Updated January 14, 2010
Originally posted February 27, 2009
UPDATE ON GOLDEN GATE BRIDGE SEISMIC RETROFIT
CONSTRUCTION PROJECT
At the February 26, 2009, meeting of the Golden Gate Bridge, Highway and Transportation District’s Building and Operating Committee an informational update on construction of the Golden Gate Bridge Seismic Retrofit Construction Project, Phase 3A was provided. Phase 3A involves retrofit of the Marin (North) Anchorage Housing and the adjacent Pylon N1. A construction contract for this Project was awarded in April 2008 and it is scheduled to be completed in 2011.
During Phase 3A, the Bridge roadway and sidewalks within the limits of the Marin Anchorage Housing will be entirely replaced (See photo below). The sidewalk replacement will be completed first. It will begin in spring 2010 with, first, the replacement of the 300 foot-long portion of the east sidewalk followed by the replacement of the 300 foot-long portion of the west sidewalk. The sidewalk work will take approximately 120 days per side. Then, the roadway replacement will proceed.
During the Phase 3A construction, the Bridge roadway and sidewalks will remain open at all times for vehicles and bicycles to cross it, although the work will involve nighttime closures of the selected traffic lanes and detours of the bicycle traffic between the sidewalks. There will be some limitations to pedestrian access on the east sidewalk. Except for the 120 days scheduled for the replacement of Anchorage Housing roof portion of the east sidewalk, the pedestrians will continue to have access to the east sidewalk across the entire Bridge. During the 120-day period, pedestrians will be allowed to walk on the east sidewalk; however, they will not be able to walk all the way across the Bridge due to the replacement of the 300 foot segment.
Additional Project Background
The Golden Gate Bridge Seismic Retrofit Construction project was divided into three phases, two of which are now completed. Phase 1 retrofit the Marin (north) Viaduct structures and was completed in December 2001 using $71 million in toll dollars. Phase 2 undertook the retrofit of the San Francisco (south) viaduct structures and Fort Point Arch. It was completed in spring 2008 at a cost of $189 million, with $112 million in federal funding and $77 million in regional and state funds.
Following the events of September 11, 2001, Phase 3 was redesigned to incorporate additional security measures to aid in protecting against manmade threats as well as to seismic vulnerabilities. Phase 3A is a $125 million project that will be funded with a combination of Bridge tolls, federal funds, and state and regional funds. Phase 3B is estimated at $260 million and is planned to go out for construction bids in 2010. It will retrofit the main span, the two main towers, and south tower pier and fender.
The race against time continues as according to the U.S. Geological Survey, there is a 62% probability of a magnitude 6.7 or greater earthquake striking the San Francisco Bay Area in the next 30 years. Once the seismic retrofit construction is completed, the Golden Gate Bridge will be able to withstand a nearby quake of 8.3 magnitude.