Tree Box Filter
About the Tree Box Filter
General Information Performance Data Water Quality Treatment Process Design

Unlike many other forms of urban landscaping, tree filters are not isolated behind curbs and deprived of water and nutrients from runoff. Instead, they receive runoff through breaks in the curbing, and demonstrate strong water quality treatment.

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About the Tree Box Filter

Tree box filters are mini bioretention systems that combine the versatility of manufactured devices with the water quality treatment of vegetated systems. They serve as attractive landscaping and drainage catchbasins. Unlike many other forms of urban landscaping, they are not isolated behind curbs and deprived of water and nutrients in runoff. Their water quality treatment performance is high, often equivalent to other bioretention systems, particularly when well distributed throughout a site.

Where to Use It

Tree box filters can be used throughout the United States, and are especially useful in settings where available space is at a premium. They can be installed in open- or closed-bottomed chambers where infiltration is undesirable or not possible, such as clay soils, sites with high groundwater, and areas with highly contaminated runoff.

Tree box filters are often installed along urban sidewalks, but they are highly adaptable and can be used in most development scenarios. In urban areas, tree filters can be used in the design of an integrated street landscape—a choice that transforms isolated street trees into stormwater filtration devices. They also can be used in designs that seek to convert entire non-functional streetscapes into large stormwater or combined sewer flow filtration systems.


These systems are a relatively recent innovation that is growing in usage, especially in urban areas. The cost to install a tree box filter to replace a catchbasin is $2,500. This does not include maintenance. UNHSC observations thus far reinforce stormwater manual assessments that maintenance requirements for these systems are generally minimal.

In general, tree box filters are sized and spaced much like catchbasin inlets, and design variations for these systems are abundant. The system evaluated at UNHSC was designed by center researchers. A similar patented design made by AmeriCast, the Filterra, is also available. Contact the UNHSC for more information about the design of the tree box filter.