FAQs

Q: What is the BMP's drainage area?

A: The contributing area is approximately 20,400ft2 or about 1/2 acre. The area consists of a Villanova University parking deck and is 100% impervious.

Q: What watershed is the site located in?

A: The Infiltration Trench is located in the headwaters of the Mill Creek watershed which drains into the Schuylkill River. Both of which are part of the Delaware River watershed.

Q: What kind of maintenance is required?

A: Sediment and small debris periodically (monthly basis) need to be removed from the pretreatment bench.  Additionally, instrumentation should be calibrated several times a year.

Q: How is the inflow monitored for the BMP?

A: The inflow is monitored using a pressure transducer and a V-notch weir. The weir equation can be applied to the transducer readings to calculate the flow.

Q: What water quality parameters have been monitored at this BMP?

A: pH, Conductivity, Copper, Total Nitrogen, Total Phosphorus, Chloride, Total Suspended Solids, and Total Dissolved Solids.

Q: What depth of rainfall was this BMP designed for?

A: The Infiltration Trench was designed for a smaller amount of rain (0.3 inches) to cause it to be stressed more frequently for research purposes. The infiltration rate of this site is considerably larger (for the same footprint) than the other BMP sites since it is deeper and the sides contribute greatly to the infiltration volumes; the ratio of the drainage area to the surface area of the infiltration trench is nearly 160 to 1. The results of this project could change the way these BMPs are designed.

Q: What happens to this BMP when the rain event exceeds design limits?

A: The Infiltration Trench has an overflow pipe that allows excess runoff to enter the existing Villanova University stormwater piping system. Porous Eco-pavers are also installed at the ground surface to allow water to escape through the surface during more extreme rain events.

Q: What size rain events typically create overflow from the BMP?

A: Due to the rapid infiltration rate of the Infiltration Trench, overflow is typically not observed from events that are less than 0.25 inches (assuming the trench is empty at the onset of the rain event).

Q: What factors have shown to have the greatest effect on the performance of this BMP?

A: Research since the trench's inception has shown that infiltration rates respond to temperature, antecedent dry time since the last rain event, rain event duration, and total precipitation.  Furthermore, a significant decline in performance has been shown due to the large, impervious area draining to the Infiltration Trench.

Q: How long does the Infiltration Trench typically take to completely empty (assuming full)?

A: Initially, depending on the environmental factors described above, it can take anywhere from 5 to 7 days for the trench to completely empty.  However, after over a decade of use, the bottom has become clogged and infiltration only occurs out of the sides of the Infiltration Trench.  There is typically some level of water always present in the Infiltration Trench.