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The construction of the
Infiltration Trench began in the spring of 2004. The BMP was
retrofitted into a small area between an academic building and
a parking garage. Previously the area had a steep eroding
slope and was considered unsightly by the University. The
original stormwater system of the parking garage directed
runoff through piped gutters and concrete channels directly
into the road where it entered inlets and was piped to a local
stream. There were three main components included in the
design for the infiltration trench BMP:
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To collect and infiltrate
runoff from the upper deck of the adjacent bi-level parking
garage.
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To provide sufficient research
and demonstration opportunities for students to study the
BMP’s hydrologic and water quality performance.
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To improve the common area’s
aesthetic appeal and function for the University.
Before the Infiltration Trench
was built, a retaining wall was erected to stop the erosion of
the adjacent slope. The BMP’s construction entailed the
excavation of the trench, lining the trench with a geotextile,
filling the trench with stones to provide temporary storage,
and finally the laying of EP Henry Eco-Pavers to create a
pervious patio area for student and staff of the University.
A network of PVC pipes collect
runoff from approximately half of the parking garage
(~1/2acre). The flow is routed into a bench where debris and
sediment are removed. The flow is also measured and water
samples can be taken inside the bench. The flow then enters a
perforated distribution pipe where it is released into the
stone bed. The stone bed provides temporary storage as the
water slowly soaks into the surrounding soil. At the top of
the storage bed there is an overflow pipe that allows flows in
excess of the capacity of the trench to flow into an existing
stormwater inlet. During extremely intense periods of rainfall
the porous paver patio acts as a secondary overflow and the
water flows over a grass strip and into the same stormwater
inlet. One of the questions being answered through the ongoing
research at the Infiltration Trench is the question of
longevity. In order to maintain the infiltration capacity of
the soil it is necessary to remove as much sediment and debris
as possible. The inflow at the Infiltration Trench carries
some small debris and sediment. Inside the pretreatment /
monitoring bench a system of flow baffles and screens help
remove the trash and sediment that would otherwise find its
way into the stone bed.
Innovative Stormwater BMPs like
the Infiltration Trench are still relatively new to the
engineering profession. However in an effort to better manage
our water resources, recent stormwater regulations are placing
more emphasis on these types of practices. Therefore long-term
performance data on these BMPs is essential. The monitoring
and research being conducted at the Infiltration Trench
focuses on both water quantity and water quality. The site has
been instrumented to record rainfall, inflow, temperature, and
depth within the stone storage bed. These parameters are being
used to document how effective the BMP is at reducing the
volume of runoff from the parking garage. Groundwater samplers
(lysimeters) were installed at two and four feet beneath the
bottom of the trench. These water samples along with samples
taken from the inflow and from within the storage bed enable
the site’s water quality characteristics to be studied.
The Infiltration Trench is the
newest addition to the Villanova Stormwater BMP Research and
Demonstration Park. Currently there are three other BMPs on
campus including a Stormwater Wetlands, a Bio-Infiltration
Traffic Island, and a Porous Concrete Site. The BMP park has
been the subject of frequent tours which help educate both
local and international interest groups. |
