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Photo illustrating pervious concrete. Pervious concrete is a special type of concrete with a high porosity that allows water from precipitation and other sources to pass directly through.

The most commonly used permeable pavement surfaces are pervious concrete, porous asphalt, and permeable interlocking concrete pavers. Lesser utilized options include plastic and concrete grids, as well as amended soils (artificial media added to soil to maintain soil structure and prevent compaction) (MPCA 2008). For the purpose of this document, the focus is on pervious concrete, porous asphalt and permeable interlocking concrete pavements.

Photo illustrating porous asphalt. Porous asphalt is standard hot-mix asphalt that allows water to drain through it.

Photo illustrating permeable interlocking concrete pavement. Permeable interlocking pavers consist of concrete or stone units with open, permeable spaces between the units.

For each of the above pavement surfaces, there are many variants depending on the design goals. For instance, permeable pavement can be installed with a deep underlying reservoir consisting of open-graded, crushed rock. This design provides water quality and quantity control by storing runoff and infiltrating it into the subgrade soils over an extended period of time. A second design variation includes a deep underlying reservoir consisting of open-graded, crushed rock above an impermeable layer of soil or a liner and an underdrain. The underdrain typically discharges to a stormwater pond or storm sewer system. This design provides some runoff flow attenuation, filtering, but no volume reduction. These two options provide different levels of treatment.

To assist with selection of a permeable pavement type, a general comparison of the properties of the three major permeable pavement types is provided in the table below. Designers should check with product vendors and the local review authority to determine specific requirements and capabilities of each system. Schematic cross sections of each system are illustrated in the design section for permeable pavement.

Summary of properties of permeable pavements.
Link to this table

Properties	Pervious concrete	Porous asphalt	PICP
Typical pavement surface thicknessa	5 to 8 inches	3 to 4 inches (thicker for high wheel load applications)	3 inchesa
Bedding layera,f	None	1 in. AASHTO No. 57 stone	2 inches of AASHTO No. 8 stone (MnDOT 3127 FA-3)
Reservoir layerb,f	AASHTO No. 57 stone or per hydraulic design	AASHTO No. 2, 3, or 5 stone	4 inches of AASHTO No. 57 stone over No. 2, 3 or 4 stone
Construction properties	Cast in place Seven day cure Must be continuously covered	Cast in place 24 hour cure	No cure period Manual or mechanical installation of pre-manufactured units
Installed surfacing costc	3 to $4/square foot	$2/square foot	3 to $4/square foot
Minimum batch size	None
Longevityd	20 to 30 years
Overflow	Catch basin, overflow edge, elevated underdrain
Runoff temperature reduction	Cooling at the reservoir layer
Surface colors/texture	Range of light colors and textures	Black or dark grey colors	Wide range of colors, textures and patterns
Load bearing capacitye	Handles all vehicle loads with appropriate surface and base/subbase layer material and thickness design
Surface cleaningg	Periodic vacuuming; replace if completely clogged and uncleanable		Periodic vacuuming; replace jointing stones if completely clogged and uncleanable
Other issues	Avoid concentrated deicers Avoid winter sanding	Avoid seal coating Avoid winter sanding	Avoid winter sanding
Design references	[1]	[2]	[3]

^aThickness may vary depending on site and traffic conditions
^bReservoir storage may be augmented by corrugated metal pipes, plastic arch pipe or plastic lattice crates
^cSupply and install minimum surface thickness only; minimum 30,000 sf with Minnesota 2012 prevailing labor wages. Does not include base reservoir, drainage appurtenances, engineering, or inspection
^dBased on pavement being properly maintained. Resurfacing or rehabilitation may be needed after the indicated period
^eDepends primarily on on-site geotechnical considerations and structural design computations
^f ASTM D448 Standard Classification for Sizes of Aggregate for Road and Bridge Construction or ASASHTO M-43
^gPeriodic vacuuming frequency determined from inspection, intensity of use, and other potential sediment sources

Photo illustrating porous asphalt. Porous asphalt is standard hot-mix asphalt that allows water to drain through it.

Photo illustrating permeable interlocking concrete pavement. Permeable interlocking pavers consist of concrete or stone units with open, permeable spaces between the units.

For each of the above pavement surfaces, there are many variants depending on the design goals. For instance, permeable pavement can be installed with a deep underlying reservoir consisting of open-graded, crushed rock. This design provides water quality and quantity control by storing runoff and infiltrating it into the subgrade soils over an extended period of time. A second design variation includes a deep underlying reservoir consisting of open-graded, crushed rock above an impermeable layer of soil or a liner and an underdrain. The underdrain typically discharges to a stormwater pond or storm sewer system. This design provides some runoff flow attenuation, filtering, but no volume reduction. These two options provide different levels of treatment.

To assist with selection of a permeable pavement type, a general comparison of the properties of the three major permeable pavement types is provided in the table below. Designers should check with product vendors and the local review authority to determine specific requirements and capabilities of each system. Schematic cross sections of each system are illustrated in the design section for permeable pavement.

Summary of properties of permeable pavements.
Link to this table

Properties	Pervious concrete	Porous asphalt	PICP
Typical pavement surface thicknessa	5 to 8 inches	3 to 4 inches (thicker for high wheel load applications)	3 inchesa
Bedding layera,f	None	1 in. AASHTO No. 57 stone	2 inches of AASHTO No. 8 stone (MnDOT 3127 FA-3)
Reservoir layerb,f	AASHTO No. 57 stone or per hydraulic design	AASHTO No. 2, 3, or 5 stone	4 inches of AASHTO No. 57 stone over No. 2, 3 or 4 stone
Construction properties	Cast in place Seven day cure Must be continuously covered	Cast in place 24 hour cure	No cure period Manual or mechanical installation of pre-manufactured units
Installed surfacing costc	3 to $4/square foot	$2/square foot	3 to $4/square foot
Minimum batch size	None
Longevityd	20 to 30 years
Overflow	Catch basin, overflow edge, elevated underdrain
Runoff temperature reduction	Cooling at the reservoir layer
Surface colors/texture	Range of light colors and textures	Black or dark grey colors	Wide range of colors, textures and patterns
Load bearing capacitye	Handles all vehicle loads with appropriate surface and base/subbase layer material and thickness design
Surface cleaningg	Periodic vacuuming; replace if completely clogged and uncleanable		Periodic vacuuming; replace jointing stones if completely clogged and uncleanable
Other issues	Avoid concentrated deicers Avoid winter sanding	Avoid seal coating Avoid winter sanding	Avoid winter sanding
Design references	[4]	[5]	[6]

^aThickness may vary depending on site and traffic conditions
^bReservoir storage may be augmented by corrugated metal pipes, plastic arch pipe or plastic lattice crates
^cSupply and install minimum surface thickness only; minimum 30,000 sf with Minnesota 2012 prevailing labor wages. Does not include base reservoir, drainage appurtenances, engineering, or inspection
^dBased on pavement being properly maintained. Resurfacing or rehabilitation may be needed after the indicated period
^eDepends primarily on on-site geotechnical considerations and structural design computations
^f ASTM D448 Standard Classification for Sizes of Aggregate for Road and Bridge Construction or ASASHTO M-43
^gPeriodic vacuuming frequency determined from inspection, intensity of use, and other potential sediment sources