CITYWIDE GREEN STREETS PROJECT

What is a green street?

A green street is a natural stormwater management approach that uses plants and soil to slow, filter, and cleanses stormwater from streets. Traditional stormwater management directs runoff into pipes. A green street manages stormwater at its source, where rain falls.

Green streets protect water quality in rivers and streams by removing up to 90% of pollutants. They replenish groundwater supplies, absorb carbon, improve air quality and neighborhood aesthetics, and provide green connections between parks and open space. Vegetated curb extensions improve pedestrian and bicycle safety, and calm traffic.

Stormwater in Urban Areas

In rural areas, rain water is infiltrated into the ground. Water is then filtrated natural through the soil and recharges ground water. This natural cycle becomes more difficult as areas are being developed. Urban areas have low permeability for water to infiltrate, water instead travels through roofs, streets, into a storm drain system and then released into local creeks and oceans.
Runoff is contaminated with debris, sediment, automobile fluids, fertilizers and other pollutants. Streets are designed for stormwater to travel quickly into drains, there is no opportunity to clean out any pollutants before it enters a water body. Developed cities contribute high amounts of stormwater due to large paved surfaces.

Citywide Green Streets Project

This project will use green infrastructure to redesign five street locations within the City of Calabasas. The design will include storm-water capture for reuse or recharge of aquifers by adding bio-retention swales and basins, and increasing permeable surfaces. The implementation of this project will improve water quality by using different filtration systems to capture and treat storm water surface flows entering Calabasas’ water streams.

Along with treating surface flows, there will be the addition of trees along the roadways to reduce carbon dioxide emissions. The added bio-swales and planted trees will provide an aesthetic enhancement by providing visually appealing landscapes. The project will incorporate educational outreach signage which will help to educate the community on the man benefits of the venture. Green streets will also increase the safety of pedestrians and road users by slowing down vehicle speeds.

Existing Conditions

  • Low permeability increases flooding and does not allow for water filtration
  • Urban runoff picks up pollutants from roadways like metals, motor oil, and nutrients
  • Increased sediment from unpaved locations
  • Water damage on roadway due to poor water surface management

The primary objectives of Citywide Green Streets Project:

  • Improve water quality by removing urban runoff pollutants
  • Reduce urban runoff entering the City’s storm drain system
  • Increase air quality by planting trees along the roadways
  • Educating the community on the benefits of Green streets
  • Increased water surface management with permeable surfaces


Conceptual Designs


Conceptual Designs

 

 

Proposed Locations

1. Malibu Hills Road

The project proposes to construct bio-filtration medians with impermeable liner and an underdrain along the road. The medians will serve as a pretreatment BMP that will capture and treat surface flows. Treated flows will be discharged into downstream catch basins.

Multi-Benefit Description:
1) Water Quality: The project will improve water quality by filtering flows through bio-filtration soil media.
2) Aesthetic Enhancements: The proposed improvement will include visually appealing landscape for the community.
3) Community Outreach: The project incorporates educational outreach signage which will help to educate the community on the many benefits of the venture.

 

2. Calabasas Road (East)

The project proposes to remove the existing sidewalk and replace it with a permeable surface. The road will be designed to direct the surface flows into newly constructed bio-filtration medians in order to treat incoming water by removing pollutants. The treated flows will be discharged into downstream catch basins.

Multi-Benefit Description:
1) Water Quality:
2) Aesthetic Enhancements: The proposed improvement will include visually appealing landscape for the community.
3) Community Outreach: The project incorporates educational outreach signage which will help to educate the community on the many benefits of the venture.

 

3. Calabasas Road (West)

The project proposes to remove the existing sidewalk and replace it with a permeable surface. The road will be designed to direct the surface flows into the curb to be treated with bio-filtration soil media. The treated flows will be discharged into downstream catch basins.

Multi-Benefit Description:
1) Water Quality:
2) Aesthetic Enhancements: The proposed improvement will include visually appealing landscape for the community.
3) Community Outreach: The project incorporates educational outreach signage which will help to educate the community on the many benefits of the venture.

 

4. Las Virgenes Road

The project proposes to add a vegetated swale on the west side of the road. The vegetated slope will serve as a pretreatment BMP that will capture and treat surface flows. Treated flows will discharged into tree-well filters. The tree-well filters will serve as infiltration chambers that will hold and gradually infiltrates through the soil media. The remaining unpaved shoulder will be covered with permeable pavement to serve as parking for the residents of the area.

Multi-Benefit Description:
1) Water Quality: The project will improve water quality by filtering flows through the vegetated swale and bio-filtration soil media and by reducing sediment due to the unpaved shoulder.
2) Aesthetic Enhancements: The proposed improvement will include visually appealing landscape for the community.
3) Community Outreach: The project incorporates educational outreach signage which will help to educate the community on the many benefits of the venture.

 

5. Parkway Calabasas

The project proposes to remove the existing median and construct bio-filtration medians with impermeable liner and an underdrain along the road. The medians will serve as a pretreatment BMP that will capture and treat surface flows. Treated flows will be discharged into downstream catch basins.

Multi-Benefit Description:
1) Water Quality: The project will improve water quality by filtering flows through bio-filtration soil media.
2) Aesthetic Enhancements: The proposed improvement will include visually appealing landscape for the community.
3) Community Outreach: The project incorporates educational outreach signage which will help to educate the community on the many benefits of the venture.

 

For more information:

Los Angeles Low Impact Development Manual:
https://dpw.lacounty.gov/ldd/lib/fp/Hydrology/Low%20Impact%20Development%20Standards%20Manual.pdf

Stormwater Pollution Fast Facts:
https://dpw.lacounty.gov/prg/stormwater/page_30.cfm

Learn about Green Streets:
https://www.epa.gov/G3/learn-about-green-streets

 

City of Calabasas © 2017