Lincoln Boulevard between Montgomery and MacDowell will close for a year and a half. That is necessary so Caltrans can dig the first of four news tunnels.
Right now, traffic coming off the Golden Gate Bridge into San Francisco stays above ground the whole way. However, a Caltrans animation shows how in about three years from now, cars will disappear into tunnels.
Construction on the first of those tunnels is about to begin.
"It's not a tunnel like Devil's Slide or Caldecott, not a mined tunnel, it's a cut and cover tunnel, you build temporary shoring walls and we basically excavate it, like an open box," said construction manager Dave Pang.
A portion of the first tunnel will run underneath the Presidio's Lincoln Boulevard, along the edge of the cemetery. That stretch of Lincoln will be closed starting on Wednesday because the construction requires the road be demolished and rebuilt later.
"The traffic throughout the presidio, is a low enough volume, so that we're not expecting any severe traffic delays," said Molly Graham, a Caltrans spokesperson.
They are wroking on a wood structure, which is one of two anchors for the new southbound bridge section that will link to the tunnel.
The piles for the bridge are about 180 feet deep, and then another 45 feet into bedrock. A giant piece of equipment is digging into the bedrock with carbide steel tips.
The 12-foot-pile cages will eventually be lowered in and filled with concrete. A Caltrans animation shows both north and southbound bridges when completed.
The new bridge will run directly above the pet cemetery, so about a month from now, Caltrans will build a special structure to protect the cemetery. It's not a protected landmark, but Caltrans recognizes the emotional significance of the place.
Sometime late next year, the new seismically safe southbound bridge and tunnel should be done. They will be put into use immediately, carrying traffic in both directions as a temporary detour. So a section of the old Doyle can be demolished and the new northbound bridge and tunnel could be built.
For a link to a map of the closure and how it will affect bike riders click here.
