technologies Corporation.  Plaintiff alleged that Detrex negligently designed and installed a large industrial degreaser, and that the defendant's negligence resulted in the contamination of a groundwater aquifer in the San Gabriel Valley.  Mr. O'Neil tried the case over three months in 1994 and 1996 and won a defense judgment for Detrex.

Lori Lynn Moss, et al. v. Venoco, Inc., et al. (Los Angeles Superior Court Case No. BC 297083).

Mr. O'Neil represents an independent oil company in a toxic tort case brought by Erin Brockovich and Edward Masry of movie fame.  The plaintiffs alleged that exposure to benzene had resulted in a "cancer cluster" among former students of Beverly Hills High School.  Mr. O'Neil's client and the other defendants obtained summary judgment in their favor. 

Bodycote Thermal Processing, Inc., Plaintiff v. Union Bank Of California, as Executor of the Estate Of Joseph Claus Collins, Deceased, et al. (United States District Court Case No. CV-05-6163-R)

Mr. O'Neil represented Union Bank of California, as Executor of the Estate of Joseph Collins.  The plaintiff in this CERCLA action alleged that the Collins Estate had contaminated a property in Inglewood with chlorinated hydrocarbons.  Mr. O'Neil settled the case upon highly favorable terms for Union Bank and the Collins Estate.

Slauson Boyle Venture, a California general partnership, v. USPCI, INC., a Delaware corporation; Chemclear, Inc. of Los Angeles, a Delaware corporation; Chemclear, Inc., a Massachusetts corporation; Clean Harbors, Inc., a Massachusetts corporation, et al. (Los Angeles Superior Court Case No. BC 047822)

Mr. O'Neil represented the owner of a hazardous waste transfer, storage and disposal facility in a breach of contract action against the seller of the facility.  The case involved complicated permitting matters and environmental compliance matters.  Mr. O'Neil settled the case on terms that were highly favorable to his client, Clean Harbors.

Ring Trading Corporation v. The City of Santa Monica – (Los Angeles Superior Court Case No. BC 172044)

Mr. O’Neil represented the owner of a mobile home park in the City of Santa Monica, which the City wanted to close for environmental reasons. Mr. O’Neil negotiated a successful settlement through which his client, Ring Trading Corporation, sold the mobile home park to the City. The lawsuit involved the alleged migration of landfill gas from a nearby City landfill, and the adequacy of environmental protections at the mobile home park site, including the adequacy of sewer connections.

Southern California Gas Company v. Texaco Exploration and Production, Inc., et al. (Ventura County Superior Court No. Civ. 142695).

Mr. O'Neil represented Exxon Corporation in a $20 million lawsuit brought by the Southern California Gas Company relating to the use of a natural gas sweetening product sold by Exxon and other defendants.  Mr. O'Neil assisted in the negotiation of a de minimus settlement on behalf of Exxon, while the other defendants paid in excess of $9 million to settle the case.

Coca Cola Bottling Company of Los Angeles v. Shell Oil Company, Inc., et al. (United States District Court, Central District of California, Case No. 91-5436 WMB (JRx))

Mr. O'Neil represented the Coca Cola Bottling Company of Los Angeles in a private cost recovery action under CERCLA, the Federal Superfund law.  Mr. O'Neil negotiated a favorable settlement on behalf of the Coca Cola Bottling Company of Los Angeles.

Nader Mirzai v. West Village Plaza Partners, et al. (Santa Barbara County Superior Court, Case No. 197953).

Mr. O'Neil defended Atlantic Richfield Company in an action brought by a landowner for damages resulting from the alleged contamination of his property by a former Atlantic Richfield Company property.  Mr. O'Neil mediated the case to a successful conclusion for Atlantic Richfield.

Representative Environmental Counseling Matters

Collins Estate Sale:

Mr. O'Neil represented the Estate of Joseph Collins and Union Bank of California as the Executor of the Estate, in the sale of an environmentally-impaired property.  Mr. O'Neil obtained multiple protections for the Collins Estate and Union Bank, and his work enabled a sale to be consummated on favorable terms for the Estate and Union Bank.

Massachusetts Mutual Life Insurance Matter:

Mr. O'Neil helped Massachusetts Mutual Life Insurance Company sell a property in Orange County known as The Atrium.  The property was environmentally impaired, which Mr. O'Neil helped discover during the due diligence process.  Mr. O'Neil obtained environmental insurance from the seller and other environmental protections that allowed the sale to be consummated.

Applied Magnetics Sale:

Mr. O'Neil helped his clients sell an environmentally -impaired property in Goleta, California.  In the process of doing so, Mr. O'Neil obtained environmental insurance and obtained a Prospective Purchaser Agreement from the California Central Coast Regional Water Quality Control Board.

BKK Corporation

Mr. O'Neil advised a landfill operator of the environmental consequences under federal law associated with its sale of landfill space in Southern California.

Exxon - Texaco Property Exchange

Mr. O'Neil advised Exxon Corporation regarding the environmental implications of a major property exchange between Exxon and Texaco Refinery and Marketing.

MS Partners - Morgan Stanley

Mr. O'Neil advised a real estate partnership regarding the environmental risks associated with purchasing a portfolio of real estate assets owned by Union Bank.

Roscoe Moss Company - San Jose Water Merger

Mr. O'Neil advised a corporation on the environmental implications of its merger with San Jose Water.



Lawyer of the Year, Best Lawyers, 2023

Recognized for Environmental Litigation, Best Lawyers, 2021-2024

Profiled by Los Angeles Business Journal as one of "L.A.'s Leading Environmental Lawyers."




Member, American Bar Association

Member, State Bar of California (Litigation and Environmental Law Sections)

Member, Los Angeles County Bar Association (Litigation and Antitrust Sections)

Member, California Association of Business Trial Lawyers


J.D., University of California, Los Angeles, 1986

B.A., University of Notre Dame, 1983, magna cum laude


  • California
  • Federal District Courts for the Central and Eastern Districts of California
  • Federal District Court for the Northern District of Illinois
  • U.S. Court of Appeal for the Ninth Circuit
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