Porous Concrete Sidewalks — How to Build Sidewalks, Not Stormwater Ponds

Building sidewalks typically triggers stormwater mitigation requirements. Sometimes the cost of creating the stormwater mitigation for a new sidewalk can exceed the cost of constructing the sidewalk. Using permeable pavements is one way to create sidewalks without triggering stormwater mitigation requirements. The City of Olympia, Washington has installed over 9,500 square yards or about three miles of porous concrete sidewalk to date, with more projects planned each year. We have experience with three different types of porous concrete materials over an eight-year period. Materials range from the regular "no-fines" porous concrete to a new form of 100 percent sand "all-fines" concrete. This paper presents the lessons learned and current state of porous sidewalk technology in Olympia. Our experience with different materials, design, construction, and maintenance is provided along with construction and operating costs.