Capital project
Former Sunnyside Nursery Detention Basin Project
Watershed Reference

About the Project

Sunnyside detention basin is one component of the San Anselmo Flood Risk Reduction (SAFRR) Project and the information on this page is specific to these components of the overall project. For information about the SAFRR project as a whole, such as timelines for public meetings or videos of past presentations, visit that page by clicking here.

The concept for the Sunnyside detention basin is to excavate a portion of this 7.7 acre parcel to construct a depression that water can be diverted into from the adjacent creek, thereby temporarily reducing the downstream flow. The site is located two miles upstream of Fairfax, along Fairfax Creek before White Hill. The basin will have some concrete components such as a diversion structure and spillway, but will otherwise contain a naturalistic and planted bottom with low profile vegetation and grassy side slopes.

Conceptual Rendering of Sunnyside Basin


Conceptual Section of Sunnyside Basin

At its meeting on July 12, 2016, the Board of Supervisors entered into an agreement with the owners of the former Sunnyside Nursery at 3000 Sir Francis Drake Blvd. to purchase the property. 

The District has been meeting with neighbors, cleaning up and maintaining the property while it develops plans and a Draft Environmental Impact Report (EIR) for the overall project.


Any project at the former Sunnyside Nursery would aim to provide multibenefits in addition to those related to the flood risk reduction goal; these include creek, habitat, and possible recreational enhancements. A community-based participatory planning and design process would be used to engage residents and stakeholders, seek their input, and provide a pathway for them to help shape the project prior to its implementation.

Visit the San Anselmo Flood Risk Reduction page for project status and future public meeting information.


Design phases


Presentation to the Baywood Canyon and Trestle Glen Homeowner's Associations

A series of neighborhood meetings were held in August 2016 to review a preliminary concept plan for the Sunnyside site and to answer questions about the conceptual basin design and how it would be expected to operate during a flood event. Presentation slides are below.

Background Documents

Examples of detention sites in other communities

Technical studies

Former Nursery Detention Basin Project Field Investigation Report

Former Nursery Detention Basin Project Geotechnical Report 

Purchase Agreement Information

Purchase agreement and board letter were presented to and approved by the Board of Supervisors of the Marin County Flood Control & Water Conservation District in July of 2016. 

Courtesy notifications 

Courtesy letters provided to neighbors of the former Sunnyside Nursery property:

  • Letter 1 June 17, 2016
  • Letter 2 July 14, 2016 

Implementing Agency & Partners

Marin County Flood Control & Water Conservation District is the implementing agency. 


The staff contact for the Marin County Flood Control & Water Conservation District is Liz Lewis, Planning Manager 415-473-7226).



If you are a person with a disability and require these documents in an alternate format (example: Braille, Large Print, Audiotape, CD-ROM), you may request an alternate format document by using the contact information below. If you require an accommodation (example: ASL Interpreter, reader, note taker) to participate in any county program, service or activity, you may request an accommodation by calling (415) 473-4381 (voice) / (415) 473-3232 (TTY) or by e-mail at not less than four work days in advance of the event.