San Gabriel Island

San Gabriel Island is the city in California where a nuclear power plant melted down during Day 4 in a chain of attacks planned and carried out by Habib Marwan and other terrorists.

Day 4
Secretary of Defense Heller and his daughter, Audrey, were kidnapped and held hostage by terrorists, who flooded the internet with a broadcast of Secretary Heller's "trial" for what they called "crimes against humanity." Although CTU didn't realize it at the time, the internet broadcast was actually a distraction for the terrorists to use the internet to hack through the safeguards and firewalls of 17 U.S. nuclear power plant computer systems.

When Secretary Heller and Audrey were rescued, CTU agents found an empty briefcase with a logo that led them to a defense contractor, McLennan-Forster. Jack spoke with someone from the company who explained that the briefcase contained something called the Dobson Override device, which could override a nuclear power plant in the case of a disaster. This device could also do the opposite - create a meltdown.

After Marwan stole the Dobson Override and initiated a meltdown of the 17 nuclear power plants, Edgar Stiles found a piece of code that allowed him to prevent the meltdowns by breaking the Override on some of the reactors. He successfully shut down all but 6 of the reactors, one of them being the reactor at San Gabriel Island.

Less than 2 hours later, the reactor at the San Gabriel Island plant began to melt down. An engineer called CTU and informed them that radiation would spill into the atmosphere until the core was exhausted.

CTU continued coordinating the evacuation from San Gabriel Island. CTU also continued to search for Marwan and the Dobson Override in order to stop the other 5 plants from going critical.