Remembering Loma Prieta – And Preparing for the Next Big One

Monday, October 17^th is the 27^th anniversary of the Loma Prieta Earthquake. The 6.9 magnitude quake shook the earth for 15 seconds, took the lives of 67 people and injured almost 3,000 more. There was an estimated $6 billion in property losses. We here at the San Francisco Public Utilities Commission have been preparing for the next big quake ever since.

As the owner and operator of the Hetch Hetchy Regional Water System that serves water to 2.6 million people in four Bay Area counties, we have worked for more than 10 years to repair, replace, and seismically upgrade vulnerable portions of this system as part of the $4.8 billion Water System Improvement Program (WSIP). The program itself is more than 90% complete. Our water system is safer and more reliable today than it was 10 years ago, let alone 27 years ago. Our promise is that we can deliver minimum demand to our customers within 24 hours after a major earthquake. We can make good on that promise because of WSIP.

Here’s just a few reasons why:

* The Bay Tunnel is a seismic lifeline carrying water under San Francisco Bay. It was brought into service on time and under budget in October 2014.

* The New Irvington Tunnel carries water between our East Bay and Hetch Hetchy supplies and our Bay Area Customers. Located between the Calaveras and Hayward Earthquake faults, this seismically designed tunnel allows us to take the existing 88 year-old tunnel out of service for maintenance.

* A new Bay Division Pipeline #5 connects to both of these new tunnels in the East Bay and on the Peninsula to provide greater delivery reliability to our customers. It replaces two pipes that were constructed in 1926 and 1935.

Wait, that’s not all!

We upgraded our Sunol Valley Water Treatment Plant, which treats water from San Antonio and Calaveras Reservoirs. It can now treat enough water to support our entire service territory on its own (160 million gallons of water per day) for up to 60 days after a major earthquake.

Water treatment trains at our newly upgraded Sunol Valley Water Treatment Plant

Two major transmission lines sit on major traces of the Hayward Fault in Fremont. We used cutting-edge technology on our Bay Division Pipelines 3 and 4 to allow one of them to absorb up to 6.5 feet of horizontal displacement and 9 feet of compression while still remaining in service.   

 

A slip joint at the Seismic Upgrades to the Bay Division Pipelines 3 and 4 at the Hayward Fault Crossing allows the pipe to absorb up to 9 feet of compression during an earthquake.

This work is never done. We will continue to replace and upgrade our system pipelines, pump stations, and treatment plants even after the WSIP is complete. We’ll worry about your water so you won’t have to.