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Stormwater Tree Trench

A stormwater tree trench is a system of trees that are connected by an underground infiltration structure. On the surface, a stormwater tree trench looks just like a series of street tree pits. However, under the sidewalk, there is an engineered system to manage the incoming runoff. This system is composed of a trench dug along the sidewalk, lined with a permeable geotextile fabric, filled with stone or gravel, and topped off with soil and trees. Stormwater runoff flows through a special inlet (storm drain) leading to the stormwater tree trench. The runoff is stored in the empty spaces between the stones, watering the trees and slowly infiltrating through the bottom. If the capacity of this system is exceeded, stormwater runoff can bypass it entirely and flow into an existing street inlet.

Stormwater Tree Trench at West Mill Creek

Runoff from the street and sidewalk is diverted into a stormwater tree trench at the intersection of Ogden and Ramsey Streets in West Philadelphia through modified inlet structures. Trees are planted in pockets of soil within a continuous stone trench that stores stormwater until it can infiltrate. Porous pavers replaced the brick sidewalk over the trench and allow runoff from the sidewalk to infiltrate into the trench. The continuous trench also provides the tree roots with better access to air and water.



Ogden and Ramsey Street, Philadelphia, PA

Mill Creek - Parkside

Lead Agency

Philadelphia Water Department


Pennsylvania Horticultural Society
Pennsylvania Department of Environmental Protection
Philadelphia Department of Recreation