2nd layer of quake protection
City’s emergency water system designed to withstand disaster
All it took was 15 seconds. When the Loma Prieta earthquake ripped through the Bay Area 26 years ago Saturday, the damage was almost instantaneous. The doubledeck Nimitz Freeway in Oakland collapsed, and the soil underneath the Marina liquefied, causing gas main ruptures and structural fires. Thousands of people were injured, and 63 died.
San Francisco rebuilt, and the areas of the city most vulnerable to quakes were strengthened. That included the auxiliary high-pressure firefighting system, a secondary source of water that can be used to fight fires if hydrants are shaken offline. It was constructed in 1913, in response to the 1906 earthquake.
But until a few years ago, the system was considered only 47 percent reliable after a major rumble. To improve it, voters approved two Earthquake Safety and Emergency Response bonds, one in 2010 for $104 million and another in 2014 for $55 million. Another bond is planned for the ballot in 2020.
Together, the work paid for by the bonds will bring the reliability up to more than 85 percent. So far, there are 16 new cisterns for water storage, and five more are under construction, almost doubling the number in these areas.
San Francisco is one of two cities — the other is Vancouver, British Columbia — in North America to have a second water system separate from the pipes that deliver water to households and buildings, though Los Angeles officials are considering one. The high-pressure system includes more than 200 cisterns, pump stations, storage tanks and reservoirs, as well as about 120 miles of pipes.
Seeking equal protection
Locals are often surprised to learn that there are two water systems running under their feet, said David Briggs, Public Utilities Commission local and regional water system manager.
“The system is unique by definition,” he said. “There’s very, very few of them. San Francisco burned down six times prior to the 1906 earthquake, and the city’s leadership didn’t want that to happen again. The vast majority of the system is concentrated in the area that was developed during that time, so that’s the northeastern part of the city.”
Before, the west and south sides did have what’s called a domestic hydrant system, but no auxiliary hydrants. The difference: Auxiliary hydrants are stout and wide in comparison to the taller and thinner domestic hydrants, and their water is non-potable and highly pressurized, meaning firefighters don’t need a truck to pump it.
Hoses can also be dropped directly into cisterns, which are marked by a brick square or ring in the middle of an intersection, or into Sunset Reservoir or Lake Merced. The next step will be to create easy connection points for these water sources.
“We are trying to find reasonable alternatives that allow us to arrive at equivalent protection for all parts of the city,” said Charles Higueras, Public Works’ earthquake bond program manager.
“It’s not that people on the west side are unserved, but we want to make sure they are as equally served as people in the upper part of the city. We want to shoot as close to 100 percent as we can get.”
Constant evolution
The auxiliary high-pressure firefighting system is more durable than the city’s normal water system, which means it stands a better chance of surviving an earthquake intact. Higueras described it as the difference between a “lightweight car and a durable construction-grade truck.”
“It’s built to last and to survive any kind of earth movement,” he said. “We are putting a lot of energy into understanding every variable that could impinge on the effectiveness of it. Having a system ready to go for firstresponse emergencies is absolutely necessary.”
Even though residents often notice only the construction and obstructions that back up traffic, the projects around the city are making it a safer place. That’s particularly important for the west side because many of the homes are connected wood buildings, Supervisor Katy Tang said.
“If there was a huge fire, the impacts would be very severe,” Tang said. “We have had this great opportunity to really strengthen the west side, and we have come a long way. As a city, we are constantly evolving how we think about emergency preparedness.”
Fortunately, she said, San Francisco is usually ahead of the curve. That helps prevent disasters before they happen.
“The anniversary of Loma Prieta is such a good reminder of what has happened in our past and how important it is to take steps early to prevent a huge fire from happening again,” she said. “We are taking steps to make sure all of our residents will be safe. Many other cities around the world still have a lot to learn.”
“It’s built to last and to survive any kind of earth movement.” Charles Higueras, S.F. Public Works Department