Arizona Public Service won’t be the only utility to pay a price for a major power outage three years ago. A Southern California utility will pay three times as much as APS.

The customer-owned utility serving the Imperial Valley of California will pay $12 million for its part in the blackout, which came amid a heat wave, with heavy power demand in September 2011.

The U-T San Diego reports the Imperial Irrigation District will pay $3 million to the U.S. Treasury and invest $9 million more dollars in reliability enhancements to the local electric grid. 

A settlement with the Federal Energy Regulatory Commission was announced Thursday.

FERC found failures in both the day-ahead and the real-time contingency plans of the Irrigation District. Federal officials also say the district has a prior history of violating reliability standards, including some of the same standards that led to the massive blackout.

APS last month agreed to a $3.25 million penalty for its part in the botched maintenance procedure that touched off the blackout, at a transmission switch yard outside Yuma.