Worcester Polytechnic Institute
IN-15: Stormwater Modeling

Recent construction projects have incorporated LIDs as a standard practice. East Hall, opened in 2008, has a green roof which collects rainwater. The rainwater no longer drains directly to the street but is absorbed by the planting atop the roof. Additionally, two 25,000 gallon cisterns were installed to collect storm water runoff from the roof at the Sports & Recreation Center. Collected water is designed to be pumped for vegetation irrigation. The Park Ave Garage project utilized stormwater modelling, and it included the construction of two rain gardens located on the Higgins Lot to help manage storm water runoff from portions of the site entry drive and Higgins Parking. The rain gardens are LID measures that provide water treatment and attenuate increased peak rates of runoff. Also, the design of the subsurface infiltration system includes a permeable bottom that allows for maximum infiltration of the treated runoff from storm events up to the 100-year storm. The system can hold approximately 670,00 gallons of water, allowing much of this to infiltrate into the native soils and release in a controlled rate into the municipal system. At Faraday Hall, the grounds are irrigated by a water-conserving irrigation system combined with drip irrigation that reduces potable water use by at least 50%.

For question above regarding percentile, this information is unknown at this time.
The percentile local or regional rainfall event is an estimation.
The design of the draining under the Park Avenue garage is an example of stormwater modelling to assess the impact of LID practices and green infrastructure.