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BMP T5.15: Permeable Pavements <br />Purpose and Pavement for vehicular and pedestrian travel occupies roughly twice the <br />Definition space of buildings. Stormwater from vehicular pavement can contain <br />significant levels of solids, heavy metals, and hydrocarbon pollutants. <br />Both pedestrian and vehicular pavements also contribute to increased <br />peak flow durations and associated physical habitat degradation of <br />streams and wetlands. Optimum management of stormwater quality and <br />quantity from paved surfaces is, therefore, critical for improving fresh <br />and marine water conditions in Puget Sound. <br />The general categories of permeable paving systems include: <br />• Porous hot or warm -mix asphalt pavement (see Figure 5.3.4) is a <br />flexible pavement similar to standard asphalt that uses a bituminous <br />binder to adhere aggregate together. However, the fine material (sand <br />and finer) is reduced or eliminated and, as' a result, voids form between <br />the aggregate in the pavement surface and allow water to infiltrate. <br />Pervious Portland cement concrete (see Figure 5.3.4) is a rigid <br />pavement similar to conventional concrete that uses a cementitious <br />material to bind aggregate together. However, the fine aggregate <br />(sand) component is reduced or eliminated in the gradation and, as a <br />result, voids form between the aggregate in the pavement surface and <br />allow water to infiltrate. <br />Volume V — Runoff Treatment BMPs — December 2014 <br />5-15 <br />