Chevron U.S.A. Inc. has paid $422,500 in penalties for supplying gasoline and diesel fuel in violation of California regulations designed to protect air quality.

Chevron agreed to pay the penalties as part of three separate settlements it reached with the California Air Resources Board. In all, 15.9 million gallons of fuel were in violation of state regulations, according to a CARB announcement.

In two cases, Chevron disclosed the violations. In the third, CARB enforcement staff discovered the violation as a result of routine fuel sampling.

• Chevron paid $205,000 for supplying more than 385,000 gallons of gasoline in violation of California reformulated gasoline regulations between mid-June 2009 and Aug. 1, 2009.  Dispensed from Chevron terminals in Sacramento and San Jose, the fuel did not contain adequate amounts of ethanol.

• Chevron paid $192,500 for supplying more than 15.5 million gallons of gasoline in violation of California reformulated gasoline regulations. Analysis of gasoline samples indicated olefin levels exceeded certain required specifications. Higher levels of olefin mean more smog will be formed from tailpipe emissions since hydrocarbons, including olefin, react with sunlight and other pollutants to form smog. Chevron was notified by CARB of the violation, and took immediate steps to find and rectify the cause to prevent future occurrences.

• Chevron paid $25,000 in penalties for supplying and selling more than 36,000 gallons of diesel fuel in August 2009 that did not meet a required minimum cetane number. (The cetane number indicates the combustion quality of a diesel fuel, and how likely it is to create excess hydrocarbon emissions. When the cetane number is too low, unburned hydrocarbons, which lead to smog, tend to increase.)