Green Infrastructure Resources
Municipal Regional Stormwater Permit Provision C.3.j. requires most Bay Area municipalities to complete and implement a Green Infrastructure Plan for the inclusion of Low Impact Development drainage design into storm drain infrastructure.
Each Green Infrastructure Plan will describe how, over the long term, the municipality will shift their streets, roads, storm drains, parking lots, and building roofs from conventional “gray” storm drain infrastructure—where runoff flows directly into storm drains and then to creeks and the Bay/Delta—to a more resilient, sustainable system that slows runoff by dispersing it to vegetated areas, promotes infiltration, and uses bioretention to clean runoff. The Plan will also describe how implementing Green Infrastructure will help meet load reduction targets for mercury and PCBs entering the Bay/Delta.
The municipalities’ Green Infrastructure Plans must be submitted to the San Francisco Bay Regional Water Quality Control Board by September 30, 2019. Each municipality has adopted a framework for completing their Plan by that date, including tasks and timeframes.
Required Green Infrastructure Plan elements include:
- Targets for the amount of impervious surface to be retrofitted by 2020, 2030, and 2040
- Prioritized projects and areas for potential projects for implementation
- Process for tracking and mapping completed projects
- Updates to planning documents (General Plans, Storm Drain Master Plans, Complete Streets Plans, etc.)
- Design guidelines
- Standard specifications and details
- Evaluation of funding options
- Policies and ordinances needed to implement
- Outreach and education
Municipalities must also review their current infrastructure projects, identify and prioritize where Green Infrastructure can be included as part of these projects (“no missed opportunities”), and include a workplan for completing prioritized projects.
Green Infrastructure Plan Preparation
The Contra Costa Clean Water Program is assisting Contra Costa municipalities with their Green Infrastructure planning. That assistance has included the following:
- Green Infrastructure Planning and Implementation Workshop, September 26, 2018
- Green Infrastructure Plan Template (2 MB .docx, April 2018)
- Green Infrastructure Planning Tasks, Roles, and Timeframes (100 KB .pdf, updated June 2018)
- Presentation Template: Developing a Green Infrastructure Plan for… (7 MB .pptx, December 2016)
Green Infrastructure Project Planning and Design
Here are some useful guidance manuals, design examples, and engineering details:
- Contra Costa Stormwater C.3 Guidebook
- San Mateo County Sustainable Green Streets and Parking Lots Design Guidebook
- National Association of City Transportation Officials (NACTO) Urban Street Stormwater Guide
- San Francisco Stormwater Management Requirements and Design Guidelines
- San Francisco PUC Stormwater Management Requirements and Design Guidelines Appendix B: Green Infrastructure Typical Details
- Green Infrastructure for Southwestern Neighborhoods (Tucson)
- Central Coast Low Impact Development Institute Bioretention Standard Details and Specifications
- Central Coast LIDI Complete Street/Green Street Checklist
CCCWP’s outreach efforts to promote Green Infrastructure have included the following:
- Presentation to the California Stormwater Quality Association (CASQA) Quarterly Meeting, May 10, 2018
- Presentation to Contra Costa Planning Directors (23 MB .pptx) at the Contra Costa Transportation Authority, May 10, 2018
- Presentation on Green Infrastructure Planning as part of CCCWP’s April 24, 2018 C.3 Workshop for Municipal Staff and Land Development Professionals
- Presentation to the East Bay Municipal Engineers, November 9, 2016
In April 2018, BASMAA published a Roadmap of Funding Solutions for Sustainable Streets. Funded by a USEPA grant and managed by the San Francisco Estuary Partnership, the roadmap includes specific actions designed to improve the availability of funding for Green Infrastructure Projects in the Bay Area and statewide.
Some Frequently Asked Questions about Green Infrastructure
What are the types of Green Infrastructure facilities, and where will these facilities be located?
“Green Infrastructure” includes facilities built on private land, often as a condition of approval for development or redevelopment, as well as retrofits to public parking lots and streets. Most public retrofit Green Infrastructure facilities will be bioretention facilities like those meeting the criteria in CCCWP’s Stormwater C.3 Guidebook.
