What is bioretention and how does it work?

Bioretention soil mix, or Bio Soil, is an engineered soil that is designed to be placed in bioretention areas that capture, retain, and treat stormwater runoff.  These areas are typically placed beside impervious surfaces such as buildings, parking lots, or roads so the runoff can be directed into the cell.  Rip rap or concrete flumes help dissipate the velocity of the runoff and a thin mulch layer on top along with specific plants are on the surface of the cell on top of the bioretention soil mix.  The bioretention soil is designed to have a specific range of infiltration for the water to move through the soil.  The organic material and soil’s ability to update nutrients and other contaminants acts like a filter for the stormwater.  The water is allowed to remain in the cell for uptake by the plants, infiltrate into the groundwater, or filtered before discharge.  The soil must meet certain criteria for physical and chemical characteristics like pH, infiltration, texture, P-index, nutrients, soluble salts, organic matter, and more.