Green stormwater infrastructure (GSI) is infrastructure that uses vegetation, soils, and natural processes to manage rainwater and improve water quality. Similar to Low Impact Development (LID) measures, GSI also includes landscape-based stormwater treatment systems that uses soil and plants, pervious paving systems, rainwater harvesting systems, and other methods to capture and treat stormwater.
Common types of GSI include:
Stormwater Tree Well Filters
County’s GSI Commitment
On September 10, 2019, the County’s Board of Supervisors adopted the County's GSI Plan, which provides a roadmap for how the County will gradually transform traditional storm drainage systems from "gray" to "green" by incorporating GSI into projects in the public right-of-way and County-owned properties. The GSI Plan guides the process of identification, prioritization, tracking, and reporting projects. GSI will provide multiple benefits to the community, including improved water and air quality, reduced flooding, increased water supply, traffic calming, safer pedestrian and bicycle facilities, climate resiliency, improved wildlife habitat, a more sustainable urban environment, and help reduce loads of pollutants of concern (POCs), particularly mercury and polychlorinated biphenyls (PCBs), conveyed through stormwater into our local waterways, flowing from creeks out into the San Francisco and Monterey bays. PCBs and mercury were commonly used in industrial and electrical applications, building materials, and household items. These legacy pollutants are carried through stormwater and toxic levels can build up in fish and shellfish in the bay.