About Green Infrastructure
Green infrastructure is a cost-effective, sustainable and environmentally friendly approach to stormwater management. Green infrastructure approaches such as bioretention infiltrate, evapotranspire, capture, detain and reuse stormwater to maintain, mimic, enhance or restore natural water processes. Green infrastructure reduces stress on traditional water drainage infrastructure such as storm sewers. The strategy in downtown Aiken is to maximize the bioretention capabilities of planted parkways in order to reduce the volume of and reduce pollutants in stormwater.
Bioretention is a natural water treatment system that utilizes landscaping and soils to treat stormwater by collecting it in shallow depressions and then filtering it through a planting soil media. Bioretention slows the flow of stormwater and allows it time to soak into soil while pollutants adhere, degrade, evaporate or are taken up by plants. Rain gardens and bioswales are types of bioretention areas.
A bioretention area consists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil and plants. Runoff passes first over or through a sand bed, which slows the runoff's velocity, distributes it evenly along the length of the ponding area, which consists of a surface organic layer and/or ground cover and the underlying planting soil. The ponding area is graded, its center depressed. Water is ponded to a depth of 6 inches and gradually infiltrates the bioretention area or is evapotranspired (evaporation into the air and absorption by plants).