Chevron Corp. will pay a nearly $3 million fine and spend $160 million on environmental improvements and upgrades at oil refineries in four states to resolve allegations that the company violated pollution laws.

The U.S. Department of Justice said that the agreement ends investigations in four states where Chevron’s refineries caught fire or released harmful chemicals. The settlement calls for it to spend $10 million on environmental projects in California, Mississippi, Utah and Hawaii.

The company also agreed to spend $150 million upgrading refineries throughout the country.

Chevron agreed to replace vulnerable pipes, institute operating parameters and alarms for safer operation, improve corrosion inspections and training, centralize safety authority within the corporation, conduct a pilot study of safety controls for fired heaters and make other safety improvements at all of its domestic refineries.

The Environmental Protection Agency’s (EPA) initial investigation was spurred by an August 2012 fire involving high-temperature hydrocarbons released in the Crude Unit at Chevron’s Richmond, California, refinery. That fire prompted a shelter-in-place order by local officials, endangered 19 employees and caused 15,000 local residents to seek medical attention. During the EPA’s investigation, Chevron experienced accidental releases of regulated chemicals at two of its other refineries, including a 2013 explosion and fire in Pascagoula, Mississippi, that caused the death of an employee, and a 2013 rupture in El Segundo, California, that caused a loss of power and flaring at the refinery.

The Justice Department says the $2.95 million fine will resolve several regulatory investigations, including a 2013 explosion and fire in Mississippi that killed a Chevron worker and a 2012 fire in California that forced the evacuation of 14,000 residents.

According to the Associated Press, Chevron in 2013 paid $2 million in fines and restitution and pleaded no contest to six charges related to the Richmond, California, fire, the AP said. It also agreed to spend $20 million on improving the facility in order to settle claims made by state regulators.

The proposed consent decree was lodged today in the U.S. District Court for the Northern District of California and is subject to a 30-day public comment period and final court approval.