What is the oldest functioning bridge in San Diego? This #seismicsaturday we feature the Quince Street Bridge.
The Quince St. Bridge was built in 1905 to connect residents of the then fast-growing Bankers Hill neighborhood to the trolley line in 4th avenue. The bridge is 263 ft long and 60 ft tall. It cost just 850 dollars in 1905 to build. The bridge has a wooden truss structure.
The bridge was originally made out of Redwood. Redwood contains a natural chemical called tannin, which makes the wood rot, bug, and fire resistant and gives the wood it’s beautiful red color. The tannin in the redwood allowed the bridge to last 82 years outdoor under the elements untill 1987.
In 1987, the bridge was suddenly closed after a city inspection found it to be “infested with termites, full of rotting wood, and generally unsafe” (McDonell 1987). A consultant hired by the city determined that the bridge should be torn down. Local residents were were up in arms about the possibility of their romantic redwood bridge being torn down and they mobilized to have the bridge saves, convincing the City to designate it as a historic landmark. In 1990, the bridge underwent a major refurbishment, in which much of the redwood was replaced by pressure-treated pine.
One can still see some of the original redwood columns on the bridge along with the original bolts from 1905 (fig. 3). The fact that these columns are still standing is a testament to the incredible durability of redwood.
The pressure-treated pine from the 1990 rebuild can be identified by the staple-sized indents (fig. 4). These indents are made during the treatment process so that chemicals, including chromium (bactericide), copper (fungicide), and arsenic (insecticide), can penetrate into the wood. These chemicals make pressure treated pine last much longer outdoors than untreated pine.
The bridge is not in pristine condition. The dirt around one of the foundations is quite eroded (fig. 5), and some of the steel strips that sister beams together are coming off (fig. 6).
The Quince Street Bridge is a beautiful and historic redwood structure. Thanks to the efforts of dedicated community citizens in the 1980s, it has been saved for generations to come.
McDonell, Patrick. “Despite Emotional Attachments, Future Bleak for Quince Street Bridge.” Los Angeles Times. 28 November 1987.