Permeable Pavement

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Permeable pavement is a type of pavement with a porous surface that is composed of concrete, open pore pavers or asphalt with an underlying stone reservoir. It allows water to run through it rather than accumulate on it or run off of it.  The water slowly infiltrates the soil below or is drained via a drain tile. The stone or gravel acts as a natural filter and clears the water of pollutants. It is important to note that one size does not fit all - there are many pros and cons for use of each type of permeable pavements

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  • Porous Asphalt and Pervious Concrete are like conventional asphalt and concrete but with less fine aggregate content leaving open spaces for water to pass through and soak into the ground. Porous asphalt and pervious concrete are the most suitable for large areas including residential driveways and parking lots.           More...

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  • Permeable paver systems have gaps between the pavers that allow water to pass. A layer of gravel under the paver system acts as a reservoir, holding rainwater while it soaks into the ground. Pervious paver systems are the most versatile type of permeable pavement and are suitable for residential driveways, patios, and parking lots.

  • Turf block systems are pavers with empty spaces filled with soil and planted. Turf block systems are suitable for residential driveways. 

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Summary of Permeable Pavement Design Requirements

These site and design requirements can help you decide if permeable pavement might be appropriate for your project.

  • Permeable pavement is allowed on surfaces with slopes no greater than 5 percent.

  • Underlying soils should have a minimum infiltration rate of 2 inches per hour.

  • There are no setback requirements for permeable pavement.  

  • There must be 5 feet between the high groundwater level and the excavated bottom.   

  • The subgrade next to structures should slope away from the structures.

  • Use a minimum of 6 inches of washed, crushed 2- to ¾-inch or No. 57 rock under concrete or asphalt.

  • Consult the Stormwater Management Manual regarding required edge restraints.

For best results, keep in mind the following construction considerations:

  • Protect the subgrade from over-compaction during excavation.  

  • Do not excavate or compact the native subgrade in wet conditions.  

  • Consider the sequence of construction activities to protect the subgrade from traffic. Protect the paving from construction traffic and sediment after installation.   

When to Call a Professional

Call a professional designer if you have more vehicle traffic than a residential driveway.

Also, if your soil infiltration rate is less than 2 inches per hour, you will need to hire a designer to help you. 

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Special Maintenance Considerations

  • Prevent Clogging of Pavement Surface with Sediment

    • Vacuum pavement twice per year

    • Maintain planted areas adjacent to pavement

    • Immediately clean any soil deposited on pavement

    • Do not allow construction staging, soil/mulch storage, etc. on unprotected pavement surface

    • Clean inlets draining to the subsurface bed twice per year

  • Snow/Ice Removal

    • Porous pavement systems generally perform better and require less treatment than standard pavements

    • Do not apply abrasives such as sand or cinders on or adjacent to porous pavement

    • Snow plowing is fine but should be done carefully (i.e. set the blade slightly higher than usual)

    • Salt application is acceptable, although more environmentally-benign deicers are preferable

  • Repairs

    • Surface should never be seal-coated

    • Damaged areas less than 50 sq. ft. can be patched with porous or standard asphalt

    • Larger areas should be patched with an approved porous asphalt

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