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Integrating Complete and Green Streets for Climate-Resilient Sustainable Streets

San Mateo County, CA, USA
City/County Association of Governments of San Mateo County
In Collaboration With
Green Infrastructure Leadership Exchange

Cost

Initial:
1.1 Million USD

Project Status

Operational since 2021

At a Glance

C/CAG prioritized planned Complete Streets projects to incorporate Green Streets elements, creating a countywide Sustainable Streets Master Plan to help equitably adapt the roadway network to climate change and clean stormwater runoff to meet municipal stormwater regulatory requirements.

Problem Addressed

C/CAG's climate change modeling indicates an increase in frequency and intensity of storm events in the future. Roadways, which serve as the primary surface conveyance for stormwater runoff, are likely to experience more frequent flooding due to storm drain systems, which are designed for certain size storm events based on historical rainfall records, being overwhelmed and unable to convey increased runoff volumes. These impacts may disproportionately affect downstream, vulnerable communities.

At the same time, Bay Area municipalities are required to implement green stormwater infrastructure to help reduce discharge of priority pollutants to San Francisco Bay under a regional municipal stormwater discharge permit. C/CAG, with significant grant funding from the California Department of Transportation (Caltrans), developed a countywide Sustainable Streets Master Plan. It prioritized already identified and planned active transportation and Complete Street investments for incorporation of green stormwater infrastructure to reduce runoff volumes and peak flow to help adapt to changing climate conditions, while simultaneously filtering out pollutants to help meet regulatory mandates.

Development of the Master Plan included an interwoven focus on equity, with prioritization criteria supporting projects in areas where 1) vehicle ownership is low and residents are more likely dependent upon active transportation or transit, 2) runoff volume is likely to increase the most due to climate change and lead to potential roadway flooding, 3) heat impacts are expected worsen due to climate change, 4) multiple environmental or social vulnerable or disadvantaged community indicators overlap, and 5) there is lower tree canopy coverage that could benefit from increased urban greening. Outreach efforts, including in-person and online events, were specifically targeted to reach disadvantaged communities. In addition to prioritizing Sustainable Street opportunities using already-planned or identified active transportation needs from the 21 jurisdictions, "new" opportunities at intersections within a 1/2 mile of schools or major transit stops on roadways with failing pavement were also identified and prioritized, further supporting communities dependent on active transportation or transit to get to school on roadways that have had historic under-investment in maintaining pavement conditions.

C/CAG used/is using Sustainable Streets to address this/these challenge(s).

Solution(s) Used

The Master Plan includes prioritized Sustainable Street projects throughout the county, climate modeling results showing how precipitation patterns are expected to change in the future, as well as how much Sustainable Streets can help mitigate these impacts.

The plan also outlines twelve project concepts showing different Sustainable Street typologies for locations throughout the county, model Sustainable Street policy documents for local agencies to consider to advance Sustainable Street implementation, and a web-based Green Infrastructure tracking tool that enables monitoring of progress over time on building climate resilience and meeting water quality improvement goals.

Outcomes

  1. Equity-focused prioritization of Sustainable Street project opportunities that integrate active transportation/Complete Street improvements with green stormwater infrastructure.
  2. Modeling of precipitation-based climate change impacts and quantification of the potential benefit of Sustainable Streets in adapting the roadway network to prevent flooding.
  3. Twelve project concepts of varying Sustainable Street typologies, from curb extension/intersection improvements to linear connectivity projects to complete streetscape reconstruction.
  4. Model Sustainable Street policy documents to enable municipalities to go beyond Complete Streets, including model Conditions of Approval for requiring Sustainable Streets of developers.
  5. Web-based green infrastructure tracking tool that allows documentation over time of progress toward climate resilience and water quality improvement goals.

Lessons Learned

  1. Sustainable Streets are an important way to cost-effectively and equitably build climate resilience and improve water quality while supporting active transportation and transit options.

Something Unique

This project was funded with a Caltrans Climate Adaptation Planning grant and shows the importance of integrating stormwater with transportation. Retrofitting the urban environment is too expensive to do multiple times for multiple purposes - all projects should be multi-benefit, and this marries active transportation, climate resilience, and water quality improvement in one project, with a focus on equity when prioritizing project opportunities and developing concepts.

Who Should Consider?

Local municipalities, stormwater utilities, transportation agencies, federal, state, regional, and local transportation and resource grant agencies

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