|
Ponding Area - The ponding area provides surface storage for storm flows, particulate settling and the first stages of pollutant treatment within the cell.
Under-drain - The area above an under-drain pipe in a bioretention area provides detention ad pollutant filtering.
Filter Materials - Gravel blankets and filter fabrics buffer the under-drain system from sediment input and clogging.
Surface Overflow - Surface overflow can be provided by surface drains installed at the designed maximum ponding elevations that are connected to under-drain systems, or by overflow channels connected to downstream surface conveyance, such as bioretention swales and open space areas.
Hydraulic Restriction Layers - Adjacent roads, foundations or other infrastructure may require that infiltration pathways are restricted to prevent excessive hydrologic loading.
Plant Materials - Plant roots aid in the physical and chemical bonding of soil particles that is necessary to form stable aggregates, improve soil structure, and increase infiltration capacity.
Mulch Layer - Bioretention areas can be designed with or without a mulch layer; however, there are advantages to providing a mulch application or dense groundcover.
Soil - Proper soil specification, preparation and installation are the most critical factors for bioretention performance.
Compost - Organic soil amendment, suitable for landscaping and stormwater management, should be stable, mature compost derived from organic waste materials including yard debris, manures, bio-solids, wood wastes or other organic materials that meet the intent of the organic soil amendment specification.
|
