Urban soils | Soil Science

Terms: urban soils, structural cells, structural soils, suspended pavement
Urban soils are found in highly populated areas where they have been altered by human activities, including construction and building. Since it can also be used as an engineering medium, it’s often highly compacted to support roads and homes. This is in direct conflict with what trees need for growth.
Some engineered options have emerged:
Structural soils are a growing medium consisting of angular rock with a small amount of soil mixed in; depending on the recipe, there may also be additives like hydrogel. The rocks resist compaction but press against each other to support the aboveground load. They also have voids in between themselves, which is where the soil sits. Good irrigation and drainage is a must. Cornell’s CU Soil is an example of a structural soil.
Suspended pavement is pavement that is supported on a structure of columns/posts and beams. Since the structure is supporting the load, the soil can be natural & loose. These systems are engineered individually.
Structural cells are similar to suspended pavement but are modular units that can be put together to support a surface. The space within the units are filled with loose soil. A well known brand is Silva cells. They can also be used to create more stormwater retention areas on densely developed projects.
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