San Francisco’s Long History of Catastrophic Sinkholes

Sinkhole on Kirkham, April 2021

We all hope that the pandemic is starting to loosen its grip on San Francisco. As it does, and we emerge, blinking, into the light, we will be presented with the obvious question: what existential threat should occupy our minds now? I would like to propose that we spend our time worrying about sinkholes.

San Francisco has a long history of catastrophic sinkholes. California itself exists on ever-shifting ground. From earthquakes to the flow of mud and silt from the Sierras to the bay, the state was constantly re-inventing itself out of dirt even before humans arrived. San Francisco is built on sand dunes and crumbling rock. The landscape is eager to devour anything, cars, buildings, even people.

A montage of sinkholes eating vehicles

During the gold rush, miners used water cannons to wash away entire mountains. So much dirt and silt flowed into the bay as a result that its depth was reduced by up to a foot a year before the practice was banned. It was one of the first environmental protection regulations in the country. This shows that when water and sand mix, the result is dramatic, and water and sand mix in San Francisco a lot.

Take the Valencia Street sinkhole that opened up after the great quake of 1906. The temblor broke a water main, and the four-story Valencia St hotel was swallowed up by the earth, becoming a single story. Later, the continuing flood of water opened up a sinkhole beneath the street. Reports claim that as many as forty people drowned.

The 1995 Seacliff sinkhole

Another spectacular sinkhole opened up when a sewer burst in Seacliff in 1995. Not only is San Francisco built on sand, but its sewer system is somewhat idiotically combined with its storm sewer system, with sometimes catastrophic results. If you enjoy shadenfreude over the plight of rich people, you’ll enjoy this amazing video of a mansion being sucked into the ground.

While it’s uncommon (though not as uncommon as one would hope) for entire houses to be consumed by sinkholes, cars are another thing. Cars are hors d’oeuvres for San Francisco sinkholes. It’s not hard to find pages and pages of photos of perplexed San Francisco residents staring at a car or truck being consumed by a sinkhole…like this one. Or you can just do a plain old google search. For the sinkhole aficionado, there is really no greater pleasure than the image of a man in an orange safety vest pointing at an SUV in a sinkhole. I might go so far as to suggest that we make that our city flag, instead of the current image of a flamboyant turkey being roasted.

Sinkholes can eat entire streets. Like 34^th Avenue in 1960, when an entire block of street collapsed into the sandy earth. Houses are not uncommon fodder for sinkholes either. As well as the above mansion, a 50 ft wide sinkhole demolished a house on Olympic drive in South San Francisco in 1981.

On the corner of my block, at the intersection of Folsom and 13^th, there’s a spot under the freeway where water comes down from the overpass during rain storms. Predictably, the sand underneath Folsom washes away and a sinkhole opens up. Just as predictably, the city comes out and pours tar into the sinkhole. The tar is slowly consumed by the insatiable sinkhole, and the city comes out again in 6-12 months to repeat the process. That cycle has been repeating since at least 1999. A public records request showed 20 reports of a cave-in at just this one corner since 2017!  It’s one of many sinkhole feeding projects around San Francisco that keep DPW workers employed and probably inflate the price of tar.

Nom nom, street eat truck

So as you’re walking around the city wondering who might have COVID, relax. There’s a good possibility that the earth will open beneath you and swallow you whole. The sand beneath San Francisco demands a sacrifice. It might be you, it might be a Hyundai or it might be an entire mansion, but rest assured, more gaping maws will open in the streets of San Francisco. That should give you something new and exciting to worry about. Something that, we all agree, we could use about now.