While tourists flock to see and photograph the iconic towers of the Golden Gate Bridge every day, it has been five years since anyone has taken a dip and looked below the water line.
That will soon change, as the Golden Gate Bridge Highway and Transportation District is set to approve a $262,000 contract today with Infrastructure Engineers LLC to conduct routine inspections and growth removal on the bridge’s concrete base and foundation.
The Golden Gate Bridge is part of the National Highway system and is required to conduct an underwater inspection every five years.
If the contract is approved, vessels could be in the water with high resolution scanning equipment and penetrating radar known as ‘side-scan sonar’ as soon as March, according to John Eberle, deputy district engineer. They will scan for any ‘gross defects’ or areas of concern in the structure and foundation.
Once scans are complete, they will send in the divers.
“It is an amazing thing to watch, and the work they do is fascinating,” said district board member Brian Sobel.
Speaking with the San Francisco Examiner on Thursday, Eberle explained just how the divers will inspect The City’s International Orange-colored icon: Going down in teams of two in dry suits equipped with a supplied air system, with air pumped through a hose, divers will begin the slow work of inspecting the base. Four to five tenders will stay at the surface monitoring the divers and their air flow through a radio system and a camera mounted on the diver’s helmet. They maintain constant communication throughout the dive.
Divers will mark out a grid on the 700 square feet of concrete that makes up the base of both towers, which they will use to coordinate a more detailed inspection along with growth removal. Working in five hour shifts, the process is expected to take at least two weeks to complete.
Despite the sophisticated technology, much of the work will have to be done by hand. Poor visibility alone will force the divers to conduct the majority of the inspection through touch. They will remove vegetation growth on the concrete using wire brushes, scrub pads and putty knives.
The last inspection conducted was in June 2014, according to Eberle. It did not yield any significant concerns with the foundation and officials anticipate another clean bill of health this time around.
That’s because the bridge was constructed in an era when infrastructure was built to last, said Denis J. Mulligan, general manager of the bridge district.
“I can tell you why it’s in good shape. In the 1930s, those that went before us were very forward thinking and cutting edge,” he said.