After installation of a permeable paver, maintenance is relatively minimal but absolutely
necessary to ensure the long lifetime of the system. Grass pavers will require the normal watering
and mowing maintenance of any turf system. Porous concrete and interlocking concrete paving blocks
require that the surface be kept clean of organic materials (leaves, for example), and periodic
vacuuming and low-pressure washing should be used to clear out voids and extend the paver’s
functional life. Conventional street sweepers should be used with vacuums, brushes and water
ideally four (4) times a year, but the actual required frequency will be determined by local
conditions. With the interlocking system, additional aggregate fill material may also need to be
added after cleaning.
With all of these systems, snow removal operations should be carefully considered, and the use of
sand or ash should be avoided as it may cause clogging of the pavement. Plowing requirements for
grass or gravel pavers are similar to those of any other unpaved road; in general, the blade must
be lifted to clear the grass or gravel surface. A mall in Connecticut with grass paver parking
areas custom fit their plows with rollers so that the blade remained about ˝ inch off the turf
and was able to keep the lot open for winter use.1 Most manufacturers of permeable
paver systems recommend the use of skids on the corners of snowplow blades. Manufacturers of
the interlocking pavement blocks, however, state that the structure of the blocks’ top edges
minimizes chipping and allows for normal plowing procedures. In general, as is always the case,
the use of salt can create a potential pollution problem (it is not removed by the permeable
paver system), and de-icing products adversely affect all concrete and turf materials.
When installed and maintained properly these systems are durable, although there will be some
unavoidable loss in water flow through the system over time. Some settling may also occur in
portions of the pavement due to poor compaction or construction control. A high failure rate for
these systems can usually be attributed to poor design, poor construction techniques, subsoils
with low permeability, and/or lack of adequate preventative maintenance.2
There are plenty of successful installations to turn to as examples, however. In Kinston, North
Carolina, a parking lot installed with concrete and grass pavers has been monitored since 1999.
Results from this study, along with similar research conducted in other parts of the United
States, show that permeable pavement can be very successful at reducing stormwater runoff if
proper engineering design, maintenance, and site selection are followed. The Kinston research
group recommends that permeable parking lots be maintained at least once per year to ensure the
highest level of permeability in the pavement.3 As a safety measure though, most
designs still tend to assume that a reduction in the pavers' infiltration capacity will occur
over time due to an accumulation of dirt and debris.
Concerns are often raised with permeable paver systems regarding the potential for groundwater
contamination. This is a threat that will depend on the amount of surface contamination, the
length of the filtration passage and the purifying effect of the soil.4 Several studies
have shown, however, that most metals are retained on the paver's surface, the geotextile layer
or in the upper sediments below the paver system, even after several years of operation, with
migration depths varying by
constituent.5,6 The soils
beneath the pavers should generally be effective in detaining pollutants from infiltrated water,
although for areas of special concern, an impermeable barrier and a collection pipe can be used
to transport the filtered water for further treatment or disposal.
The primary maintenance requirement for permeable pavers is to clean the surface
drainage voids. Fine debris and dirt accumulate in the drainage openings and reduce the
pavement’s flow capacity. It is natural for clogging to occur over time, but routine
maintenance can reduce this problem. A maintenance checklist follows:
Inspection of the site should occur monthly for the first few months after
construction. Then inspections can occur on an annual basis, preferably after rain
events when clogging will be obvious.
Conventional street sweepers equipped with vacuums, water, and brushes can be used
to restore permeability. Vacuum sweep ideally four (4) times a year, properly
disposing of the removed material. Follow the sweeping with high-pressure hosing
of the surface pores. If necessary, add additional aggregate fill material made up
of clean gravel.
Potholes and cracks can be filled with patching mixes, and spot clogging of porous
concrete may be fixed by drilling approximately 0.5-inch holes every few feet.
Damaged interlocking paving blocks can be replaced.
An active street sweeping program in the site’s drainage area will also help to
prolong the functional life of the pavement.
Even though some irreplaceable loss in permeability should be expected over the
paver’s lifetime, you can increase the longevity of the system by following the
maintenance schedule for vacuum sweeping and high-pressure washing, restricting the
area’s use by heavy vehicles, limiting the use of de-icing chemicals and sand, and
implementing a stringent sediment control plan.
4 Borgwardt, S., 1999: Survey and expert opinion on the distribution,
performance and possible application of porous and permeable paving systems. Report commissioned
by MARSHALLS Mono Ltd., West Yorkshire.
5 Legret, M., V. Colandini and C. Le Marc, 1996: Effects of a porous
pavement with reservoir structure on the quality of runoff water and soil. The Science of
the Total Environment, 189/190, 335-340.
6 Smith, D.R. and D.A. Sholtis, 1981: Green Parking Lot (Dayton,
Ohio) - An Experimental Installation of Grass Pavement. Performance evaluation prepared by the
City of Dayton, Ohio. Order No. a-4331-2.