TREE WELLS AND

THEIR BENEFIT TO WATERSHED PROTECTION

Trees contribute to the beauty of San Diego County, but also play a vital role in protecting the environment. Trees can provide shade, filter the air we breathe, reduce erosion, and help remove pollutants from stormwater. Tree wells are an example of an enhanced site design Best Management Practice (BMP) that can be used for development or redevelopment projects to reduce the amount of pollutants going to the watershed/MS4, while providing multiple other benefits for the user and environment.

From above, tree wells are able to intercept stormwater through their canopy. Tree species with a larger canopy tend to capture more stormwater. Then from the ground level, tree wells divert stormwater runoff to the soil immediately surrounding the tree. Generally, the areas around the Tree Well are sloped to allow water to naturally flow into the depressed planting area. The runoff that is collected in the tree well filters through the soil, removing pollutants. In this manner, tree wells reduce the volume of runoff entering the storm drain system and can prevent surface floods. Tree wells are often found adjacent to walkways, driveways, and parking areas to capture and treat stormwater flowing from these surfaces.

The design of tree wells also allows them to be utilized in urban settings to effectively treat stormwater where other landscape options are typically limited or absent. Proper species selection and tree well placement can minimize problems that tend to be caused by roots and regular tree growth.