Green Alleys Initiative – Transforming Polluted Alleys into Vibrant, Water-Smart Green Space

Waterways

Exposure to air toxins

Self-sufficiency

Obesity

Local water

Resilient communities

Tree canopy cover

Walk/bike/transit score

South LA

County of Los Angeles

City of Los Angeles

There are 900 linear miles of alleys in Los Angeles, representing 2,400 acres of potential open space. One third of these alleys are located in South Los Angeles, and are often used for illegal dumping and are prone to flooding. South Los Angeles also lacks parks and green space, as well as safe access for pedestrians and bicyclists. The paved alleys create heat islands that will grow even hotter with climate change.

Building on the success of the Avalon Green Alley Network Demonstration Project, The Trust for Public Land is transforming two new alley networks in South Los Angeles – the Central-Jefferson Network and the Quincy Jones network. Over the coming year, The Trust for Public Land will design the alleys and create construction documents for the Central-Jefferson High and Quincy Jones Green Alley Networks and continue to support and expand community outreach and education about the Green Alley Initiative. Construction of the alleys will begin in early 2018.

Taking into consideration the results of community outreach, hydrology studies, and stormwater analysis, the following design goals have been established for the new networks:

o Implement stormwater BMPs that will capture and infiltrate runoff

o Improve community fitness by creating a fitness loop

o Increase bike and pedestrian safety through traffic calming measures

o Increase safety through planting low growing plants and installing light fixtures to increase visibility at night

o Create murals, mosaics, and decorative fencing in the alleys to create beautiful public space that reflects the community.

The new alley networks will improve climate resiliency and transform currently blighted alleys in a dense, severely underserved community, into community assets that provide the following environmental and public health benefits:

o Capture and filter millions of gallons of stormwater

o Improve air quality

o Reduce the heat-island effect

o Reduce greenhouse gas emissions

o Improve quality of life in South Los Angeles

o Access to beautiful, useable green spaces

o Safer routes for pedestrians and bicyclists

The Green Alleys Initiative will also impact water supply in our drought-stricken region. Los Angeles imports 89% of its water at tremendous environmental and financial cost and yet we channel almost all of our rainwater to the ocean, treating it as a liability instead of a resource. By implementing stormwater capture elements in the alleys, rainwater will be able to recharge local aquifers and increase our water supply. South Los Angeles is ideal for green infrastructure implementation because it is located over the Los Angeles Forebay, which is capable of storing large quantities of groundwater and allows percolation into deeper aquifers that replenish the groundwater basin. Ongoing monitoring of the stormwater captured by the alleys will provide valuable information that will be used to inform water and green infrastructure policy at the local, regional, and state level.

The Trust for Public Land and the Council for Watershed Health (CWH) will conduct pre- and post-implementation evaluation and monitoring to quantify green alley benefits including water quality and stormwater capture. These data will be submitted to the International Stormwater BMP Database to help increase knowledge on green infrastructure and urban stormwater management. The CWH will also analyze the effects of the proposed BMPs on water quality and water supply as well as document the operations and maintenance needs of the BMPs. Evaluation is planned for six months prior to construction and 12 months after construction is complete.

Data will also be collected and analyzed to determine the reduction in pollutants resulting from the installation of the permeable pavers and dry wells. Flow meters located directly upstream of the drywells will quantify the volume of water captured and infiltrated. Water samples will also be analyzed for fecal indicator bacteria, total suspended solids, metals and hardness.

The Trust for Public Land will also measure the project’s additional benefits, including increased pedestrian traffic, reduced bulky-item dumping, and community engagement. These impacts will be measured through pedestrian counts, dumping counts, neighborhood surveys and interviews with residents and students. These data will be used to record the multiple benefits of green alleys and support development of green alley networks in Los Angeles and across the country.

Money

Volunteers

Publicity/awareness

Network/relationship support