Environmental Engineering Reference
In-Depth Information
• Eliminate curing time and stress cracking or degradation of the surface that is
typically found in traditional asphalt due to the numerous joints in the pavers
• Eliminate visible cuts and resurface scars seen in traditional asphalt or concrete
when underground repairs are made
• Eliminate buckling or building due to heat and weight of vehicles as can be seen
in traditional asphalt
• Reduce surface heat load due to reduction in surface area compared to impervious
materials
The pavers can be installed with a different colored paver designating a parking space stripe
or lane stripe thereby eliminating repainting for the life of the pavers—approximately 20
years. Pavers can also be sealed, which reduces any stains that may occur due to oil spills
or other spilled substance, but this can affect the porosity. As with any porous pavement,
some reduction in porosity may also occur due to organic growth and fine accumulation,
but these pavers generally maintain porosity for a greater time frame than porous asphalt,
which requires cleaning yearly. The pavers should be cleaned every 3-5 years—a 4 year
cycle is recommended—with a commercial street sweeping or vacuuming equipment.
Additional aggregate fill material can be added to the openings at the same cleaning time,
if necessary.
The recommended concrete pavers can provide a low runoff coefficient of 0.3-0.5 as
compared to a higher traditional asphalt or concrete runoff coefficient of 0.95. Studies have
proven that these pavers can, depending on the subbase soil and surface slope, infiltrate up
to 5 in. of rainfall per hour prior to becoming saturated. Use of these pavers provides a sur-
face that is 70%-100% pervious and not a surface that is 70%-100% impervious like tradi-
tional asphalt and concrete. Studies have shown that permeable pavers are more expensive
to install than the traditional asphalt, but are less costly than asphalt to maintain over time.
Following are some initial typical cost guidelines in a per square feet installed price format:
Asphalt: $0.50-$1.00
Porous concrete: $2.00-$6.50
Grass/gravel pavers: $1.50-$5.75
Concrete pavers: $5.00-$10.00
A more accurate price comparison would involve the cost of a full stormwater manage-
ment paving system where the full system with asphalt and storm drains, catch basins,
and ungrounded pipes could be closer to $9.50-$11.50/ft
2
installed and the concrete paver
costs would remain closer to $5.00-$10.00/ft
2
installed. Use of the concrete pavers would
eliminate the need of traditional stormwater infrastructure. All of these prices are esti-
mated per manufacture guidelines and would need to be verified for any project to under-
stand a precise cost comparison. The cost of eliminating retention basins and increased
buildable area or smaller site requirements could also be added into the cost to give an
even larger long-term price difference.
21.5.2.6 Mulches
All passive rainwater harvesting structures should include a top mulch layer to assist in
reducing evaporation of the stormwater runoff captured in the structures. Mulches can be
organic or inorganic as long as they do not inhibit infiltration.
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