Permeable Interlocking Concrete Pavement
The U.S. Federal Highway Administration (FHWA) has published a TechBrief titled “Permeable Interlocking Concrete Pavement (PICP)”. This TechBrief presents an overview of PICP and its use. General information is provided on PICP composition with a summary of benefits, limitations and characteristics, along with important considerations such as hydrological design, structural design, construction, and maintenance. PICP consists of solid concrete paving units with joints that create openings in the pavement surface when assembled into a pattern. (The U.S. Environmental Protection Agency (EPA) has a fact sheet on PICP.)
The joints are filled with permeable aggregates that allow water to freely enter the surface. The permeable surface allows flow rates as high as 2,540 cm/hr (1,000 in/hr) (Borst 2010). The paving units are placed on a bedding layer of permeable aggregates which rests over a base and subbase of open-graded aggregates. The concrete pavers, bedding and base layers are typically restrained by a concrete curb in vehicular applications. The base and subbase store water and allow it to infiltrate into the soil subgrade. Perforated underdrains in the base or subbase are used to remove water that does not infiltrate within a given design period—typically 48 to 72 hours. Geosynthetics such as geotextiles, geogrids or geomembranes are applied to the subgrade depending on structural and hydrologic design objectives. Separation geotextiles are used on the sides of the base/subbase to prevent entrance of fines from adjacent soils. PICP may help achieve compliance with many national, provincial, state and local regulations as well as transportation agency design requirements for stormwater runoff control.