What can raise property values, reduce flooding, improve groundwater recharge, eliminate an eyesore, and bring neighbors together? A Green Alley (Street) Project!
More specifically, the Avalon Green Alley Demonstration Project, which is one of Los Angeles’s most recent green infrastructure projects. Other such projects include:
- Glen Oaks Boulevard Green Street – Torrent Resources
- Broadway Neighborhood Greenway – Torrent Resources
- Elmer Avenue Paseo – Torrent Resources
- Sun Valley EDA – Torrent Resources
- Laurel Canyon Boulevard Green Street – Torrent Resources
- Woodman Avenue Green Street
- Riverdale Green Street
- Burbank Boulevard Street Widening
- Manchester Neighborhood Greenway
- North Hollywood Green Alley
Many other major American Cities have similar green alley (street) programs meant to beautify neighborhoods, minimize the impacts of the urban environment, improve local hydrology, and bring neighbors together around a common good. An important outcome of the Avalon Project was to have a replicable model that demonstrated a comprehensive approach to Green Alleys that could be implemented throughout Los Angeles. With this in mind, it was imperative to design transferable features that comply with City regulations and permitting.
The overall design concept for the Avalon Project was one of converting an alley once meant for automobiles to one that was pedestrian centered. In order to achieve this transformation, the design called for replacing asphalt paving with permeable pavers and colored concrete, installing solar powered lights, large amounts of pedestrian level vegetation and fruit trees, boulders and benches for seating, interpretive signage, and a number stormwater best management practices (BMPs) meant to capture stormwater, minimize flooding, and ultimately recharge groundwater.
The inclusion of robust stormwater BMPs in the Avalon Project design is in part due to the City of Los Angeles’ expanded interest in stormwater management over the lifetime of the project. The most visible stormwater BMP to be implemented consists of the removal and replacement of impervious asphalt with light-colored permeable pavers and concrete.
Stormwater draining from within the project watershed will be collected beneath the permeable paving and in catch basins placed throughout the project limits and routed to a series of flows to drywells, which will pre-treat stormwater and then infiltrate it into the vadose (unsaturated) zone beneath the project. When the Avalon Green Alley Project is complete, it will capture and infiltrate the first ¾” of rainfall, which is typically them most polluted runoff. With a 7.33 acre project watershed, this amounts to about 76,000 gallons of stormwater each time it rains, meaning up to two million gallons of stormwater could be captured and infiltrated each year, assuming average annual rainfall.