4.6.2 Design

Mix designs for permeable pavement systems are different from conventional pavement systems. For successful application of any permeable paving system the subsequent basic guidelines must be followed:

Adequate site analysis and appropriate site application

As with all LID BMPs, adequate site analysis and the selection of the proper practice and materials within the context of the physical setting and development needs are critical. Important considerations include:
  • Snow storage.
  • Snow removal.
  • Vehicle use.
  • Soil type and permeability.
  • Depth to groundwater.
  • Topography and the potential for sediment inputs to the permeable pavement.
  • Surrounding pollution generating land uses.
  • Surrounding vegetation.
  • Maintenance needs.

Correct design specifications

There are many design needs common to most permeable pavements and some unique aspects to each system. Industry associations can assist with design and specification guidance. Common and system-specific design needs are provided in detail later in this section. In brief, they include proper site preparation, correct aggregate base, pavement surface mix design, geotextile separation layer (if included), and under-drain design (if included). All are essential for adequate infiltration, storage, and release of storm flows as well as structural integrity. Construction specifications should stipulate that contractors on the job site hold certificates from industry programs on installing their systems. The pervious concrete and permeable interlocking concrete paver industry associations offer such education programs for contractors. Specifications should also include contractor experience with projects of similar size and scope.