George Mason University
OP-23: Stormwater Management

The Storm Water Management Program at George Mason University (Mason) consists of minimizing the impacts of runoff associated with land disturbance such as flooding, erosion and water pollution. Due to current developmental expansion, Mason’s goal is to find cost-effective alternatives that provide water quantity and quality control while complying with laws and regulations. Moreover, as land disturbing activities take place, Mason continues to incorporate measures that protect and/or improve natural areas during and after construction. In addition to the ongoing efforts to preserve the natural landscape, Mason strives to reduce impervious areas as much as possible and create more vegetated regions.

In 2006, George Mason University constructed its first vegetated roof located in Fairfax campus, outside of Research I building. The facility covers an area of approximately 64 X 16 square feet filled with a variety of hardy and aesthetically pleasant plants that seamlessly blend into landscaping. The filtration properties of this facility help to eliminate pollutants while reducing storm water runoff.

In the ongoing effort to reducing impervious areas, George Mason University (Mason)continues to enhance the implementation of porous pavement. Mason currently contains more than one acre of pervious pavement in Fairfax campus. Permeable pavement is mainly used in low-traffic areas such as back roads, housing facilities and bike racks. The use of pervious pavement not only reduces the runoff concentrations but also enhances the natural process of filtration.

George Mason University (Mason) has currently two retention (wet) ponds serving as both storm water management (SWM) and best management practice (BMP) facilities. The first retention pond is located on the south-east portion of Fairfax Campus (Mason Pond). Mason Pond treats approximately 125 acres, which is equivalent to more than a third of the total campus area. It retains nearly 8 acre-feet of storm water and it outfalls into an existing detention pond (Braddock Pond) located south-west of campus. The second pond (Prince William Pond) is located in the middle of Prince William campus and it treats close to 60 acres of the site. Prince William Pond discharges into an existing unnamed tributary.

Though not engineered, George Mason University’s Grounds Department utilizes existing river stone swales as a method to mitigate existing drainage problems.

At George Mason University (Mason) there are several vegetated swales which treat, convey and partially infiltrate storm water runoff at different locations of Fairfax and Prince William Campus. In some cases, these swales are implemented in conjunction with other structures such as check dams, which are used to slow runoff and enhance infiltration, where steep slopes are present. Such swales are vegetated with water-resistant plants. A variety of small grass swales can also be found on the west side of Fairfax Campus; these work essentially as drainage ditches, but they latently provide more infiltration and pollutant removal. All of Mason’s existing swales are used mostly as pre-treatment for other existing SWM/BMP facilities.

Other technologies used in storm water management at George Mason University (Mason) include: 1. Detention Ponds: There are two existing detention (dry) ponds used as both SWM and BMP facilities. a. Krasnow Pond: Located north-east of Fairfax Campus. It treats a drainage area of 7.5 acres and outfalls into an existing unnamed tributary. b. FSH Pond: Located north-east of Fairfax campus. It treats a drainage area of 14.7 acres and outfalls into an existing unnamed tributary. 2. Extended Detention Ponds: Braddock Pond: Located south-west of Fairfax Campus. It treats a drainage area of 190 acres and serves as an outfall for Mason's East Fairfax Campus. 3. Rain Gardens: Mason has three rain gardens located on north-east portion of the Fairfax Campus. Each rain garden is composed of a variety of native perennial plant species, which require minimal maintenance (wildflowers, shrubs and small trees). Rain gardens allow the storm water to penetrate into the ground and restore the water table, while simultaneously removing pollutants. 4. Grasscrete: A pre-fabricated structure made out of reinforced concrete with voids to be filled with grass. Grasscrete has been installed as an alternative to ordinary concrete in different locations within Fairfax and Prince William campuses, such as, fire access roads, low-traffic roads, and other areas where emergency traffic is required. Its drainage capabilities are roughly the same as regular grass; therefore, Grasscrete has been beneficial in Mason’s effort to reduce impervious areas.