On Thursday, the California Independent System Operator Corporation (ISO) issued a transmission emergency after a major system disturbance occurred between Arizona and Southern California and caused all of San Diego Gas and Electric (SDG&E) and a small portion of Southern California Edison customers to lose power. 

The outage was triggered after a 500 kilovolt (kV) high-voltage line from Arizona to California tripped out of service. The transmission outage cut the flow of imported power into the most southern portion of California resulting in wide-spread outages in the region. 

Due to the power outage, many public water systems lost pressure in the water distribution system. As a precaution, Boil Water Orders were being issued until laboratory results show the water is free from bacterial contamination. The Boil Water Orders remained in effect until Sunday, when the distribution systems were disinfected and samples confirm the absence of bacteria in the water supply.

However, not everyone was subject to the Boil Water Orders. Helix Water District was able to declare victory after their emergency generators were able to maintain the integrity of their water delivery system throughout the black out.

Helix Water District reports its water system is back to pre-power-outage conditions and customers may return to their normal water-conserving behavior.

“The response by the District was immediate and effective to ensure no customers lost water service during the incident,” Mark Weston, Helix general manager, said.  “We want to thank our customers for responding to our request to curtail their water use to only essential needs during the power outage.”

The district deployed 15 emergency power generators to keep its treatment plant, pump stations and operations center operational throughout the blackout.

Not everyone was able to maintain their systems throughout the power outage.

An estimated 3.2 million gallons of sewage escaped from the San Diego Metropolitan Wastewater System, spilling into the Los Penasquitos Lagoon at the Torrey Pines State Beach. City of San Diego crews worked to control the release, but beaches were still closed with signs posted at major beach access points.

An additional sewage spill occurred at another pump station, resulting in a release of an estimated 120,000 gallons.  This spill flowed into the San Diego Bay.

The California Independent System Operator Corporation (ISO) initiated a joint task force today to investigate the widespread blackout that left more than a million Southern Californians without power for nearly 12 hours. 

“We now turn our focus to root-cause analysis to investigate the reason for the series of events that triggered the widespread power outage,” said ISO President and CEO Steve Berberich.

The Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Corporation (NERC) also announced a joint inquiry in cooperation with the ISO, WECC, all utilities impacted and state regulators in California and Arizona.  WECC has also announced its own Event Analysis that will be conducted with participation from the California ISO.