design elements - San Jacinto Texas Historic District

Porous Pavements
Defi nition
Porous paving materials or paver units with
porous joints allow transmission of water
to an aggregate base, reducing runoff rates
and improving water quality. Runoff is
temporarily stored in the base and slowly
evaporated and released to storm sewers.
When porous paving systems are installed
over permeable soils, runoff volumes can be
reduced. Porous unit pavers are a common
type of porous pavement system that contain
openings fi lled with gravel or rock chips.
Porous concrete, and asphalt contain larger
than typical aggregates and pore spaces to
allow water percolation, but are less common.
Variations on gravel pavements are a third
type of permeable practice.
Applicability
Porous pavement is appropriate for new
and retrofi t projects on existing streets, full
and temporary (overfl ow and special event)
parking lots, alleys, sidewalks, utility and
access roads, emergency access lanes, fi re
lanes, and driveways. Porous pavements are
not appropriate for vehicle service stations,
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gas stations, and other areas used for transfer
or storage of hazardous materials, unless
they are properly lined.
Benefi ts
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Reduces stormwater runoff volumes
by 20% or more depending on depth of
the aggregate base and permeability of
underlying soils.
Reduces stormwater runoff rates by up to
95%.
Filters sediments, hydrocarbons, nutrients,
and other urban pollutants from runoff
and reduces runoff temperatures.
Can help meet detention requirements
and reduce stormwater conveyance and
detention infrastructure needs (detention
storage can be provided within the gravel
base below the surface.)
Reduces need for deicing salt and salt
impacts to water quality in cold climates.
Less ponding of water on the driving
or parking surface reduces skidding,
hydroplaning, and ice buildup.
Pervious pavers used in a road cross section with parkway bioswales.
Grasspave paving blocks.
Concrete pavers with interior spaces for drainage.
IMAGE: CONSERVATION DESIGN FORUM IMAGE: CONSERVATION DESIGN FORUM
IMAGE: CONSERVATION DESIGN FORUM