A behind-the-scenes tour of SF’s City Hall – EP.0018


Hello everyone. Welcome to Public Works TV. I’m Edgar Lopez, Deputy Director of Public Works and City Architect. Before we get started, let’s take a look at the events of this week. This week at Public Works, we launched our 18th Pit Stop in its ninth neighborhood citywide. This Lower Polk location will operate at Larkin and Myrtle streets, next to Sgt. John Macaulay Park. We came together with other City agencies and contractors at our quarterly liaison meeting to strengthen communication by discussing processes, expectations and opportunities of working in the City. To further the department’s efforts in achieving zero waste, our construction management and materials testing lab partnered with Central Concrete to test a new product on our curb ramps and road base in the Inner Sunset. This product recycles wet, unused concrete back to the plant where it is mixed with another batch and an additive for reuse on other projects. Our crews were also out along Cargo Way paving a protective bike lane to make sure cyclists have a smooth ride. Today, we’re at beautiful City Hall in San Francisco As many of you know, San Francisco City Hall is one of the finest examples of baroque architecture, not just in San Francisco, but in the country. What you may not know about City Hall is in its current location, this is the fifth city hall that San Francisco has built. It was built after the 1906 Earthquake. The previous city hall was damaged and demolished. The building took roughly two years to build and the voters approved the bond for $8 million to buy the land and build the building. The construction totaled around $3.5 million. Imagine that in today’s dollars. For $3.5 million, the City was able to build this magnificent building in a record time. The city hall was damaged after the 1989 Loma Prieta earthquake. Public Works’ role was to restore and seismically upgrade the building. We had a team of consultants and architects, City architects and City engineers who worked on the project. Our role was to define the scope of the renovation and do a full seismic upgrade and modernization. So there’s some very tricky things about City Hall that you will enjoy observing next time you come back and we’ll point those out to you. One of the most fascinating things about City Hall is that it’s base-isolated. What that means is that the weight of the building, every column was placed on a base-isolator. This is a quarter-size base-isolator it has two large plates of steel at the top and at the bottom and the middle is made up like a cake: layers of rubber and layers or steel. And when there’s an earthquake, the energy is dissipated through the rubber and the steel plates. So this is connected to the ground and this is connected to the building. And the building will experience a lesser-magnitude earthquake than the ground will, as a result of having the base isolators. So while you may come up the front stairs of City Hall many times, something that you may not have noticed is these are floating stairs. They are not connected to the ground because the building is base-isolated. And the concept is that in case of an earthquake when there’s movement, the building will move separate from the ground. So to stairs can move in any direction up to 24 inches. So this represents the maximum distance that the building’s expected to move in case of an earthquake. And this is a flex joint that will allow the building to move. So the building has a moat.
I don’t know if you ever noticed that. Again, on this concept of base-isolation, in case of a massive earthquake and you were here, you could see the building coming close to you and moving away. When you’re downstairs at the Light Courts, you get this beautiful glowing amount of light that comes in. What we did for the renovation is remove metal deck and concrete that was put here. Nobody really knows, but what the stories that I heard is that during the war, they wanted to darken City Hall. To make sure that we wouldn’t have this amount of light glowing. We consulted with a party planner when we were doing this of how people might set up the space for events, and they told us that at the two ends is most likely where you would have a band, So the rigging points that we put in there can carry 2,000 pounds of weight, which is equivalent of a full-size car. And that’s meant for hoisting up speakers and equipment and be able to have bands that set up on either side of the Light Courts. That happens also on the North Light Court as well. The other scopes of work included how to modernize City Hall. We ended up putting emergency generators for backup power, we ended up putting miles and miles of cable to allow for internet connection. As you know, the building was built over 100 years ago and it had not received any major upgrade to modernize it. Today, when you walk through City Hall, you see the grandeur of a building of baroque style, but it has the functionality of a modern building. When we get to the second floor, we had to add ramps after the seismic renovation to make it ADA-compliant. There was no way of having somebody being able to go from the second floor to the Board Chambers. And so we needed to add those ramps. So these lights, where some of them were broken after the earthquakes they’re replicas that were fabricated in the South of France, where the original lights came from. The steel pieces that you see that are red in color, that’s the primer and that’s how you can differentiate the new steel that was put as part of the seismic upgrade, versus the historic structure. One of the biggest challenges of doing the work at this level was how to get those pieces of steel because there’s not a lot of room, as you can tell. So I remember seeing workers with the little rigs that they had trying to get the steel in place, and how to connect it, get it into these tight spaces and do the welding. We’re at the top of the dome area in City Hall enjoying this gorgeous view that is uninterrupted, giving us a clear view of San Francisco. At City Hall, looking at the historic details of the building in contrast with the modern buildings that are going up in San Francisco. It’s a very special place to be. And we are very proud of our City Hall. I’m Edgar Lopez, thanks for watching Public Works TV. I am Devin Macaulay, I keep SF on budget. I am Public Works. Together, we are Public Works. People sometimes ask, “Why is City Hall monochromatic?” Why was color not introduced as part of “the design?” The architect’s vision of having it monochromatic was that in very special locations, it would highlight the gold and blue that is used for details around the lanterns, the handrail and accentuate that.

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