These little metal street tags are everywhere – flat as they are, one almost tripped up our new restaurant

A San Francisco survey tag set in the sidewalk at the corner of Chenery and Brompton.

Glen Park’s soon-to-be newest restaurant, La Cigale, is well on its way to completion. Until there was an unexpected glitch, as the San Francisco Standard reported on Thursday.

Have you ever noticed little metal tags embedded in the sidewalk? Neither had the owners. But it turns out they’re important. As San Francisco Public Works notes on its website:

“Survey monuments are essential to the precise location of all land divisions (parcels) within the City and County of San Francisco. The framework for actual physical reference points, known as monuments, has been previously established and must be preserved in order to secure ownership boundaries. The City’s monument system consists of known points that serve as the basis of reference for subsequent new and existing land subdivisions.

In San Francisco, it is the responsibility of the City and County Surveyor to ensure that the existing reference framework of control points known as monuments is maintained.”

Because the survey monuments (i.e. the metal sidewalk tags) are important reference points, if you have to dig up your sidewalk and move them then it’s important that they be replaced and replaced correctly.

If you have to dig up anything within 20 feet of one of these survey monuments, you’re required to use either a city surveyor or hire a private surveyor to ensure it goes back exactly where it’s supposed to – reestablished – and if you don’t it’s a $10,000 fine.

Hiring the city to do it can cost up to $4,455, though hiring a private surveying firm cost La Cigale cost $800.

While the San Francisco Standard story makes it sound as if no one in the construction world knows about this, a source at the City tells the Glen Park News that contractors who do excavation work are well aware of the survey requirement.

La Cigale is still on track to open this year, thank goodness. But it made us wonder – where are all these things we’d never heard of? We went looking for the tags in Glen Park and found a ton of them on the City’s map, called Mon-U-Mental, which you can see here.

But it doesn’t seem to be entirely accurate. The Glen Park News‘ intrepid reporting staff went out looking for them in the wild (ok, only along Chenery Street) and didn’t find all the ones the map says should be there. It would be interesting to know how accurate the map actually is. Maybe a great project for a high schooler?

Map of San Francisco city survey tags for Glen Park.

A San Francisco survey tag set in the sidewalk at Chenery and Brompton.

Local Glen Park historian Evelyn Rose sent along this information as well:

Here’s the history behind them and why they’re important. Many of the landmarks used for surveying during the 19th and early 20th centuries were not permanent (eg, rocks, fences, posts, stakes, structures that no longer exist). Below you can see an example from an advertisement in The Daily Alta Californian from 1881 which uses impermanent features to give the location of plots of land.

These metal tags can also serve a purpose in case of conflagration, similar to imprinting street names in concrete curbs at street corners, in case all identifiable landmarks are obliterated.