UDFCD position on the use of porous asphalt pavement
In April 2008, UDFCD worked with the Colorado Asphalt Pavement
Association (CAPA) and several pavement contractors to install a
porous asphalt demonstration pad in front of the City and County of
Denver's Wastewater Management building. This site has been
monitored regularly to determine if porous asphalt can maintain the
minimally acceptable infiltration rate for any permeable pavement
in the UDFCD region, which we have determined to be:
For the UDFCD-recommended impervious tributary area/pavement area
ratio of 2:1, this minimally acceptable infiltration rate is equal
to 20 inches per hour. Over a few years, the infiltration
rate at this site and several other porous asphalt installations in
the UDFCD region fell below this minimum standard and that cleaning
with reasonably available methods and equipment were generally not
successful in restoring infiltration rates to the minimum
acceptable level. To properly clean porous asphalt on a commercial
scale, regenerative air or vacuum sweepers are recommended.
More intensive cleaning with power washers and higher efficiency
vacuums was performed at some of these sites by CAPA and they were
generally able to restore infiltration rates via these more extreme
UDFCD considers porous asphalt an adequate BMP for use in
locations where clogging sources are minimal, traffic volume is
low, and maintenance is regular and intensive, but our experience
indicates that such locations are rare. The intent of the
USDCMV3 has always been to include only stormwater BMPs can be
widely used throughout the UDFCD region and that have a good chance
of success in capturing and treating the full design volume of
stormwater over the life of the BMP with only reasonable
maintenance practices and readily accessible equipment.
For this reason we will not at this time include porous asphalt
pavement in the USDCMV3 and we further recommend both caution and
realistic expectations in regard to performance and maintenance
costs when implementing this particular permeable pavement.
This memorandum applies only to porous asphalt pavement.
UDFCD continues to monitor and to recommend the use of other
permeable pavement technologies found in the USDCMV3 such as
permeable interlocking concrete pavement (PICP), concrete grid
pavement, porous gravel pavement, and reinforced grass
pavement. UDFCD will continue to monitor advances in porous
asphalt composition, mixing and placing, and will update this
position as appropriate.