Public Green Infrastructure facilities can be incorporated into street improvements, including bump-outs, curb extensions and other “complete streets” features installed to calm traffic and improve pedestrian safety.
What are the benefits and costs of Green Infrastructure?
In dry weather, Green Infrastructure stops spills, dumping, and non-stormwater flows from reaching creeks and the Bay/Delta. During runoff events, stormwater is filtered through a mix of sand and compost, removing most pollutants. The sand/compost “soil” is a living system, where insects, bacteria, and worms process fine particulates and incorporate them into the soil. Maintenance costs are low compared to mechanical treatment systems. Green Infrastructure has additional benefits: It enhances the quality of urban streetscapes, improves local air quality, mitigates the “heat island” effect, and adds some natural habitat to the urban setting. Larger bioretention facilities can double as parks and playgrounds. Green Infrastructure retrofit costs vary widely, depending on facility size and location, and depending on the extent and depth of curbs and walls required to protect adjacent pavement and structures. Rough estimates are around $2 to $5 per square foot of impervious area that is tributary to a Green Infrastructure facility.
How will Green Infrastructure projects be funded?
Green Infrastructure can be built most cost-effectively when it is incorporated into a street reconstruction or streetscape project, or other project where a street or site is being regraded for a new use. Some Green Infrastructure may be funded as part of project requirements. If the availability of funding can be timed correctly, there are various state and Federal grant programs to fund Green Infrastructure, and there are sometimes offset/mitigation funds available from public and private entities.
Can Green Infrastructure work where soils won’t infiltrate?
Most Bay Area soils infiltrate slowly—but fast enough to allow bioretention facilities to infiltrate 40% or more of total runoff over the course of a year. The remaining treated runoff is captured in perforated-pipe underdrains and conveyed to the storm drain system.
Will Green Infrastructure protect streams and reduce flood risk?
Bioretention facilities can reduce peak flows from small-to-moderate storms and make flows less “flashy.” The overall result is to reduce the frequency of small-storm flooding. Flood damages from larger, more rare storms typically affect structures in locations that have historically flooded (even before upstream watersheds were developed). Green Infrastructure will not substantially mitigate that risk.
What about operation and maintenance? How frequently must Green Infrastructure facilities be replaced?
Operation and maintenance costs tend to be in the same range, per unit area of bioretention facility, as maintenance for other landscaping maintained to a similar standard. Design guidance for bioretention calls for drip irrigation and “smart” controllers, with native, water-efficient plants that won’t require fertilizers or pesticides. Soils are intended to be self-sustaining. Structural elements (concrete curbs, walls, and overflow structures) have replacement cycles consistent with their use in “grey” infrastructure.
Will bioretention facilities eventually concentrate enough pollutants to require abatement?
No. Stormwater pollutants including PCBs and heavy metals are associated with dust and grime—fine sediment—that washes off during rainstorms. The fine sediment itself is not generally hazardous; however, unless removed, these sediments and their associated pollutants are transported to the Bay/Delta, where they enter the aquatic food chain. PCBs, mercury, and some other pollutants may then bioaccumulate and reach levels that could impact the health of aquatic organisms and could also affect human health when fish are consumed. When these same sediments are washed into bioretention facilities, they are trapped in the surface mulch and soils, adhere to soil particles, and are integrated into the soils through natural processes. Available evidence shows there may be a slight increase in background pollutant levels (particularly near inlets), but in any event, pollutant concentrations in bioretention facilities can be expected to be less than what is found in gutters and roadside dirt.
Will Green Infrastructure really make a difference?
Green Infrastructure facilities provide immediate, localized benefits at the location where installed. These benefits include protection against spills and dumping, improved runoff quality, and improvements to urban livability. It may take decades to implement “enough” Green Infrastructure to substantially address water quality problems (principally PCBs and mercury) in the San Francisco Bay/Delta. This is why the municipalities’ Green Infrastructure Plans will have a time horizon to 2040 and beyond.