SAN JOSE (CBS SF) – Chevron will spend more than $150 million on safety upgrades throughout its domestic production network as part of a settlement reached with the U.S. Environmental Protection Agency, EPA officials announced Tuesday.

The settlement was reached after an investigation that was prompted initially by a 2012 chemical release at Chevron’s refinery in Richmond.

An estimated 15,000 people sought medical attention after a fire at the refinery released high-temperature hydrocarbons on Aug. 6, 2012, according to the EPA.

County officials issued a shelter-in-place warning due to environmental conditions, and 19 employees were endangered as a result of the fire and chemical release.

During the subsequent investigation, two accidental releases of regulated chemicals occurred at other Chevron facilities, including one involving an explosion that killed worker Tonya Graddy in Pascagoula, Mississippi, in 2012.

“This case demonstrates the importance of performing equipment inspections and maintenance in accordance with environmental regulations,” Susan Bodine, assistant administrator at EPA’s Office of Enforcement and Compliance Assurance, said today in a statement. “Under this settlement Chevron, USA Inc. will improve their safety systems and monitoring equipment, protecting their employees and the surrounding communities.”

In addition to safety and equipment upgrades, Chevron is also required to pay a civil penalty of $2.95 million and put at least $10 million into environmental projects in four states – including California.

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