03 December 2015

First Rains Show How Green Streets Protect Creeks and the Bay

December 3, 2015

Jim Scanlin
Clean Water Program
(510) 670-6548

Alameda County, CA—As rains finally bring long awaited moisture to the parched Bay Area, a new generation of landscape designs in Alameda County help protect water quality and prevent flooding. These attractive solutions maximize the amount of water absorbed into and filtered by the soil, instead of gushing straight into storm drains, causing flooding and pollution. Known as “green infrastructure,” these designs mimic drainage patterns of natural landscapes by using permeable pavement and depressions in the ground that help divert water away from roads and other impervious surfaces. As a result, less rain water ends up as runoff that washes motor oil and other pollutants off streets and carries them into storm drains and then directly into creeks, wetlands and the Bay.

first-rains-press-release-smGreen Infrastructure like this plant-filled curb extension on Adeline Street in Emeryville help capture, filter and absorb rainwater runoff.

“Green infrastructure is a simple yet highly effective approach to keeping our waterways clean while also replenishing ground water,” noted Clean Water Program Manager Jim Scanlin. “When rain water is allowed to absorb slowly into the ground, it is filtered naturally by plants and soil. This process converts polluted stormwater into a much-needed resource.”

Alameda County is required to put in place a certain number of green infrastructure projects as part of the Regional Municipal Stormwater Permit. However, the county has many more such projects than legally required—currently close to 30. Examples include:

Adeline Street, 47th to 40th, Emeryville – Curbs were extended with gently sloped planted areas that capture and filter rain water running off the street. As water is absorbed into the ground, some of the gas, oil, and heavy metals that wash from streets are filtered out, adhering to leaves and soil. The curb plantings also beautify the area and shorten street crossings, making them safer for pedestrians.

Stanley Blvd, Unincorporated Alameda County – A 4-foot wide infiltration trench was constructed along a 3-mile stretch of this high-volume arterial street, located between the city limits of Livermore and Pleasanton. The plant-filled trench slows the flow of water washing off the street and filters it as it absorbs into the ground. California native plants chosen for their beauty, low water use and resilience improve aesthetics and provide wildlife habitat.

Bay Street parking lot, Fremont – The impervious surface of the parking lot was replaced with porous asphalt that allows rain water to absorb into a gravel bed below the surface, from where it can gradually filter into the soil, rather than being diverted by storm drains.

For more examples of public green infrastructure in Alameda County, visit www.CleanWaterProgram.org/GreenStreets. To read how residents can install green infrastructure elements on their private properties, visit www.CleanWaterProgram.org/DetainTheRain.