Capital project
Phoenix Lake IRWM Retrofit
Watershed Reference

Proposal To Migrate Project Funding to Corte Madera Creek Flood Risk Management Project - Phase 1

Phoenix Lake project funding which includes a $7,661,000 state grant is currently being migrated to another project. The migrated project proposed is the Corte Madera Creek Flood Risk Management Project - Phase 1, and a link to this project is available be clicking here.

About the Original Phoenix Lake IRWM Retrofit Project

Phoenix Lake is currently owned and operated as a water supply reservoir by the Marin Municipal Water District (MMWD) and is open to the public for hiking, mountain biking, fishing, and other recreational uses. The Phoenix Lake Integrated Regional Watershed Management (IRWM) Retrofit project would modify the reservoir to allow it to serve as a detention basin, thereby reducing downstream flood risk in lower Ross Valley resultin from creek overflow during storms. Other related benefits include improved water quality in Phoenix Lake and Ross Creek, opportunities for increased water supply, and new recreational amenities. Based on the many benefits provided, the project was awarded a Department of Water Resources Proposition 1E grant in the amount of $7,661,000 in 2011. The total project cost at the time of the grant award was estimated to be $19,691,150. 

Status & Next Steps

The project is currently in the feasibility assessment phase. The Marin County Flood Control & Water Resources District (MCFCWRD) and MMWD are working together to evaluate the feasibility of possible improvement necessary to have Phoenix Lake serve as a detention basin. Studies currently in preparation include:

  • A study to collect soil samples from the earthen dam and determine what improvements to the dam might be needed.
  • A study to determine if the existing spillway and/or outlet pipe would need to be enlarged.
  • A study to examine how its use as a detention basin might affect its use as a water supply reservoir.
  • A study to measure the water quality in Ross Creek below Phoenix Lake.
  • A study to evaluate the existing ecosystem in Ross Creek below Phoenix Lake.
  • A study to propose operation procedures (called a Coordinated Operations Plan) to operate Phoenix Lake as both a detention basin and a water supply reservoir.

After the draft studies are complete to the satisfaction of both MCFCWRD and MMWD, the applicable studies will be reviewed by the California Division of Safety of Dams (DSOD). After any review comments by DSOD are addressed, the studies will be reviewed by the public and approved by MCFCWRD and MMWD.

After approval of the feasibility studies, the project will be reviewed according to the California Environmental Quality Act (CEQA). The CEQA review process includes review by both the public and applicable regulatory agencies.

Preliminary Schedule (pending approvals & funding)

Feasibility Assessment 6-9 months remaining as of 6/1/16
Environmental Review 12-18 months
Selection of Preferred Alternative 1-3 months
Design Development & Final Design 18-24 months
Construction 18-24 months
Total Duration Remaining as of 6/1/16 4 1/2 to 6 1/2 Years


View of Phoenix Lake
View of Phoenix Lake

Upcoming Meetings

None at this time.

Past Public Meetings

May 16, 2017: an update was provided as part of a presentation made by District staff during the Advisory Board meeting. The presentation is available below.

April 14, 2016: an update on the preparation of the feasibility studies was presented to the Ross Town Council.

Background Documents

Documents in bold are located below.

Some of these documents and concept plans may be outdated and superseded. Please contact the project manager to confirm the most current plans for this project.

  • Feasibility studies are currently being prepared and will be shared with the public for review and comment prior to being finalized.
  • 2011 Phoenix Lake DWR Proposition 1E IRWM Retrofit Application - All sections below submitted to CA Department of Water Resources for Prop 1E Stormwater Flood Management Grant - submitted April 15, 2011, Awarded December 21, 2011
  • These documents are below: Cover; Authorization and Eligibility Requirements; Bay Area Irwm Adoption of the Project; Work Plan;Budget; Schedule; Monitoring, Assessment, and Performance Measures; Economic Analysis - Flood Control Component; Economic Analysis - Water Supply Component; Economic Analysis - Water Quality Component; Costs and Benefits Summary; Program Preferences of Prop 1E Grant Program Compliance; AB 1420 Water Meter Compliance Information; Marin County Stormwater Resources Plan; Printed Copy of Online Entry From with Input Data

  • 2011 Technical Memorandum No. 2 on Detention Basins, Capital Improvement Plan Study. The Phoenix Lake Project plan view is shown on page 15 of 24. Pertinent attachments to Technical Memo No. 2 (19.1MB) relating to the Phoenix Lake Project are linked below for convenience:
    • Attachment B to Technical Memo No. 2 – Operations Plan of Ross Valley Detention Basins
    • Attachment C to Technical Memo No. 2 – Hydrologic Study of Re-0perating Phoenix Lake for Flood Detention and Water Supply
    • Attachment D (12.1MB) to Technical Memo No. 2 – Geotechnical Evaluation of Phoenix Lake
  • Memorandum of Understanding between MMWD and MCFCWCD
  • Preliminary Geotechnical Report - Miller Pacific Inc. - Included in Application for Prop 1E Grant
  • Project Map 1 - Facilities

  • Project Map 2 - Monitoring

Cost & Funding

The project is preliminarily estimated to cost $19.7 million (per the 2012 Department of Water Resources Proposition 1E grant application). Further development of the project details and project feasibility studies may result in increased estimated cost. Funding sources include the Ross Valley Flood Control Zone 9 Storm Drainage Fee, Department of Water Resources Proposition 1E grant, and other potential grant funding sources. 

Implementing Agency & Partners

Marin County Flood Control & Water Conservation District is the implementing agency in cooperation with the Marin Municipal Water District. 


The project manager for the Marin County Flood Control & Water Conservation District is Russ Eberwein, P.E., Senior Civil Engineer (