Green Stormwater Infrastructure

The City of Palo Alto is subject to the requirements of the Municipal Regional Stormwater National Pollutant Discharge Elimination System Permit (MRP). A section of the MRP requires the City to develop and implement long-term Green Stormwater Infrastructure (GSI) Plans for the inclusion of GSI measures into storm drain infrastructure on public and (sometimes) private property, including streets, roads, parking lots, roofs, and other elements. 

The City’s GSI Plan is now complete! Please view the City’s Final Green Stormwater Infrastructure (GSI) Plan that was accepted by City Council on Monday May 13, 2019. 

What is Green Stormwater Infrastructure (GSI)?

“Green Stormwater Infrastructure” (GSI) uses vegetation, soils, and natural processes to manage stormwater runoff (Figure 1). Examples of GSI include landscape-based stormwater “biotreatment” using soil and plants ranging in size from grasses to trees; pervious paving systems (e.g., interlocking concrete pavers, porous asphalt, and pervious concrete); tree wells with suspended pavement systems; and other methods to capture and use stormwater as a resource. To see examples of GSI, view our "Green Streets Improve Communities" Utility Bill Insert.

GSI roadway projects, called “Green Streets,” provide many benefits: increased multi-modal travel and safety; clean water and air; climate change resilience and mitigation; placemaking and community cohesion; habitat and energy savings; and higher property values.  

A collage of stormwater infrastructure. From left to right: A plant-based "green" wall at Mitchell Park Community Center; a bio-retention basin in the Southgate neighborhood; a bio-retention basin at Lucie Stern Community Center; Matadero Pump Station
Figure 1. GSI Examples

Stormwater Permit Requirements for GSI

The GSI Plan must demonstrate the City’s long-term commitment to GSI implementation to help reduce pollutants of concern (e.g., mercury and PCBs) discharged to local waterways. The Plan must be completed and approved by the City Council by September 30, 2019.

 As part of the GSI planning process, the City Manager approved the required Green Stormwater Infrastructure Plan Framework, which serves as the outline document for the GSI Plan, on June 30, 2017.  The City’s Framework can be reviewed for an idea of what’s to come.

City of Palo Alto’s GSI Plan

The GSI Plan describes how the City will gradually integrate GSI features into its facilities, public right-of-ways, and urban landscape.

Where feasible, the City hopes to create a more resilient, sustainable system that may carry out one or more of the following functions:

  1. Reduces, slows and detains runoff by dispersing it to vegetated areas
  2. Promotes infiltration and evapotranspiration
  3. Collects runoff for non-potable uses
  4. Treats runoff using biotreatment and other GSI practices
  5. Helps reduce loads of pollutants of concern (POCs), particularly mercury, PCBs, trash and pesticides
  6. Incorporates landscaping features within areas that encourage more pedestrian and bicycle safety

Finally, the Plan will be coordinated with relevant State, regional and other City plans, such as the Comprehensive Plan, Transportation, Bicycle and Pedestrian, Parks, Urban Forestry, Sustainability, and Storm Drain Master Plans, to achieve multiple potential benefits to the community, including improved water and air quality, reduced street ponding, traffic calming, improved pedestrian and bicycle facilities, climate resiliency, improved wildlife habitat, and a more pleasant urban environment. 

A GSI Workgroup (made up of staff from various City Departments) was established to create a coordinated and Comprehensive Plan. These meetings are facilitated by Public Works’ Environmental Services staff, with support from a consultant team hired to help develop the GSI Plan. The Stormwater Oversight Committee, formed to review proposed expenditures funded by the City’s Stormwater Management Fee (which provides some GSI funding), will also be involved in plan development.

The City's 2019 timeline for developing the Plan is available below.

The City's 2019 timeline for developing the Plan. City Council acceptance is expected to be in June 2019.


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