The Green Streets Clean Water Plan has been developed to identify multi-benefit green streets opportunities within the village areas of the western draining watersheds in the unincorporated County. Green streets are projects that implement green infrastructure BMPs within the County’s road right-of-way to capture, slow, and filter stormwater. These BMPs are designed to treat runoff from impervious areas such as streets, sidewalks, and adjacent land areas. When integrated with complete streets and within development projects, they create additional urban greening and support walking, biking, and transit use, which in-turn supports economic, health, environmental, and community benefits.
How do Green Streets Improve Water Quality?
- When it rains, runoff collects along roads in ditches, gutters, and storm drains.
- This runoff caries pollutants that can impact our streams, rivers, reservoirs, beaches, shoreline, and ocean.
- During dry weather, the water we use throughout the day can have similar effects.
- Green Streets use natural processes, including filtration through plants and soil, to treat water runoff in an environmentally friendly way.
- Other runoff treatment systems are fully underground and can partner with surface systems to assist our infrastructure.
What is the Green Streets Clean Water Plan?
The County of San Diego Green Streets Clean Water Program evaluated
nearly 1,200 miles of roads in the unincorporated area, looking for
opportunities to use green street retrofits to support clean water in
local creeks, rivers, lakes, and ultimately the ocean.
The Green Streets Clean Water Plan identified the highest priority multi-benefit locations for green streets across 24 community planning areas. Local community benefits that were considered include supporting aquifer recharge, improving pedestrian safety, and enhancing green spaces.
Policy recommendations made are "paving the way" for future green street opportunities.
The Green Streets Clean Water Plan Includes:
- An introduction to green streets and how they can be used to improve our water quality and our communities.
- Evaluations of project feasibility and benefits to both water quality and communities.
- Blueprints for those interested in future green street projects.
Frequently Asked Questions:
1) Is there a list available of project areas currently under
consideration for green streets?
Priority drainage areas and candidate project sites are provided in the Green Streets Clean Water Plan. Information on projects sponsored by the Watershed Protection Program can be found on the County's Green Infrastructure page.
2) The Mapleview Green Street Project was described during the Green
Streets Clean Water Webinar. Is it one of the 30 projects included in
the Green Streets Clean Water Plan?
No, it is not one of the 30 projects listed in Green Streets Clean Water Plan. Construction of the Mapleview Green Street Project is is scheduled for the spring of 2022.
3) Will all medians be raised and landscaped?
The incorporation of raised medians on County road projects depends on a number of factors including road classification, traffic movement, and traffic safety. In most cases raised medians are not vegetated. The use of raised medians with vegetation will be considered on green street projects, but only when a substantial water quality benefit can be achieved. Specific project design will be presented to the community similar to any Capital Improvement Program project.
4) How do trees help treat stormwater runoff?
Tree root systems help the surrounding soil absorb more rainfall and stormwater runoff by reducing soil compaction. As storm water runoff percolates into the soil, natural processes can filter out pollutants.
5) How will vegetation be irrigated?
Irrigation requirements would depend on the type of vegetation proposed and availability of water. If irrigation is needed, it will be installed consistent with the County's Water-Efficient Landscape Design Manual. Specific project design will be presented to the community similar to any Capital Improvement Program project.
6) Will traffic calming mean reduced lanes? What if the community does
not like reduced lanes?
Traffic calming can be accomplished through a number of different measures without resorting to the reduction of traffic lanes. Any of the proposed traffic calming measures will be communicated to the community and presented to the local Community Planning Group.
7) Are Type IV (protected) bike lanes under consideration for the
Mapleview project or any of these other projects?
Type IV bike lanes are not included as part of the Mapleview Project. Fitting Type IV bike lanes into existing roadways can be challenging due to the limited space within the existing built environment and right-of-way. If a green street project is proposed in an area identified for Type IV bike lanes in the County's Active Transportation Plan, the bike lane opportunity will be considered along with other priorities for that specific project.
8) Will tree wells be designed so that the trees will not buckle
pavement as they mature?
The County's Green Streets Standard Drawings include design specifications for tree wells and biofiltration media. They include design features that direct roots downward, rather than horizontally, in an effort to avoid impacts to sidewalks and roadways. These design specifications provide sufficient volume for root establishment and runoff storage. Trees should be able to reach their natural heights.
9) Could this program create a vector control problem by allowing
standing or ponded water and thus breeding of mosquitos?
Projects will be designed to avoid the ponding of water. The County's Green Streets Standard Drawings, which will be used for this project, intentionally limit the depth of ponded water and require efficient drain times to avoid becoming a breeding environment. Projects with underdrains will provide a backup mechanism for collected runoff to exit the treatment systems to ensure that ponding will not occur.
10) How are these projects funded?
Green Infrastructure projects are primarily funded through the County general fund and supplemented with water quality grants.
11) What jobs will this program create? Are they long-term or for
There will be short-term construction jobs associated with these green street projects. The improvements and aesthetically pleasing features that these projects include could offer long-term job benefits as well, if they bring more visitors to the local community. Maintenance work on green street features will also be needed.
12) Who will maintain the landscaping?
There could be more than one entity involved in landscape maintenance. The County's Department of Public Works is responsible for ensuring that landscaping in the right-of-way is maintained, either through the use of County Road Crews or a landscape contractor.
13) Where will the funding come from to maintain the landscaping?
County general fund is currently identified as the funding source for green street projects. The County plans to use drought-tolerant, native, and non-invasive plant species in landscaped areas. These plants, once established, may be less costly to maintain and irrigate.
14) How will water supply concerns be considered for vegetated green
streets that require irrigation?
Vegetated green street projects will be landscaped using drought-tolerant, non-invasive vegetation, with a preference for native species. Such plants will require some supplemental water when first established, with the goal of transitioning away from irrigation over the long-term. Additionally, green street projects are intentionally sited and designed to receive runoff from roads, curbs/gutters, and sidewalks during both dry weather (from sources such as over-irrigation) and wet weather. This will further offset the demand for irrigation.
15) How will green street projects impact residential street
right-of-way frontages that a homeowner may have landscaped themselves?
While the majority of projects will be located outside of residential areas, the County recognizes that residents are invested in the condition of the right-of-way adjacent to their property, and understand that some right-of-way areas have been landscaped. If a project is planned in such a location, the County will take this into consideration during the design phase. In cases where prior landscaping necessitates removal, replacement landscaping would be designed to be aesthetically pleasing, pollinator friendly, etc.
16) Is proximity to schools being considered in the placement of green
Proximity to schools is one of many factors considered in the overall scoring of potential green street projects.