Water from Lake Merced is being counted on as a source for fire fighting in case of an earthquake as…

The Sunset Reservoir South Basin, seen empty in July 2019. The reservoir is one of several supplies of fresh water…

A large fire hydrant on Haight Street that is part of the S.F. Fire Department’s Auxiliary Water Supply System. The…

A large fire hydrant on Haight Street that is part of the S.F. Fire Department’s Auxiliary Water Supply System. The system, built in 1909 following the 1906 earthquake to supply reliable and high-pressure water for firefighting following an earthquake, was never extended to the westside and southern reaches of The City. (Kevin N. Hume/The Examiner)

The Sunset Reservoir South Basin, seen empty in July 2019. The reservoir is one of several supplies of fresh water that the SFPUC calls to rely upon for fire fighting. (Théophile Larcher/Special to The Examiner)

Water from Lake Merced is being counted on as a source for fire fighting in case of an earthquake as…

The Sunset Reservoir South Basin, seen empty in July 2019. The reservoir is one of several supplies of fresh water…

A large fire hydrant on Haight Street that is part of the S.F. Fire Department’s Auxiliary Water Supply System. The…

Is San Francisco ready for the next big one?

Another major battle over the city’s infrastructure centers on the auxiliary network of high-pressure water pipes designed to squelch fires that pose an enormous risk following a major quake.

A small but fervent group of activists is pushing the city to hasten and bolster its efforts to expand that network of pipes and ensure enough water can feed them. They allege that a plan recently released by the San Francisco Public Utilities Commission could fail to stave off catastrophe because it would limit the westside’s water supply only to freshwater sources, like Lake Merced, instead of investing in costly infrastructure to pull water from the sea.

City officials counter that to pull water from the Pacific Ocean would be massively expensive, arduous to permit, and isn’t necessary to offer adequate protection. They’ve charted a different course, which they say offers the same firefighting capacity at a lower cost.

The plan isn’t fully funded, and the Public Utilities Commission, which oversees the system, has yet to identify where the money will come from.

Westside activists warn that they’d be getting a second-rate version of the protection already enjoyed by residents of the northeast corner of San Francisco.

It’s a fight without a finite deadline, as no one is certain when the next earthquake on the scale of 1906, or even 1989, will shake San Francisco.

Those calling for aggressive preventive measures imagine a city once again on fire, unable and unprepared to tap into the endless supply of water that surrounds it on three sides.

“We have to have access to all the water we could possibly need so we don’t burn down again,” Nancy Wuerfel, among the loudest community advocates, told a Board of Supervisors committee during a hearing to discuss the PUC’s plan in April.

San Francisco Supervisor Gordon Mar, who represents the Sunset District, has committed to pushing officials to find ways to fund the expansion of the emergency firefighting system.

But in a city with competing and daunting infrastructure needs, he’ll have to make a compelling case.

The Public Utilities Commission’s more restrained plan to cover the rest of The City, which would eschew seawater and pull primarily from Lake Merced to fight fires in an emergency, would cost an estimated $4.1 billion to complete by 2046. The cost of building out a system that pulls seawater from the westside would be $5.7 billion.

Such an argument is likely to center on the assumption that no matter how expensive it is to build out the complex network of pipes and a supply of water to fill them, repairing the damage from a severe earthquake and subsequent blazes will likely cost more.

The U.S. Geological Survey estimates that there is a 72% chance that the next earthquake of a magnitude 6.7 or greater will occur in the next 30 years. (For reference, the 1989 Loma Prieta earthquake that killed 67 people and caused more than $5 billion in damage was a 6.7).

A significant source of damage in 1906 was caused not by the shaking, but by the subsequent fires. The quake split gas and water lines, leaving the city a powder keg while severing its means to squelch the flames.

A large fire hydrant on Haight Street that is part of the S.F. Fire Department’s Auxiliary Water Supply System. The system, built in 1909 following the 1906 earthquake to supply reliable and high-pressure water for firefighting following an earthquake, was never extended to the westside and southern reaches of The City. (Kevin N. Hume/The Examiner)

Built in the years immediately following the 1906 quake, The City has an auxiliary water system consisting of some 135 miles of high-pressure pipes designed to withstand an earthquake, ensuring continued water supply in an emergency.

It relies on a supply of freshwater stored in more than 200 cisterns and reservoirs, backed up by two seawater pumping stations in the East Bay that have been used only twice – once in 1983 during maintenance and the second an hour after the 1989 earthquake.

But it’s not just for fighting fires after a natural disaster – the high-pressure pipes are tapped about 10 times a year to fight major fires.

The problem, as highlighted in a 2019 report by the city’s Civil Grand Jury, is that the emergency firefighting water supply mostly serves the northeastern quadrant of the city.

That report implored the city to “take prompt and aggressive action to expand and enhance our defenses against the inevitable fires following an earthquake before it is too late.

“All parts of the City – north and south, east and west, rich and poor, downtown and residential neighborhoods – deserve to be well protected against this catastrophic risk,” the report stated.

In response to the report, the Board of Supervisors declared a state of urgency and tasked The City with creating an action plan to expand the emergency firefighting water system.

City officials are working to extend reliable fire coverage to unprotected areas of the city.

Unlike the city’s existing auxiliary water system — which serves a single purpose of fighting fires – the plan for the new system calls for a potable emergency firefighting water system. During normal times, these pipes will be used as transmission mains for drinking water, but they will be automatically pressurized following an earthquake. The pipes would revert to normal pressure and supply drinking water after fires have been dampened, according to the PUC. The potable emergency water firefighting system would be similar to that used in Tokyo, Japan, and has proven effective.

“They’re one of the few places in the world that has the seismic challenges and the density that San Francisco has,” John Scarpulla, the PUC’s manager of local and regional policy and government affairs, explained during the hearing.

The city would add to its existing supply of potable water to be able to meet the demand for water in an emergency.

“This system performs, and it meets the fire demands throughout the city in a robust way,” Scarpulla said.

But those fighting for equal protection of the westside note the PUC’s plan doesn’t call for a fully separate, auxiliary supply of water like the northeastern corner of the city can rely on.

“You cannot put all of your eggs in one basket,” Wuerful said.

The activists are also hoping the PUC will install new pump stations that can draw from the effectively endless supply of saltwater sitting next to Ocean Beach, rather than rely on potable water sources.

But the cost of installing two such wells would be prohibitively expensive, according to the city, and the process of permitting them in the state of California could take decades. They would be built in a tsunami zone with shifting sands, and the corrosive saltwater could not be allowed to sit stagnant in pipes.

The Sunset Reservoir South Basin, seen empty in July 2019. The reservoir is one of several supplies of fresh water that the SFPUC calls to rely upon for fire fighting. (Théophile Larcher/Special to The Examiner)

City officials have faith that Lake Merced, along with smaller backup potable water sources, is sufficient to cover the westside.

The PUC report notes that Lake Merced “has an estimated storage of 1.7 billion gallons, providing an essentially unlimited supply for firefighting.”

Some of the city’s plan is funded through voter-approved bonds, but much isn’t. Implementing a costlier version, by pulling from the ocean, would only exacerbate the funding challenge.

But to Wuerful, the cost is worth it.

“What projects are more important than saving lives, property and businesses with proven technology and unlimited seawater, and preserving our locally stored drinking water for hospitals, human uses and sanitation?”

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