The loose deep soils of the bioinfiltration basins absorb water and filter pollutants. Water quality is improved through filtration, sedimentation, and biological processes.

Water enters the basins via a diffuser system which spreads the water over a distribution rill into the basin. During heavy rain events, an equalization chamber allows water to flow from the upper to lower basin under an overpass at the entrance plaza. An overflow outlet distributes excess filtered water to the Japanese Garden pond.

Many soil profiles were designed to support various types of planting conditions within the project site ranging from planting and horticultural subsoils to bioinfiltration and tructural soils.

The bioinfiltration basins and street tree pits are surrounded by structural soils under plaza and sidewalk areas. The structural soils have more air space, expanding the volume of potential storm water capture and allowing for contiguous soil volumes supportive of tree root growth under paved areas. The structural soils provide stable support to paved areas without need for excessive soil compaction which is detrimental to healthy soil biology and sustaining plant life.