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• <br /> Functions of Bio-Retention <br /> The bio- retention area functions as a soil and plant -based filter filtration device that removes <br /> pollutants through a variety of physical, biological and chemical treatment processes. It <br /> consists of a ponding retention area, vegetated surface, `sandy loam' soil mix layer, an organic <br /> or mulch layer, a gravel layer and an underground drainage system. The runoff's velocity is <br /> retarded by distributing the runoff evenly over the surface of the planter bed. The runoff <br /> interacts with the vegetation as it passes over the surface of the planter it and with the soil <br /> medium and soil microbes as it passes through the soil and gravel layers. The filtered runoff is <br /> collected by perforated piping within the gravel layer and conveyed to the underground stone <br /> drain piping system that discharges to the offsite storm system. <br /> Inspection and Maintenance Requirements <br /> The areas require frequent landscaping maintenance, including measures to ensure that the area <br /> is functioning properly, that inlets are free of debris and perforated piping is Flowing freely as <br /> well as maintenance of the surface vegetation. Maintenance tasks may be performed by a <br /> qualified landscape contractor. <br /> 5/1/2012 <br /> 3 <br />