|
The porous asphalt parking site
was developed in June 2006 as part of the reconstruction of
the Univeristy’s athletic building, the Pavilion. The site
previously consisted of a temporary gravel parking lot and a
grass drainage swale. This best management practice (BMP),
in conjunction with an underground retention basin,
satisfies the runoff reduction required by state and local
regulations for the development of the site. Monitoring and
testing this site could help determine the effectiveness of
such BMPs which are becoming more and more popular in
construction as runoff reduction elements.
Traditional asphalt is not
porous which means nearly all of the rain that hits it runs
over the surface and straight to a storm water collection
system. The development and addition of such impervious
surfaces to watersheds leads to increased runoff and higher
flows downstream during precipitation events. These flows
lead to erosion and degradation of quality in the streams
and rivers.
Porous asphalt allows water to
pass through it and back into the natural groundwater table.
This not only replenishes the groundwater which is of
concern but also decreases the amount of runoff which
alleviates some of the stress applied to the streams. The
BMP is designed to handle the smaller storms (<.2”) which
comprise the majority of the annual rainfall (90%). The
theory is that this reduction in total volume will reduce
the amount of erosion downstream. Larger storm events
accommodated as well as overflows enter a stormwater
collection system through perforated pipe and a surface
inlet. At this site, the porous asphalt was utilized in a
portion of the parking lot and spans 20 parking spaces as
can be seen in the Figure below.
Figure 1: Completed porous asphalt parking site.
Porous asphalt is best fit for
parking spaces since the traffic is less there than on
actual driving surfaces where the stress on the surface
could cause deterioration. The rain that falls directly on
the parking spaces as well as the runoff from surrounding
areas that are not porous is able to infiltrate the surface.
The design consists basically of the porous asphalt surface,
a crushed rock storage bed and perforated PVC underdrain
system to deal with higher flow events and allow
installation of monitoring equipment.
The porous asphalt site is
incorporated within the “Best Management Practice
Demonstration Park" on Villanova’s campus. It adds to the
list of BMPs in use on the University’s campus and will be
monitored and evaluated to determine its effectiveness. |
