What is the incremental thickness for soil media installation in bioretention?

What is the incremental thickness for soil media installation in bioretention?

• A. 6 inches
• B. 24 inches
• C. 12 inches
• D. 18 inches

Answer: (C)

Layering the soil media in bioretention cells is done in uniform lifts to control compaction and maintain pore space for infiltration. Placing media in consistent, moderate lifts prevents heavy equipment from compacting too aggressively and helps avoid dense, low-permeability layers that would slow or block infiltration. This approach also supports even drainage, healthy root growth, and proper function of the underdrain system. In practice, the standard lift thickness used for installing the media is twelve inches, which balances providing adequate rooting depth and filtration capacity with the need to achieve the correct compaction and drainage during placement. Smaller lifts risk under-building the media depth, while larger lifts increase the chance of over-compaction and hinder drainage.

Layering the soil media in bioretention cells is done in uniform lifts to control compaction and maintain pore space for infiltration. Placing media in consistent, moderate lifts prevents heavy equipment from compacting too aggressively and helps avoid dense, low-permeability layers that would slow or block infiltration. This approach also supports even drainage, healthy root growth, and proper function of the underdrain system. In practice, the standard lift thickness used for installing the media is twelve inches, which balances providing adequate rooting depth and filtration capacity with the need to achieve the correct compaction and drainage during placement. Smaller lifts risk under-building the media depth, while larger lifts increase the chance of over-compaction and hinder drainage.