Center Boulevard Bridge succumbs to sinkhole


Ezra Thaler

Construction signs redirect drivers away from the sinkhole on Center Boulevard towards Bridge Avenue in Downtown San Anselmo.

On Monday, April 11, at approximately 4 p.m, part of the Center Boulevard Bridge in downtown San Anselmo caved into an unexpected sinkhole. Parts of Center Boulevard closely surrounding the bridge were swiftly closed off by the Town of San Anselmo. Construction crews are already enforcing their new reconstruction plan to prevent future sinkholes in the area.

Temporary gates restrict residents from getting near the sinkhole as construction crews work on fixing the street. (Ezra Thaler )

San Anselmo’s town administration received a report from the Central Marin Police Department shortly after the discovery of the sinkhole. Following this notice, San Anselmo’s Public Works Department, which includes the engineers that construct all bridges in San Anselmo, came to the site of the sinkhole to determine the cause.

“[The Public Works Department] got down into the creek and followed the sinkhole down and discovered a whole bunch of degradation under that bridge that was being undermined by the creek for years. Little by little the creek has eroded away some of the supports that help hold up the roadway and the bridge,” said Dave Donery, Town Manager of San Anselmo.

No vehicles or pedestrians were harmed during the sudden concrete collapse. To accommodate for the commonly used bridge and thoroughfare being closed, vehicles will now have to use a detour to access the hub, which involves only two extra turns through Bridge Avenue from the original route through the Center Boulevard Bridge. An estimated time of reopening the closed-off street has not yet been determined by the Town Administration of San Anselmo.

“The structure underneath [the bridge] will be completely rebuilt, we have a crew out there now, they have done an evaluation and have made a plan to fix it,” Donery said. “[The plan is to] go in and pour concrete walls that will be used to hold up the bridge supports.”

The reconstruction aims to solve and prevent any future sinkholes or hazards of that degree. The additional concrete will restrict any water from eroding the supports under the Center Boulevard Bridge.