Unsettling news for Marin commuters: The Golden Gate Bridge is the only bridge in the state that has not completed mandated seismic retrofit work, nearly 30 years after the Loma Prieta earthquake woke up many state officials to the need for that retrofitting. As CBS 5 is reporting, the delays have included issues with design, and the estimated cost for retrofit work on the bridge's main span: $600 million.

All other bridges in the Bay Area have been either retrofitted or replaced in the years since 1989, most recently with the eastern span of the Bay Bridge — the only bridge to suffer serious damage in the quake — finally getting replaced after 25 years of argument, delays, and construction.

And just to give you an idea about how slow these processes can be, Golden Gate Bridge, Highway and Transportation District GM and CEO Denis Mulligan tells CBS 5 that 9/11, an event that happened almost 16 years ago, caused plans for retrofitting the bridge to be put on hold — presumably as money was funneled instead toward securing the bridge against terrorist threats.

The Golden Gate Bridge, Highway and Transportation District is its own, independent, regional entity, which uses toll money from the bridge to do its own maintenance on the bridge, so therefore state or federal funding for the retrofit work is not necessarily going to come easy — this despite the fact that this is the most recognizable and beloved landmark of all the state's bridges.

Some retrofit work on either ends of the bridge has been completed over the years. Mulligan explains to CBS 5, "We have gone through and retrofitted the most vulnerable parts of the bridge first. So, today, if you are on the bridge in the mother of all earthquakes, you will be safe.”

In an earthquake, therefore, bridge officials expect that the bridge would survive without collapse, but it could still withstand enough damage that it could end up being closed to traffic for a lengthy period after.

It's unclear how much closure time would be required for the seismic work, but that work is expected to take six years, and officials are hoping it can begin in 2018 once funds are secured.

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