cA new tree structural support system has been recently certified in the state of Washington to be functionally equivalent to bioretention in managing stormwater.

Efficiently managing stormwater runoff is critical in U.S. urban areas; not only to prevent the water from overwhelming sewer systems but also to capture the valuable resource to support urban trees and plants.

Cities in western Washington have recently implemented new tools in hopes of improving their stormwater management. They have been installing underground frames that allow large trees to have more soil access even if surrounded by concrete.

Developed by DeepRoot, these structural support systems are known as Silva Cells. The Washington State Department of Ecology found through extensive modeling that this new system can have as much impact as a bioretention facility.

"Because the soil within the cells can be built to bioretention soil standards, it was clear to us that it should be considered equivalent," said Doug Howie of the Washington State Department of Ecology.

Graham Ray, CEO of DeepRoot adds, "Many are installed in the Seattle metro area and in Renton and Tacoma, but now that we are certified by one of the nation's most influential state agencies, we hope people will realize just how effective a tool this is for absorbing water from storms."

Washington State has some of the highest standards and requirements for designation as a stormwater management solution. The approval means that contractors can use the product on project sites without seeking any additional approval.

The modeling by the state's Department of Ecology found that besides allowing for the bioretention of water, the cells also offer additional flow control benefits by capturing water with their canopies.