Scaffolding is set to arrive by Wednesday at the Golden Gate Bridge so workers can do something that has never been done since the span opened: renovate the massive main cables.
The bridge — opened in 1937 — has two main cables that pass over the tops of the two main towers and are secured at either end in giant anchorages. They are the steel strings that hold the bridge together and support the roadway.
“We redid the vertical suspender cables in the 1970s and the roadway itself in the 1980s, but this is the first time the main cables will be renovated in this manner,” said Mary Currie, bridge district spokeswoman.
Each of the 3-foot diameter cables is made up of 27,572 individual galvanized steel wires wrapped inside a casing, which is painted for protection from the harsh elements. The length of one main cable is 7,650 feet, and 80,000 miles of individual wires were used in their construction. Along with the suspender cables and accessories, the main cables weigh 24,500 tons.
While the cables are tested for strength, they have not been completely painted in more than 70 years.
Once the scaffolding arrives midspan and is set up in the coming weeks, crews will embark on the three-year project, which will include cleaning the exterior of the main cable and roughing the surface so new sealing paint can be applied, as well as making any additional repairs.
The work will begin on the west side main cable. Scaffolding will be erected along the 400-foot-long segment from midspan south toward San Francisco. Workers will then work in 60-foot segments underneath a tarp that will keep lead paint chips coming off the cables from spreading.
They will spend up to six months renovating the 400-foot section. The scaffolding will be disassembled and reassembled along a 400-foot-long segment heading north from midspan toward Marin. Workers will then renovate that segment for another six months. In the coming two years, the rest of the cables will be renovated as well.
While this work is under way on the west side cable, the fixed scaffolding will reduce the west sidewalk width from 10 feet to seven feet for the 400-foot stretch. Bicyclists may be asked to walk their bikes through the work area.
The scaffolding is costing the district $100,000. Initially the district had planned to contract the work out at a cost of $30 million, but will now rely on its own workers for the project.
“This is a great project for us to take on in-house, especially in the face of the financial challenges that so many public agencies are facing,” said Denis Mulligan, bridge general manager.
Via: www.mercurynews.com