Gas prices have risen 20 cents over the last week, giving California, including Santa Clarita, the most expensive prices in the nation due to planned and unplanned maintenance on refineries, officials said Tuesday.

California’s averages reaching $4 a gallon is the highest motorists have seen gas prices in the state since July of 2014, according to officials.

Gas prices started to rise after a fire burned at the Philip 66 Refinery in Carson on March 15, and that started a series of refinery problems, said Marie Montgomery, a spokesperson for the Automobile Club of Southern California.

Once the fire was extinguished, four out of the 10 refineries in Southern California went under planned and unplanned maintenance, resulting in less gasoline being made.

A majority of the gasoline that is sold in California is made from the local refineries due to California requiring a specific blend of gas to help prevent pollution, Montgomery said.

“The only other state that has the same blend we do is Washington state, and there is no pipe to transport gas down to us,” she said.

If the demand becomes too high, California has to import gasoline by ship from either Washington or overseas, Montgomery said.

The maintenance of the refineries is set to be completed by the second half of May, and relief at the pump is expected.

Another factor of the high gas prices seen in California is the passage of Senate Bill 1, the “gas tax.”

SB1 was signed into law on April 28, 2017, promising to fund road maintenance and reconstruction projects through an estimated $5.2 billion generated from increased gas taxes and vehicle fees.

The legislation raised the state gas tax by 12 cents per gallon and raised the diesel fuel tax by 20 cents per gallon. The measure also created a new annual vehicle fee ranging from $25 for cars valued at less than $5,000 to $175 for cars worth $60,000 or more.

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