STRUCTURAL MEASURES: CONSTRUCTION, OPERATION, AND MAINTENANCE - Low Impact Development and Sustainable Stormwater Management - page 174

Restoration of Porous Pavements
Potholes in pervious pavement are extremely unlikely, although settling might
occur if a soft spot in the subgrade is not removed during construction. For
damaged areas of less than 50 square feet, a declivity could be patched by any
means suitable with standard pavement, with the loss of porosity of that area
being insignificant. The declivity can also be filled with pervious mix or paver
units. If an area greater than 50 square feet is in need of repair, approval of
the patch type must be sought from either the engineer or the owner. Under
no circumstance is the pavement surface ever to be seal-coated. Any required
repair of drainage structures should be done promptly to ensure continued proper
functioning of the system.
With minimal maintenance, pervious pavement can function effectively for
well over 20 years (the oldest system still in operation was installed in 1982 (see
Figure 4-5). However, in the event that maintenance of the pervious pavement
is neglected and it becomes clogged over time, the owner should vacuum the
lot until the original permeability is restored. (If the original permeability of the
lot cannot be restored, the pavement should be removed and replaced with a
new pervious mix or pervious units.) Recent research has shown that one of the
most effective ways of restoring pervious pavement is by applying a pressurized
dose of a nontoxic detergent cleaning solution, allowing adequate soak time, and
then vacuuming using a high-performance unit (e.g., Elgin Whirlwind, Allianz
Model 650). Once again, it is important to note that high-pressure washing may
drive contaminants farther into the pervious surface, even into the underlying
aggregate. It is therefore recommended that prior to vacuum sweeping, a low-
performance pressure washer be used to get the solution to break the surface
tension and reach into the pores.
Pervious pavement maintenance considerations can be summarized as follows:
• The surface should never be seal-coated.
• Inspect for pavement rutting or raveling on an annual basis (some minor
ruts may occur in pervious pavement from stationary wheel rotation).
• Damaged areas of less than 50 ft 2 can be patched with pervious or standard
pavement.
• Larger areas should be patched with an approved pervious pavement.
Cost of Porous Pavement
The majority of added cost of a pervious pavement or infiltration system lies in
the underlying stone bed, which is generally deeper than a conventional subbase
and lined with nonwoven geotextile. However, for new construction projects,
this additional cost is often offset by the significant reduction in the drainage
infrastructure required (i.e., inlets and pipes). Also, since pervious pavement
areas are often incorporated into the natural topography of a site, fewer earth-
work and/or deep excavations are generally involved. Perhaps most significantly,