The HetchHetchy Regional Water system, operated by the San Francisco Public Utilities Commission (PUC), carries water to 2.6 million customers in the Bay Area. How it does that is remarkable – remarkably simple, says PUC Water Resources Manager, David Briggs.
“Because it's gravity driven, largely,” Briggs says, “the Romans, if they were here today, they could probably understand how our system works.”
That’s thanks in part to how old the system is. It’s not Roman-empire old, but some of the pipes carrying this water were put in the ground more than a century ago, which means sometimes they break.
There are approximately 1,240 miles of water supply pipes running under San Francisco. Fifteen percent of them are more than 100 years old. The PUC is currently replacing the system’s aging pipes at a rate of about nine miles per year.
The PUC’s David Briggs says it can be hard to pinpoint which pipes need upgrading the most.
“We can't dig them all up and saw them in half and look at the look inside ... and see how much pipe thickness is left so we use a lot of indirect methods. It's sort of an art more than a science right now,” says Briggs.
According to Briggs, about a hundred water mains bust every year. One broke in late January near the Panhandle of Golden Gate Park and flooded the DMV next door. Another one busted at the beginning of this month in Glen Park and shut down a nearby Muni line. Briggs says every break is different.
“Sometimes it'll just manifest as a wet spot on the pavement and it'll be an annoyance somebody might slip on it … other times somebody will cleave off a fire hydrant and put a sixty foot geyser in the financial district.”
According to PUC data, about eight percent of the city’s water supply is lost to leaks. And in a drought, every drop counts. When Governor Brown declared the drought a state of emergency last year, the PUC started asking customers to cut back on water use by 10%.
“Leaking pipes and wasted water, of course, flies in the face of that and the drought just magnifies it,” Briggs says. “Everybody is under the microscope right now.”
If the drought gets a lot worse, Briggs says we could see something like mandatory water cutbacks, meaning customers would get a set amount of water. Briggs says it’s hard to predict when that could happen.
“If it stopped raining in California for years at a time … we would be in a world that we’ve never seen before,” Briggs says. “Things that may sound improbable or strange now may not be if precipitation in California is just too low.”
To prepare for that world, the PUC is expanding the capacity of the Calaveras Reservoir to catch more of any rain that does fall. The agency has also started looking underground for drinking water instead of relying just on what comes from the mountains. And over the next couple of years, the PUC will ramp up its repair rate of San Francisco’s aging pipes to 15 miles per year.
