San Anselmo Flood Risk Reduction Project update, November 2020

Posted on November 1, 2020

demolition activity
Before and during demolition

The first part of the Sunnyside Detention Basin construction was completed ahead of schedule in mid-November. Work included demolition of all the existing buildings and structures, stripping and stockpiling gravel and topsoil to be re-used at the site, and excavation and off-haul of approximately 20,000 cubic yards of earth. The site was covered with mulch and left in a stable state for winter.

The team is working hard to put the final plans out to bid in Spring 2021 to construct the remaining elements of the detention basin, including:

  • A flow diversion structure and gate with a control building
  • Side weir
  • Embankments around the basin
graded surface
After: graded, with erosion control installed

The project is expected to be completed and fully operational in late 2021 or early 2022.

Excavated materials will be trucked off site from the Sunnyside Basin through San Rafael via 2nd/3rd Street to and from Hwy 101 to Gnoss Field in Novato, where it will be stored and utilized for levee & flood mitigation work. Up to 10 truck trips per hour will take place between 8 a.m.  to 6 p.m. Overflow trips may use a West Marin route.

Read an article in the Marin IJ about the project.

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