Factors to consider when using permeable pavements:
• Do not use permeable pavements where there will be very heavy silt loads from the proposed use (e.g. stockpiling sawdust or large recycling centres subject to heavy silt loads)
• It is possible to construct part of an area in impermeable materials that drain onto a permeable pavement. For example, car parking bays are often constructed using permeable paving and the access ways are impermeable construction
• Open graded permeable sub-base below the permeable pavement should not be used by construction traffic, as this will increase the likelihood of clogging
• The design of permeable pavements must take into account the overland flow routes of water when the design capacity is exceeded. Although exceedance will result in flooding of some areas of a site, the flows should be routed to prevent flooding of buildings for events that are well in exceedance of the capacity of the system. Further guidance is provided in CIRIA Report C 635 (CIRIA, 2006)