Why Use Pervious Concrete?
To meet federal and local clean water regulations.
The U. S. Environmental Protection Agency Phase II regulations
require owners of newly developed (or redeveloped) sites of 1 acre
or more to have an on-site management system or treating storm
water. The EPA has recognized pervious concrete as a Best Management
Practice (BMP) for meeting its requirements.
To reduce costs.
Although pervious concrete pavement may be more expensive than
typical concrete pavement, the project cost
can be offset by reducing or eliminating the need for drainage
systems and retention ponds and their associated
construction and maintenance costs. Other project cost savings
include:
- Reduced Grading. With no storm drains there is no need to slope
the parking area.Pervious Concrete accepts the existing topography
of the area.
- No storm sewer tie-ins. Eliminating the cost of underground
piping and drain inverts can be a substantial savings.
- No additional stormwater pollution prevention devices. For
example, sewer invert filtration systems are unnecessary. Costs
savings here are both up front and long term.
To gain green building LEED credits.
Using pervious concrete can be part of a strategy that helps a
project meet sustainability goals and gain valuable LEED credits.
Possible contributions include:
- Stormwater Management. Pervious paving reduces stormwater flow
and pollutant loads. Can contribute to LEED Credit 6.
- Heat Island Effect. The light colored surface can increase
reflectivity and reduce heat build up.May contribute to LEED
Credit SS 7.
- Minimize Site Disturbance. By integrating paving and drainage,
less site area may need to be used, allowing a more compact site
development footprint. May contribute to LEED Credit SS 5.
- Recycled content. Fly ash, slag cement, or silica fume can
substitute partially for cement, andrecycled aggregates can replace
new gravel in the subgrade. Recycled content may contribute to
LEED Credit M 4.
Natural Stormwater Management
Pervious concrete has the same water management characteristics
as grass and other ground covers. Pervious
concrete parking lots, driveways, sidewalks and roads allow the
rain to wash directly into the ground or sub-base,
naturally filtering out pollutants while replenishing the water
tables and aquifers and watering surrounding
vegetation. Pervious concrete is a unique mix of cementitious materials,
course aggregates (gravel or crushed stone)
and water with little or no sand. The exclusive use of coarse aggregates
creates 15-25% air voids throughout the
concrete. These large gaps allow water to pass directly through
the pavement and into the soil or base rather than
collecting on or running off the surface. Pervious concrete can
pass 3 to 5 gallons of water per minute through its
open cells for each square foot of surface area. This works out
to more than 200 inches per hour which
is far greater than most rain events.
Profitable Ecology
Pervious concrete can also help to increase profitability while
providing environmental benefits. Traditional stormwater management
system can take up 10 to 20 percent of the overall site for retention
sites and bio-swales.
Pervious concrete can double as a parking facility and stormwater
treatment system, so this valuable space can be used to increase
the density of development. In addition, tree wells can be very
small since pervious concrete provides air and water to the tree
roots. This increases the amount of usable space for parking while
encouraging tree growth that cools the lot and improves the air
quality. The durability of concrete also lowers the overall lifecycle
cost with an expected life span of 20-40 years.
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