San Mateo County Stormwater Resource Plan

What is the San Mateo County Stormwater Resource Plan?

The San Mateo County Stormwater Resource Plan (SRP) is a comprehensive document that represents a significant transformation in watershed resource planning and stormwater runoff management. The SRP was developed by the City/County Association of Governments (C/CAG) of San Mateo County through its Countywide Water Pollution Prevention Program (Countywide Program), representing the twenty cities and towns and the County of San Mateo. The SRP was prepared through a collaborative effort with stakeholders and the public and tailored to the specific stormwater runoff issues in the region. The main goals of the SRP are to identify and prioritize opportunities to better utilize stormwater as a resource in San Mateo County through a detailed analysis of watershed processes, surface and groundwater resources, input from stakeholders and the public, and analysis of multiple benefits that can be achieved through strategically planned stormwater management projects. These project opportunities aim to capture and manage stormwater more sustainably, reduce flooding and pollution associated with runoff, improve biological functioning of plants, soils, and other natural infrastructure, and provide many community benefits, including cleaner air and water and enhanced aesthetic value of local streets and neighborhoods.

Through Senate Bill 985 (Pavley, 2014), SRPs are now required in order to compete for state grant funds from any voter-approved bond measures. The San Mateo County SRP is intended to fill that role for future stormwater management projects in the County.

Stormwater Resource Plan Approach

The San Mateo County SRP takes a watershed-based approach to prioritizing stormwater management projects. The screening and prioritization process is based primarily on critical watershed characteristics and processes, including land use, soil hydrology, land slope, and other relevant landscape features.  Opportunities to manage stormwater are prioritized through consideration of overall community benefits and the potential to co-locate stormwater capture projects with other currently planned and future capital improvement projects. Because ideal conditions for a suitable stormwater management project vary by type and size of project, projects were screened and prioritized into three overall categories: regional stormwater capture projects, green streets, and onsite stormwater management.  Regional projects capture runoff from large drainage areas and typically require larger parcels for siting infrastructure, green streets capture runoff from smaller drainages along roadway segments, and onsite stormwater management projects only capture and manage the runoff from a particular parcel or site. Twenty-two project concepts (see Appendix C) covering each of the three categories were developed in conjunction with the SRP to support potential grant applications by C/CAG’s member agencies.  In December 2017, the State Water Board awarded $1.2 million in Prop 1 stormwater grant funds to four of the 22 concepts, including green street and parking lot projects in the Cities of San Mateo (plus an additional green street project concept created separately) and Redwood City. Also leveraging efforts from the SRP, two regional-scale multi-benefit stormwater capture projects were advanced in the City of South San Francisco and Town of Atherton. Unfortunately, the project proposed in Atherton is not moving forward at this time due to challenges with finding a suitable location for the subsurface system that was supported by all stakeholders. The project at  Orange Memorial Park, however, is moving forward with construction in 2021. Both agencies have coordinated with Caltrans to receive project funding through cooperative implementation agreements.

The SRP is a collaborative model for addressing the opportunities and challenges in stormwater management in San Mateo County. The SRP includes GIS (geographic information system) data layers and locally planned projects from C/CAG’s member agencies.  C/CAG’s member agencies also provided important guidance and feedback while the plan was under development. As part of the public engagement component of the SRP, C/CAG held three public workshops in January 2017 to solicit public and stakeholder feedback on the SRP.  Public workshop presentation slides can be downloaded here.  Comments and responses are detailed in Appendix F.

Web Viewer

C/CAG created a web viewer to enable interested parties to view the results of the screening and prioritization process.  The viewer shows locations and relative rankings of regional stormwater capture, green street, and onsite stormwater management opportunities.  Instructions for using the viewer can be accessed here.

C/CAG  also created a pilot stormwater calculator to begin to evaluate the potential for individual projects in the County to capture and treat urban runoff.

Status of the Plan

The final draft of the San Mateo County SRP, which was developed in coordination with C/CAG’s member agencies and includes 22 detailed project concepts from across the County, was approved under Resolution 17-04 by the C/CAG Board of Directors February 9, 2017.  The SRP was also accepted by the Bay Area Integrated Regional Water Management Plan (IRWMP) Coordinating Committee on February 27, 2017 and was submitted to the State Water Board for review and reception of its letter of consistency in March 2017.

Stormwater Resource Plan and Appendices

Executive Summary

Main Report

APPENDIX A: Characterization of Imperviousness Study

APPENDIX B: Results of Quantitative Prioritization of Projects

APPENDIX C: Conceptual Design Fact Sheets

APPENDIX D: Bayfront and Vista Grande Canal Projects

APPENDIX E: Stakeholder List

APPENDIX F: Public Comment/Response Table

APPENDIX G: Stormwater Resource Plan Guidelines: Checklist and Self-Certification


For more information, please e-mail or 650-599-1433.

(plus an additional green street project concept created separately by the City of San Mateo)