This six-hour drill called 'Operation Rolling Chaos' started at 8 a.m. Sunday.
Its purpose is to recreate police, fire and military's initial response to a disaster such as a dam break.
The drill was held at Unitek Education, which is a college that provides professional emergency training.
Nearly 500 people participated in the emergency drill, along with military personnel, California Highway Patrol, police and firefighters.
They're fine-tuning their skills on how to respond to a mass casualty or potential disaster and how to quickly identify survivors, people who can walk and separate them from people who need to be immediately hospitalized.
Organizers cite a 2009 study by the Santa Clara Valley Water District that shows a break in the Anderson Dam near Morgan Hill that could happen and that we all need to be prepared.
"We have some things on the books that have to be done. Earthquakes will take a dam away or take a levee away easily. And don't forget, Sacramento's actually built 12 feet below the level of the river. If the levee breaks, Sacramento will be flooded in 12 feet of water," said State Military Reserve Colonel Anthony Dintcho.
Organizers say there was a disconnect between first responders and military officials during Hurricane Katrina that sometimes hindered rescue efforts.
The goal of this simulation was to get different emergency responders on the same page before a disaster strikes here in the Bay Area.
Organizers said that people have been telling them there is no way to be 100 percent prepared for a disaster, but they say it won't stop them from trying.