By Laila Kearney

SAN FRANCISCO (Reuters) - The Northern California city of Richmond on Friday sued Chevron Corp, saying the company was willfully negligent in a massive refinery fire and a smoke cloud last year that sent thousands of people to hospitals.

Richmond city officials filed the lawsuit in Contra Costa Superior Court seeking unspecified damages.

Health workers, environmental and community groups planned to rally in Richmond on Saturday in advance of the one-year anniversary of the August 6 fire. The fire, which was started by a pipeline rupture, knocked out the refinery until April.

"The lawsuit seeks damages for the harm caused to the city of Richmond and its community but more importantly is designed to make sure that Chevron changes its corporate culture and makes sure the same thing doesn't happen again," said Frank Pitre, one of the lawyers representing the city in the lawsuit.

The 39-page complaint alleges Chevron "sacrificed safety over profits" and ignored repeated warnings of the risks of pipe corrosions and delayed repairs and inspections.

It also stated that the fire was not unavoidable and followed a dozen similar incidents at Chevron in two decades.

A representative for Chevron did not return a call or email.

In April, the U.S. Chemical Safety Board found fault with California's regulatory system, which it said needed stricter requirements in order to prevent accidents and enforce safety at high-hazard industrial plants such as Chevron's Richmond site.

The blaze sent a fireball skyward and a plume of smoke into the air that lingered above Richmond and neighboring cities for days. At least 15,000 people went to hospitals with respiratory complaints in the hours and days after the fire.

By January, Chevron said it had paid $10 million in claims connected to the blaze, with over 23,300 claims made, according to a letter from Chevron to a local health department.

Pitre said the city waited a year to sue Chevron because it first attempted to negotiate with the company. Richmond City Councilman Tom Butt said the city met with Chevron representatives three times before deciding to sue.

(Editing by Alex Dobuzinskis and Bill Trott)

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