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Permeable Pavements: Lessons Learned from Practice and
Research
Pete Weiss, Valparaiso University John Gulliver, Univ. of Minnesota
Masoud Kayhanian, UC-Davis Lev Khazanovich, Univ. of Pittsburg
Full Depth Permeable Pavement X-Section
• Water infiltratesthrough permeablepavement surfaceand other layers
• Stored in gravel layer(~40% voids)
• Water infiltrates intosoil or is collected bydrain tile
Image: CAHILL Associates 2003
Project Scope • Full depth permeable
pavement:– Literature review
• Structural design• Hydrologic
design/performance• Water quality impact• Maintenance requirements
– Cold climate casestudies
– Research needs– Software to determine
feasibility of permeablepavement
Image: www.epa.gov
• Does not includepermeable friction course
Project Scope • Full depth permeable
pavement:– Literature review
• Structural design• Hydrologic
design/performance• Water quality impact• Maintenance requirements
– Cold climate casestudies
– Research needs– Software to determine
feasibility of permeablepavement
Image: www.epa.gov
• Does not includepermeable friction course
Benefits of Permeable Pavement
• Volume Reduction• Improved water quality• Hydroplaning resistance• Spray reduction
- Increased visibility• Smoother riding surface• Noise reduction• Less winter salt
application
Photos: Barrett 2008
Impermeable pavement
Permeable Pavement
Permeable Pavement Types • Porous Asphalt• Pervious Concrete• Permeable Pavers• Permeable Articulated
Concrete Blocks
ICPI SDRMCA
NAPA
Keys for Success • Proper Construction
– Mix design– Compaction– Void ratio– Curing
• Proper & regular maintenance
Photo courtesy of M. Maloney, Shoreview, MN
Summary of Hydraulic Performance • Surface infiltration rates decrease over time
but are not rate limiting• Need a methodology to determine
permeability of sub-base before design iscomplete
• Geotextile fabrics canreduce/eliminateinfiltration
• Infiltration rates aremaintained throughwinter
http://ih.constantcontact.com/
Summary of Water Quality Impact • Removes solids and solid-bound
contaminants• Mass load reduction often achieved through
infiltration • Nitrification may occur
(ammonium to nitrate)but total nitrogenremoval is low
• Dissolved phosphorusremoval is minimal
Photo: http://switchboard.nrdc.org/
Summary of Maintenance • Surface cleaning is effective but variable• Particle removal from surface is major issue• Pressure washing @ 45o and/or vacuuming/
regenerative air sweepers are most effective• Do not use brushes• Cleaning frequency = multiple times/year
Images: Elginsweepers.com
Vacuum Regenerative Air
Porous Asphalt Paired Intersections - Robbinsdale
Constructed 2009-2010
Construction in September 2010 (Wenck 2014)
• Objective was to evaluate possible reductions in salt loads onporous asphalt pavements
• Also durability, maintenance, and water quality
Paired Intersection Study
Wenck 2014
• TMDL study for Shingle Creek foundthat Cl loading must be reduced by 81%
• Two porous asphalt pavementintersection were constructed: one overa sand sub-base and the other over aclay sub-base.
• Designed to store the 2-yr storm• The porous asphalt sections were not
salted during the winter.• Conventional asphalt sections were
salted.
Paired Intersection Study
(thenewsherald.com)
Porous Asphalt Cross-Section (Wenck 2014)
Paired Intersection Study
6” drain tile
12” Reservoir Layer (1.5”-2.5” stone)
Geotextile
4” Asphalt Max 2” choker course (0.5” crushed stone)
• Each porous asphalt section wasapproximately 150 feet long and 28 feetwide for a total area of about 4200square feet.
• The cost of the porous asphalt installationat Site 1 was $42,670 and at Site 2 it was$32,200 ($7.5 - $10/SF).
• The difference in cost is likely due to thefact that at Site 1 construction wasnegotiated as part of a change order andat Site 2 the contract was awarded to thelow bidder.
Paired Intersection Study
• Reservoir temperatures in both PP systems duringwinter was consistently warmer than thepavement temperature
• Attributed to the air within the voids of thereservoir layer insulating the reservoir
• Insulation minimizes winter freezing and keepsreservoir temperatures cooler in spring
• Suggests winter infiltration into subgrade ispossible
Paired Intersection Study Results
• Conventional pavement sites were slushier than the porous asphalt sites due to infiltration into PP
• Bare pavement on the porous test sections was comparable to that on conventional asphalt sections but had a lag of 2 to several hours
Paired Intersection Study Results
Slush gathering and refreezing on the traditional asphalt at Site 1 on January 17, 2010
Paired Intersection Study
Slush free porous asphalt on January 17, 2010
Wenck 2014
Site 1 Test Section looking south
Paired Intersection Study
Wenck 2014
• The unsalted, porous asphalt sections had a similar amount of bare pavement compared to salted, conventional asphalt sections
• The porous pavement over sand subgrade was more effective for ice control compared to the porous pavement on clay subgrade
• Porous asphalt sections have been durable without any special snow plow equipment or adjustments
Paired Intersection Study Lessons Learned
• Effective maintenance on the porousasphalt sections appears to bevacuuming (regenerative) twice peryear and patching with traditionalasphalt, as necessary
• Porous asphalt intersections havepotential as an ice-controlmanagement practice in certainsituations
Paired Intersection Study Lessons Learned
• Permeable pavements can result in lower salt application rates in the winter months
• Permeable pavements can reduce runoff volume and improve water quality (with other benefits)
• Permeable pavements are more expensive • Construction and maintenance are critical to success • Maintenance is typically pressure washing and/or vacuuming • Permeable pavements can withstand harsh winters • Permeable pavements can maintain infiltration rates
throughout the winter
Conclusions
Research Needs • Structural/Construction: long-term performance,
aggregate grading, geotextiles, compactionenergy, in-situ tests, life-cycle cost analysis…
Permeable
• Hydraulic/WQ: mix designas pollution source,hydraulics w/ heavy loads,raised drain tile, long-termWQ, N/P fate..
• Maintenance: quantifyclogging, cleaningmethods, frequency,optimal pavement design…
http://www.vaasphalt.org
