The Seismic Upgrade of Bay Division Pipelines

A Critical Upgrade Beneath A Highway
By Bryan Dessaure and John Prete | February 2014, Vol. 69 No. 2
View inside the slipline work area.

How do you replace two regional water delivery pipelines that run directly underneath a major interstate freeway and lay across an active earthquake fault?

This is the unique construction and engineering challenge that the San Francisco Public Utilities Commission (SFPUC) is facing during the current Seismic Upgrade of Bay Division Pipelines (BDPL) Nos. 3 & 4 project.

Each day, water from Hetch Hetchy Reservoir in Yosemite National Park travels by gravity through a regional system of pipelines to people and businesses in the greater San Francisco Bay area. This water journeys 167 miles and crosses three active earthquake faults along the way. In the event of an earthquake, a break could sever this liquid lifeline, resulting in an interruption to water delivery for customers that could last for days, weeks or even months.

In 2002, the SFPUC approved the $4.6 billon Water System Improvement Program (WSIP) to repair, replace and seismically upgrade aging pipelines, tunnels, reservoirs, pump stations and storage tanks, thereby improving the system’s reliability for 2.6 million customers in the Bay Area.

“It is just a matter of time before the next major earthquake hits the Bay Area, so we are literally in a race against time to safely rehabilitate and upgrade our extensive water infrastructure so that we can continue to provide reliable water service to our customers in the Bay Area,” says Water System Improvement Program Director Dan Wade.

The project's proximity to a busy commuter interchanges poses unique construction challenges.
seismicart2.jpg

In all, the WSIP includes more than 80 projects spanning seven counties from the Central Valley to downtown San Francisco, and is currently 80 percent complete. One of these projects is the Seismic Upgrade of BDPL Nos. 3 & 4. In a compact half mile area in Fremont, this project will employ an impressive array of construction and engineering solutions.

Crossing the Hayward Fault
Installed between 1952 and 1967, the original Bay Division Pipelines Nos. 3 & 4 are two of four major regional transmission pipelines that currently deliver water from the SFPUC’s regional system and Alameda Creek Watershed facilities to the San Francisco Bay Area. BDPL Nos. 3 & 4 are 6.5 and eight-feet in diameter respectively, extend mostly underground for 34 miles around the south end of San Francisco Bay, converge at the Stanford Tunnel in Palo Alto and reconnect with BDPL Nos. 1 & 2 at the Pulgas Portal entrance to the Pulgas Tunnel just west of Redwood City.