A tree well, or tree pit, consists of two main components: an underground structure and an above ground planting. The underground structure collects and filters stormwater using a bioretention system which typically consists of various layers of soil, mulch, and stone. These layers filter out pollutants contained in the stormwater such as oil, grease and salt. The treated stormwater can then infiltrate in the ground or discharge into the stormwater drainage system before entering local waterways. In addition to treating stormwater, tree wells add aesthetic appeal to roadways and neighborhoods, provide wildlife habitats, and provide shade to nearby buildings, thus reducing energy costs.
In 2011, two tree wells were installed at the Franklin downtown train station. Working in conjunction with the existing rain garden, the tree wells help collect and filter stormwater from the surrounding area.
Two additional tree wells were installed in 2013 on Island Road as part of a larger roadway improvement project.
Tree wells in downtown Franklin
Tree well design for Island Road Click image to enlarge
