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(.00 to .00 per square foot.) In general, the multifunctional nature of permeable
pavers reduces overall costs.
Maintenance Issues. After installation of a permeable paver system,
maintenance is 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). 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 be required after cleaning.
Corrective Actions. If there is an extensive buildup of a "scum" layer within
the voids, the chip stone should be vacuumed, power-washed, cleaned and replaced.
In case of localized settling, individual paver blocks can be removed, new gravel added,
and the blocks replaced. In case of spills or contamination, the blocks and gravel layers
can be removed and the area remediated.
PERMEABLE PAVEMENT can be either asphalt or concrete. As with
permeable pavers, water is allowed to pass through voids and infiltrate into the
underlying soil. Permeable pavement lacks most of the fine material found in
conventional pavements, allowing water to flow through voids in the aggregate. (By
contrast, paver blocks themselves are not necessarily permeable; infiltration occurs in
the gaps between the blocks.) A layer of clean, uniformly graded gravel lies beneath
the pavement, and geotextile separates this stone bed from the soil below. Runoff from
the paved surface and adjacent impervious areas slowly passes through the gravel
layer, which also may serve as a storage area. Permeable pavement has the same
structural properties as conventional pavement. Environmental benefits are similar to
other IMPs: reduction of runoff volume and rate, pollutant filtering, flow dispersion, and
groundwater recharge. In addition, permeable pavements reduce the footprint of a
site's impervious area.
Most Appropriate Uses. Permeable pavement may be substituted for
conventional pavement in any application; however, it is most commonly and
successfully used in parking lots and walkways. Permeable pavements simultaneously
serve as hardscape and as stormwater infrastructure, and are therefore especially
practicable where space constraints preclude the use of other IMPs such as
bioretention. Cahill Associates reports that large permeable paved areas are still
functioning after 20 years, outlasting conventional pavements in some cases.
Permeable pavements reduce the likelihood of sinkhole formation because runoff is
dispersed over a large area (i.e., the entire paved surface), rather than concentrated in
a small area such as a pond or catch basin.34
Cahill Associates, 2003.