Traditionally, paved surfaces are not porous, but instead shed water off onto the land or into sub surface drainage pipes as a liability (See Figure 3). Again, history reveals examples of old and new technologies that replicate natural patterns for infiltration (See Figure 4). Porous pavement and bio-infiltration swales can do much to infiltrate precipitation where it falls on paved areas. Porous pavement allows precipitation to pass through the pavement, through a porous sub-grade, and into porous soils below. A bio-infiltration swale accepts water that flows across a paved surface, cleanses it and passes into the sub-grade. There are other approaches one might take, but between these two tools, the surge of water from paved surfaces can be greatly reduced.