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14-2 <br />is removal from stormwater of potential pollutants adsorbed on <br />orabsorbed into suspended solids carried by stormwater. For cort~parison <br />purposes, schematics of a SB, a retention facility, and a detention <br />facility are presented in Figure 14.1. The terms "detention facility" <br />and "retention facility" are defined in Unit 3. <br />The terms "settling efficiency", "trap efficiency", and similar terms, <br />any one of which may be used in association with SB, have varied and <br />inconsistent meanings and interpretations in errosion-sedimentation <br />literature. Malcom and New (1975) draw a useful distinction between <br />these terms. They define settling efficiency as the fraction of <br />particles of a prescribed size trapped in a SB under design conditions <br />at peak out-flow. <br />Trap efficiency is defined by Malcom and New as the fraction of all <br />material removed by the SB under a variety of flow conditions and over <br />an extended period of time. Trap efficiency is expected to <br />significantly exceed settling efficiency because most runroff events <br />will be less severe than the design events. The concepts supporting the <br />terms "settling efficiency" and 'trap efficiency" could also be used <br />with respect to pollutants other than suspended solids. <br />Traditionally, SB have been used as part of errosion and sedimention <br />control systems in agricultural areas. Recently, as water uuality <br />