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In Case of Fire, Look to Twin Peaks

by Greg Pabst

Andy Rooney’s voice lives in my head.

Yeah, that unmistakable cranky whine from CBS TV’s 60 Minutes seems to be always asking, “Do you ever wonder why...?”

Do you ever wonder why San Francisco has two sizes of fire hydrants? You sometimes see them facing each other across an intersection, one Stan Laurel to the other’s Oliver Hardy. And my inner Andy wanted to know why.

A fireman once gave me the first piece of the puzzle. Skinny Stan is a fairly standard model that in San Francisco runs the drinking water pumped from Chain of Lakes, a.k.a. the San Andreas Fault.

Husky Oliver, on the other hand, spouts a high-pressure stream that is essentially driven by gravity through its own piping that begins at a reservoir just below the Twin Peaks “tourist outlook.”

We all know that the 1906 fire burned unchecked for three days due to the failure of the fireplugs. The water mains broke and, tragically, there was no backup. Post E&F San Francisco felt the need to correct that quickly. The City Guides’ Sutro Forest Hike goes past the reservoir, so one May afternoon a few years ago I made a phone call to the Public Affairs Office of the SFFD to see if anyone could scare up some fun facts for me. “Oh,” I was told, “you should talk to Steve Van Dyke. He knows everything there is about the AWSS. Call him tomorrow, real early” and she gave me the number. Next morning, about seven, I make the call. You know how some people sound at work, like you’re interrupting them in the middle of something important and they’re trying to intimidate you into keeping it short? I get an abrupt “Van Dyke!”

Van Dyke? This is the guy who knows everything! Yow!

I ask a few questions. He answers with a sentence or two. A few more questions and I notice his answers are getting longer and more detailed, and he’s getting excited. About eight minutes in it’s like a Cossack dance, we’re both all but jumping up and down and shouting “HEY!”

“You got a fax machine?” he yells. “Get it ready. I’m sending you something.” About nine minutes later my Mac beeps that he’s sent me TWELVE PAGES. It’s the Mother Lode! Everything I wanted to know and more.

So here’s the bouillon-cube version. Twin Peaks Reservoir, with a ten million gallon capacity, 150 miles of high pressure mains, and 1,550 large circumference hydrants, is only part of San Francisco’s “Auxiliary Water Supply System for Fire Suppression” (begun in 1909). “The system,” says Steve’s fact sheet, “has an excellent combination of features which effectively utilize San Francisco’s hilly topography and waterfront perimeter.”

The concrete reservoir itself has a dam across its center, creating two “bays.” Each is emptied separately so that if a pipe breaks in the system, only half the capacity will be lost.

Below Twin Peaks, in Ashbury Heights, is a 500,000 gallon tank fed by the system and below that, in a tank on Jones Street on Nob Hill, is another 750,000 gallons.

But wait, there’s more!

Two pump stations, one at the foot of Van Ness (near Muni Pier), the other at 2nd and Townsend, are both capable of moving 10,000 gallons per minute (gpm) of salt water through the system at high pressure using their on-site generators to run the pumps. And if all of the above fails, there are two connections on the Bay where fireboats can also drive salt water into the system. The Phoenix can deliver 9,600 gpm and The Guardian has a pumping capacity of 24,000 gpm, the highest of any fireboat in the world!

Lastly, The City has 175 independent underground cisterns (a circle of bricks at an intersection with a manhole in the middle usually gives them away), most of them holding 75,000 gallons in case of last resort/worst case scenarios.

You never know what you’ll uncover when your inner Andy asks “Do you ever wonder....”

Now, do you ever wonder why the Muni carbarn near Balboa Park is named for Curtis Green? Do you ever wonder who Muni’s Steve Van Dyke is? I do.

Photos courtesy of Greg Pabst.

Schematic drawing courtesy of San Francisco Fire Department.

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Skinny Stan and Husky Ollie stand independent fire sentinels on San Francisco's streets

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This reservoir, just below the summit of Twin Peaks, is the primary water source for our gravity-driven auxiliary fire hydrant system.

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An SFFD engineer's schematic drawing for the Auxiliary Water Supply System for Fire Suppression

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