Sunnyside Nursery Flood Diversion & Storage Basin


Sunnyside Nursery Flood Diversion and Storage Basin (FDS) is located at 3000 Sir Francis Drake Boulevard.  During peak water flows from the creek, this basin will store the flood waters until the water can release back to the creek naturally. This reduces flooding impacts in Fairfax.

An element of this effort is the replanting of native grasses, trees, etc. along the creek and basin, and at the San Geronimo Commons Site located along San Geronimo Creek west of Woodacre. This is required to comply with California Environmental Quality Act (CEQA) mitigation measures and as a condition of natural resources permits. This work will take place in early 2024.

Timeline and Status

  • Environmental Impact Report Approved 2018
  • Construction of Diversion Basin Completed Summer 2023
  • EIR Addendum #1 completed Spring 2023 (FDS changes addressed)
  • EIR Addendum #2 completed late 2023* (Building Bridge 2 changes addressed)
  • Riparian Habitat Planting 2024

An Environmental Impact Report (EIR) under CEQA was approved in 2018. The detention basin was constructed in the summer of 2022 and was fully functional during the atmospheric river (AR) events of the winter of 2022/23. However, the basin only fills with water when there is overflow from the creek, which did not occur during those winter storms.

An addendum to the project EIR was approved in the Spring 2023 to address the needs for additional mitigation planting due to the redesign of the diversion structure in the creek. A second addendum was completed in late 2023 to address changes related to the Building Bridge 2 elements*. The second addendum had no bearing on the FDS component. The final design, right-of-way and permitting phase is currently underway and is slated to be completed in the winter of 2023. Construction is slated to commence in 2024.

*EIR Addendum to be presented to the Board of Supervisor for acceptance on January 23, 2024.

Close window