Tree box filters can be useful in sites where land is valuable and limited, such as along urban sidewalks. Installing tree box filters is helpful in incorporating isolated street trees into stormwater filtration devices. They can be installed in open or closed bottomed chambers. This allows them to be adjusted in different settings and conditions, such as a high pollution area and where the native soil is clay.
The design of the tree box filter needs to be specified to fit with its application. There are 6 main factors in their design

Site conditions

• Tree box filters should have an enclosed, non-permeable container in situations where infiltration is undesirable. Some of these situations include: clay soils, karst topography, high groundwater conditions, locations close to buildings, steep slopes, and contaminated sites and environments.
• In the case of “hot spots,” where chemical can be spilled, the underdrain system can be installed with an emergency shut-off valve to quickly close the discharge drain pipe, which contains the spill in the concrete container. With this system, it is easy to clean-up, remove, and replace the filter system.
• Tree box filters can also meet landscape requirements. Plants can be integrated into the landscape design. 

Urban retrofit conditions
Since the filter is contained in a concrete box and is completely sealed, it can be built in and around roadways, sidewalks, buildings and parking lots. Some considerations for the individual box locations, designs, and plants are:

• Drainage infrastructure,
• Topography,
• Site conditions,
• Utility locations,
• Water quality requirements,
• Aesthetics, and
• Landscaping requirements

Aesthetic considerations
Although topography and hydrology are used in planning the general placement of each structure, the overall site’s aesthetic should be integrated at first in the site plan to fit with the design and planting design.

Sediment Control
Tree box filters should not be installed prior to full site stabilization without adequate protection.  If a tree box filter is installed when there is active construction within the drainage area, the opening to the filter should be blocked off completely. 

Pretreatment
Tree box filters are designed to operate without clogging under normal operating and maintenance conditions. A relatively small “drainage area to filter size” will make tree box filters very effective and increasing their longevity.

Observation Well and Clean-out
Tree box filters systems come with an observation well that can be used for cleaning out and removing any blockages in the underdrain piping.

Sizing Guidelines
Tree box filters should be sized to optimize the filter surface area – drainage area relationship to filter most of the rainfall intensities in your area. The total tree box filter surface area will depend on the size of the drainage area and the amount of annual volume that you need to control.
A 2-year study at the University of Virginia tested flow characteristics of a manufactured tree box filter (Filterra). It concluded that the optimum filter surface area to contributing drainage area is 0.33% (36 sq. ft.) per ¼ acre of contributing impervious surface area. It also established the following pollutant removal rates:

* One 6’ x 6’ tree box filter per ¼ Acre is the optimum size for pollutant removal and cost effectiveness.