Pervious Pavements for
a More Livable Environment
 Pervious
pavements are less able to absorb and store heat than conventional
pavements. The lower
density of the material (15 - 25% void spaces) reduced heat
storage capacity. The lighter colors of some porous pavement
systems reduce the heat absorbing capacity of the pavement. The
open void structure in the porous pavement allows cooler earth
temperatures from below to cool the pavement. These factors
allow porous pavement systems to approach natural ground cover
in heat absorbing and storage capacity.
Unlike traditional concrete or
asphalt, pervious pavements typically provide a void content of
15-25%, offering improved filtration and an enormous amount of
surface area to catch oils and chemical pollutants. Some experts
believe that the bacteria living in these spaces break down
pollutants preventing much of the polluted runoff that normally
occurs with traditional pavements. Parking lots, in particular,
hold a tremendous potential for this material because of the
amount of oil and other hydro-carbon liquids that seep from
parked cars. |
|
Pervious pavements
can be made of concrete, asphalt, open-celled stones, and
gravel, that are mixed in a manner that creates an open cell
structure allowing water and air to pass through. Certain types
of porous pavement can pass 3-5 gallons of water per minute,
which is far greater than most conceivable rain events and
highly effective in controlling stormwater drainage. |
 |
Because pervious pavements allow rainwater to seep into the
ground through the pavement:
- Vegetation is
watered, reducing
the need for irrigation
- Ground water
is recharged
- Water
resources are preserved
- Stormwater runoff is reduced
- Stormwater
runoff quality is
improved
|
|
The
strength and durability of pervious pavement appears to be equal
to traditional materials. There are several examples of parking
lots built more than twenty years ago with pervious pavement
that are still structurally sound and in use. Pervious pavement
is also less susceptible to freeze-thaw cracking, due to large
void spaces.
Concerns about
clogging of pervious pavements can be "designed out", by
reducing erosion and sediment runoff through strategic design
and water retaining ground cover. Studies indicate that pressure
washing a "clogged" pervious concrete pavement can restore
80-90% of the permeability. |
 |
|
A new mind set is
needed when designing stormwater management systems. Rather than
designing a system to pass huge storm events (that may occur
only twice a century) rapidly from an area, water management
planners should consider the benefits of capturing and
recharging water from the smaller, more frequent rain intervals.
Atlanta, for example, receives significantly more than half its
annual rainfall from precipitation events of less than an inch.
The ecosystem lives and dies on daily events. A stormwater
system incorporating pervious pavement will be much more
effective in reducing total runoff and increasing the amount of
filtered groundwater. The material's ability to retain
stormwater while improving water quality and enhancing tree and
vegetation growth, makes this material a very exciting example
of green and sustainable building practice. |
For additional
information, visit:
www.pervious.info
|
