Drones Help Pave a New Path to the Golden Gate Bridge
Five years ago construction began on San Francisco’s billion-dollar Presidio Parkway project. This weekend, following a monumental effort by construction crews that included shutting down a critical stretch of freeway, and lots of commuter grumbling, the new Presidio Parkway opened to traffic for the first time.
The aim of the Presidio Parkway project was to entirely replace Doyle Drive, the roadway that connects the Golden Gate Bridge to San Francisco and which the Federal Highway Administration had declared “functionally obsolete.” Doyle Drive was originally built in 1936 to coincide with the opening of the Golden Gate. It sits between the San Andreas and Hayward faults, and the FHWA had recently awarded its bridge a functionality rating of 2 out of 100. The Presidio Parkway project that would replace it would eventually take more than five years, consist of a system of alternating bridges and tunnels and cost one billion dollars. Construction also had to account for serious seismic concerns in the area, and had to be accomplished without disrupting the flow of traffic into and out of the city or the fragile and historic Presidio and Golden Gate National Park, which the parkway passed through.
Daunting to say the least.
Enter Tristan Randall and Autodesk. Autodesk makes state-of-the-art design and engineering software that, among many other purposes, helps construction companies visualize and plan complex projects like the Presidio Parkway. Over the past five years the company helped to visualize the schedule and mitigate the environmental impact of the construction. They did this in large part by bringing the physical world back into the digital world—using scanning technology to generate digital 3D models of the construction phases as they unfolded.
“Our construction clients are obsessed with drones,” Tristan told me. We stood in a lawn at the edge of San Francisco’s Presidio, a campus of red brick barracks and offices, which for over 200 years served as a military base but is now a national park. A Solo humming over our heads, Tristan pointed out the system of bridges and half-buried tunnels, construction workers bustling over them in hard hats and day-glo vests. Tristan also wore a highlighter-yellow construction vest and a hard hat, and he had to speak up to be heard over Solo’s buzz, just as you would imagine the workers were speaking up over the equipment on the parkway.
“These people understand that drones don’t just get aerial images,” he continued. “They can collect all sorts of data that allow us to fully digitize a site—photogrammetry, taking insanely accurate volumetric measurements. With a drone you can monitor what’s happening on-site daily, even hourly, and you can attach that data to schedules that help project managers deconflict and plan ahead. The technology is changing our entire approach to construction.”
When asked about the special challenges of this massive project, Tristan emphasized the environmental impact. “The parkway passes through a national park,” he said. “So we’ve had to take that into account. There are pretty significant biological and seismic elements to consider, too. Preservation.”
I recalled passing a pet cemetery on my ride in—a relic of weeds and tall grass caught between two onramps and wrapped in orange mesh fencing. The concrete braces of a new bridge passed at about shoulder-height above the tiny tombstones. A small hand-painted sign implored passing traffic to “Preserve the Presidio Pet Cemetery!”
For three days this weekend this same traffic impatiently crawled by the cemetery while the last leg of the project was completed. The new Presidio Parkway opened to traffic yesterday, right on schedule, thanks largely to Austodesk’s exactitude. Over the next year workers will blanket the tunnels with earth, grass and trees, extending the Presidio’s lawn all the way down to the bay and transforming a militaristic freeway into a spectacular parkway and a new entrance to San Francisco.
But you can’t help looking just beyond the park to the Golden Gate and wonder—what about that one?
The billion-dollar Presidio project is just one small chapter in a massive and complicated narrative of our crumbling national infrastructure. The Golden Gate Bridge, for instance, has also been declared “functionally obsolete,” with a structural rating of 11. It sits between the same fault lines that the old Doyle Drive viaduct did.
We have a long and difficult project ahead of us. Looking at national bridge ratings the urgency becomes apparent, and frankly a little unnerving. However, powerful new technology from software companies like Autodesk, in collaboration with the software and hardware of 3DR’s drones, will do a lot to help us get where we need to be faster and safer.