Traditionally pits are dug into the ground which give trees a volume of around 1m3 for roots, rather than the 20-40m3 that they require. This results in stunted growth or pavement heaving. Eventually the tree will die from lack of water or excess heat from the pavement.
Structural soils have been designed to provide street trees and other plants a suitable growing environment while at the same time being load bearing and able to support pavement or other engineered surfaces.
The structural support soil system is a 2 part system; with one part being the aggregate based structural soil, and the other part being the planting media in the immediate vicinity of the root ball.