THE PROJECT - Visionary architects and designers in 2001 created what has proven to be a hyper-successful approach to changing the conventional way in which stormwater runoff is handled in urban developed areas. The project called Street Edge Alternatives, also known as SEA Streets has, after years of post-development evaluation, been determined to have decreased the volume of stormwater leaving the streets by 99%. The project designers accomplished this by reducing the traditionally impervious street surfaces of this north Seattle Washington residential area by a mere 11%.
This 11% of surface area was replaced instead with surface detention swales and adding more than 100 evergreen trees and more than 1000 shrubs. This reduction obviously resulted in a loss of street width and of course vehicle parking, which in and of itself dramatically increases the esthetic’s and overall appeal of the neighborhood. Areas of angle parking were added to replace the lost traditional parking spaces.
The diagram below provides an overview of the design.
This aerial photo below shows the design of the end project
This photo below shows the street view of the project
THE DESIGN – Prior to this redesign, the street was covered with pavement and compacted gravel that water could not permeate. The Natural Drainage System (NDS) that was utilized more closely simulates the earth’s natural ability to absorb and defuse rain water in shallow depressions, modified soil compositions, and most importantly plants. In addition, the sculpturing of the landscape attracted and pulled the water both from the paved streets as well as away from the homes.
THE IMPACT – So exactly what does this 99% reduction of street surface mean? The NDS design significantly reduced pollutants normally found in stormwater runoff such as oil, grease, automotive fuel, heavy metals, fertilizers, and other sediments from entering municipal storm systems and ultimately creeks, rivers, and lakes. This reduction also protects wild and water life. But the impact does not stop there. These reductions also lessen the costs associated with maintaining urban street and sewer infrastructures, increases property values by reducing the issues of water damage to homes, their foundations, and crawlspaces. Moreover, this project nearly eliminated maintenance cost for the green space by using the correct types and species of plants that are native to the areas in which they are planted.
We can make a difference - work toward bringing an NDS design to your neighborhood .
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