"The ISO will support whatever actions are needed to ensure that the San Onofre generating units are safe," said Steven Greenlee, a spokesman for the nonprofit. "That's the first thing. Until we know what is going to happen to them, of course, we're planning ahead for contingencies."
The San Onofre plant has been out of commission since Jan. 31, when a tube in one of its units began leaking a small amount of radioactive steam. Southern California Edison officials have found similar wear elsewhere in the plant, according to the Los Angeles Times.
The ISO then looked around the state for units that could generate power in San Onofre's place. The nonprofit chose the AES units because they had recently been retired and could be restarted fairly easily.
AES sold the units last year to Edison Mission Energy, a Southern California Edison affiliate based in Santa Ana, then leased them back and continued to operate them as usual.
Edison Mission is building a new power station, known as Walnut Creek Energy LLC, in the city of Industry and arranged with AES to have the units shut down by the end of this year, Pendergraft said.
However, AES went ahead and shuttered the units in January because it had no customer lined up to buy the electricity they generated. To restart the units, crews will have to make several repairs, including removing blanks from gas lines, fixing electrical connections and filling holes in boiler walls.
If the ISO does end up needing the units, they will likely operate for a short time, Pendergraft said.
"I would anticipate it's just for the summer and until the San Onofre units become operational again," he said. "But even if San Onofre is not operational come November, we would still be required to shut units 3 and 4 down to allow Walnut Creek to go into operation."
Pendergraft added that his company was still dealing with regulatory issues and expected to start repair work early next week.
The amount of power generated by the AES units will not be enough to replace the amount San Onofre would produce, Greenlee said.
As a result, the ISO may take other measures to compensate for the energy loss, including upgrading transmission lines and broadcasting announcements to urge residents to limit their power use.