Permeable Pavement

Permeable Pavement
How does permeable pavement help manage stormwater?
Permeable pavements refer to paving materials that promote the absorption of rainfall and snowmelt. There are four main types of permeable pavements: porous concrete, porous asphalt, permeable grid pavers, and permeable pavers. See the table below for a detailed description of each paving system.

TYPES OF PERMEABLE PAVING SYSTEMS
Porous concrete
Porous concrete looks very similar to regular concrete. Porous concrete typically consists of specialty formulated mixtures of Portland cement, course aggregate and water that has been manufactured to have gaps through which water can flow into an infiltration bed of uniformly graded gravel.

Porous asphalt
Porous asphalt looks very similar to regular asphalt. Porous asphalt consisted of course aggregate bonded together by asphalt cement with sufficient gaps through which water can flow into an infiltration bed of uniformly graded gravel.

Permeable grid pavers
Permeable grid pavers are modular plastic pavers that fit together with funnel-like openings installed over infiltration bed of gravel. Depending on the site, grass or rock is used to fill in the funnel-like openings. Using plastic for the grids makes them very flexible and they can be used on uneven surfaces.

Permeable pavers
Permeable pavers are modular concrete pavers that fit together with funnel-like openings installed over infiltration bed of uniformly graded gravel. Depending on the site, grass or rock is used to fill in the funnel-like openings.

Each of the four types of permeable pavement systems is constructed with an underdrain and infiltration trench comprised of gravel underneath the paver, porous concrete, or porous asphalt. Rain that falls on the permeable pavement infiltrates into the gravel and then into the soil and/or groundwater below. Once the storage capacity of the infiltration trench has been reached, the underdrain will convey the water into the storm sewer system. By infiltrating the majority of the stormwater that falls onto the permeable pavement, the amount of water and pollution flowing into storm sewers or directly into streams is greatly reduced. Thus, permeable pavement helps maintain a more stable base flow to streams, reduces flood peaks, and reduces stream bank erosion.

Permeable pavement removes suspended solids through filtration. Dissolved pollutants such as nutrients and metals are removed and/or transformed as runoff infiltrates into the soil. Utilizing the Illinois EPA’s Estimating Pollutant Load Reductions for Nonpoint Source Pollution Control BMPs worksheets, the permeable pavement can remove approximately 75% of the total phosphorous, 90% of total suspended solids, and 100% of lead and zinc.

Where and how can Permeable Pavement be located?
Scale: Neighborhood, Lot
Applications: Retrofit, New, Preventative, Remedial, Ongoing/Maintenance, Parking lots, Streets, Driveways
Effectiveness: Runoff Rate Control, Runoff Volume Control, Sediment Control, Nutrient Control, Other Pollutant Control Additional Benefits of

Permeable Pavement
Permeable pavers provide much more than just stormwater management. They also:
  • Permeable pavements are just as stable as conventional methods and provide the same functionality of traditional concrete and asphalt. Snow melts faster on permeable pavements because of the improved drainage
  • Permeable pavements are also effective in reducing the “urban heat island” effect.
  • The use of vegetated pavers improves the aesthetic appeal of paved areas.
Maintenance
Permeable pavements should be inspected annually and after large storms to assure the pavements are still fully functioning. Permeable pavements should also be vacuumed periodically to remove any accumulated sediment and leaves. Vacuum-type street sweeping equipment is the most effect method of vacuuming permeable pavement systems. Snow and ice should be removed via scrapping and shoveling. Avoid the use of chemicals and sand on permeable pavement.through Illinois Environmental Protection Agency.

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