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RICHMOND, Calif. (AP) -- Chevron Corp. and state regulators have reached a settlement related to a 2012 fire at its Richmond refinery that will require the company to spend about $20 million on safety upgrades.

Cal/OSHA, the state's workplace safety agency, said in a statement Monday the agreement requires Chevron to replace all carbon steel piping that transports corrosive liquids with chrome-alloy piping, which is better at resisting corrosion.

It says Chevron also has to implement procedures to monitor equipment that alerts operators when replacements are needed.

In 2013, the state fined Chevron nearly $1 million after a fire at their Richmond refinery sent a cloud of gas and black smoke over residential areas.

Investigators found "willful violations" in Chevron Corp.'s response before, during and after the Aug. 6, 2012 fire caused by an old, leaky pipe in one of the facility's crude units.