Progress update on Sunnyside Flood Detention Basin Project

Posted on November 21, 2022

Aerial view of the current state of progress at the Sunnyside Flood Detention Basin Project, showing construction vehicles on a large area of dirt.
Aerial view of the Sunnyside Flood Detention Basin Project, which is nearing completion and is expected to be operational this rainy season.

Work is progressing nicely with the detention basin at the former Sunnyside Nursery, located at 3000 Sir Francis Drake Boulevard. It is nearing completion and it will be operational this rainy season. Once completed, the detention basin will hold stormwater overflows from Fairfax Creek during peak storm events by having water spill over a side weir from the creek. The basin is designed to detain the excess stormwater, reducing flood impacts to the downstream communities. Once a storm has subsided, the stored water in the basin would be released through various outfall pipes, which can be controlled by Flood Control District staff to ensure proper timing in coordination with the Town of Fairfax staff.

The basin will reduce flood risk during 10-year and 25-year flood events, as well as reduce the flood water depth of larger storm events. A notification protocol will be developed in collaboration with the Town of Fairfax to ensure that the communities are aware of when the basin is active during a storm, as well as during the release of detained water after a storm.

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