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Urban stormwater
has the potential to deliver large pollutant loads and
increased flows to receiving waters over short intervals.
The increased runoff has been shown to accelerate stream
bank erosion and reduce infiltration thereby increasing
drought effects on the headwaters of streams. Best
management practices are currently recommended by PaDEP to
control stormwater runoff. Detailed information on their
performance is still emerging as recognized by
Pennsylvania’s Chesapeake Bay Nutrient Reduction Strategy (PaDEP
1996a) and the Pennsylvania Handbook of Best Management
Practices for Developing Areas (PACD 1998).
An existing
traffic island was retrofitted to become a bio-infiltration
BMP. The facility intercepts flows that would normally be
captured by inlets and delivered through culverts to a dry
detention basin without a chance to cleanse or infiltrate
the stormwater runoff. Designed for the smaller storms (0 –
1.5 inches), the runoff infiltrates thereby reducing
downstream stormwater volumes, stream bank erosion, and
non-point source pollution to the headwaters of the Darby
Creek. The advantage of this type of facility is the capture
and infiltration of over 90% of the yearly rainfall. This
will significantly reduce stream bank erosion and protect
low baseflows during times of drought. As all the stormwater
for these rainfalls is infiltrated, there is NO pollutant
input to the headwaters for smaller storms.
During larger
storm events (2 – 100 year storms) a significant portion of
the rainfall, as well as the first flush of pollutants is
infiltrated. Flows over the capacity of the BMP go through
the original culvert system to a dry detention pond.
The
bio-infiltration pond is incorporated within the “Best
Management Practice Demonstration Park" on Villanova’s
campus, and joins the retrofitted stormwater wetlands,
infiltration trench, porous asphalt and porous concrete
site. To validate the performance of the device, rainfall
and groundwater depth are monitored. In addition to those
displayed on this website, results are included in the final
report to the PaDEP.
Download: PaDEP Final
Report
Presented at the ASCE EWRI
Congress, Philadelphia June 2003: Download Presentation
(pdf)
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