Permeable Pavements for Roadway Shoulders

With an increased interest in low impact design and green infrastructure incentives, permeable pavements are becoming increasingly popular as an alternative pavement solution to minimize stormwater runoff and to improve water quality. Traditional shoulders are designed to provide a safety zone for emergency pull offs, provide a traffic lane during rehabilitation and maintenance operations, provide lateral support for the mainline pavement as well as providing a travel lane for other modes of transportation including buses, bicycles, etc. A permeable pavement shoulder system would provide all of these features as well as stormwater management benefits. The system would be designed such that surface water would flow across the pavement into the permeable shoulder into a stone reservoir. This stone reservoir would then temporarily store and treat the runoff The stored water would then either infiltrate into the subgrade soils or be discharged to other stormwater outlet systems. Highway shoulder applications provide a unique set of considerations that need to be evaluated and properly designed for prior to constructing permeable shoulders. The design of permeable pavement shoulders requires a balance between providing a structurally sufficient pavement to withstand traffic loading as well as achieving the stormwater management/ hydrologic design goals. Construction techniques and proper maintenance of the permeable shoulders are critical to the success and the longevity of the permeable pavement shoulders. Permeable pavements are not suitable for every shoulder application, however, with the proper design, construction and maintenance, they provide a low impact and green alternative that may be considered. This paper outlines permeable shoulder feasibility decision criteria along with design, construction and maintenance details for the successful use of permeable roadway shoulders.