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Sunday, May 30, 2010

Silva Cells - Aurora Phase II Is Top Project

Shoreline's Aurora Phase II Project is now the largest ever use in state of "Silva Cell" Deeproots System for tree planting. 

City of Shoreline Aurora Project Silva Cell Installation

The Silva Cell application allows a tree to achieve maximum root growth.
Photo credit - Google images

 The concept is designed to allow the street trees to thrive and let their roots expand without disrupting sidewalks or pavement. Street trees traditionally have a difficult time because of the conflicts that will result with adjacent paved areas.  This technique allows the trees to grow naturally, because of the surrounding gravel beds and pervious sidewalks, which are supported by the "cells".  It also combines stormwater runoff infiltration technology and water quality benefits. 

The City of Shoreline is undertaking a huge remodel on the second phase of the Aurora Project with additional state of the art technologies to better address stormwater issues. The Shoreline City Council approved the "Hybrid Plan" Phase II project unanimously in 2007, and one of the major factors in arriving at a consensus was inclusion of this suite of Stormwater Control techniques. The Silva Cell Deeproot System is just one of many technologies being utilized including natural stormwater treatments such as pervious pavements and filtration concepts.  The business community worked with the City to achieve working solutions to connect the highway to local businesses. The project is supported by grant funding from the State and Federal governments.

Providing Street Trees and landscaping was one of the goals of the project along with BRT(Bus Rapid Transit), safety and improved pedestrian facilities. Silva Cells are a great way to achieve this goal and allow the trees to prosper. That way they will hopefully avoid the fate of other street trees in our community recently.

Photo credit - Vicki Westberg

Former Shoreline Mayor Cindy Ryu, made a statement at a recent "Complete Streets" event hosted by Cascade Land Conservancy about the techniques Shoreline is deploying. 

In 2006, Shoreline  adopted a goal “to create an environmentally sustainable community” and in 2008 an award winning comprehensive Environmental Sustainability Strategy.  We have been incorporating elements of Complete Streets in our “environmental tool kit” for Capital Projects.   

What started out as a beautification and safety road project in the first mile of Aurora Avenue project was made even better for the 2nd and third miles of this State Highway because of our focus on environmental sustainability.

In addition to the great start of sidewalks for pedestrians, the completion of the adjacent Interurban trail for bikes,  and a dedicated Business Access Transit lane, it will be "complete" with natural drainage systems, pervious sidewalks and installation of Silva Cells to improve the quality of water being released into Lake Washington.  In fact, it is the largest project using the Silva Cell tree well technology in the State to give trees the room to grow to their potential.

From site -

Silva Cell

The Silva Cell system holds soil for tree growth and stormwater management in a structure strong enough to support paved surfaces. Growing trees in urban areas can reduce the heat island effect, replenishes oxygen, and connects us with the natural environment. Silva Cells support this by creating a space that holds ten cubic feet of soil, enough for tree roots and most utilities. With the proper drainage medium they can also manage stormwater runoff to reduce flooding and erosion. The 48” x 24” x 16” fiberglass and polypropylene cells have galvanized steel supports and, to provide additional space, can be stacked up to three cells high before the decking is attached. Silva Cell meets the American Association of State Highway and Transportation H-20 standards for highway loading, so it can be used under most paved surfaces, from parking lots to streetscapes. Though the company does not recommend these under roadways. For use with new trees only and may require root barrier.

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