The California Air Resources Board announced that Chevron Corp. has paid $329,700 in penalties for self-disclosed violations of California’s reformulated gasoline regulations.

Chevron supplied gasoline in violation of state regulations at its Montebello and Richmond terminals. In each case, the self-disclosed violations were for a total of 4.4 million gallons of over-oxygenated fuel that exceeded the standard, a 10% cap by volume for oxygenate. In both cases oxygenate volume of the gasoline was about 11%.

Oxygenates are added to gasoline to help reduce the carbon monoxide and soot that’s created when fuel is burned. The content of oxygen in gasoline must be within a specified range since too much oxygen causes the engine to produce excessive emissions of nitrogen oxide, a key ingredient of smog.

An estimated 3.75 million gallons of fuel exceeding the standard was supplied for 48 days in late 2010 at Chevron’s Montebello terminal and another 660,000 gallons of non-compliant fuel was supplied for four days in April 2011 at the Richmond terminal. In both cases, Chevron blamed an equipment malfunction for causing meters to inaccurately report the volume of premium grade CARBOB, a blendstock that is mixed with oxygenate before being trucked to retail gas stations.

Chevron fully cooperated with ARB in this matter and took steps to correct the violations. Of the $329,700 in penalties, $247,275 will go to the California Air Pollution Control Fund and $82,425 will go to the Statewide School Bus and Diesel Emission Reduction Supplemental Environmental Project (SEP) administered by the San Joaquin Valley Air Pollution Control District. The project is designed to retrofit or replace old, dirty diesel school buses operating in California.