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Stormwater BMPs at UNC

A number of structural stormwater BMPs have been incorporated into the construction and renovation of new buildings, parking lots, and athletic fields on UNC owned properties. These structural BMPs include the construction of porous pavements, vegetated roof systems, cisterns and infiltration beds.

Porous Pavement

Installation of gravel infiltration bed at Estes Drive Extension porous parking lot
Installation of gravel infiltration bed at Estes Drive Extension porous parking lot

Porous pavement is simply a type of asphalt or concrete pavement that allows water to drain through due to its coarse structure. Allowing water to permeate through is important for recharging the water table and preventing pollutants from being washed into waterways. Non-porous pavement does not allow water to go through, causing stormwater runoff. UNC currently has a number of porous pavement parking lots that have infiltration/storage beds located beneath the pavement: Estes Drive Extension parking lot, the Park and Ride Lot next to the Friday Center on N.C. 54, the McCauley Lot across from the Cheek-Clark Building, and the Chatham County Park and Ride Lot.

Vegetated Roof Systems and Roof Gardens

Sedum on the Carrington Hall roof

Vegetated roofs systems consist of membranes, soils and plantings that are placed on top of buildings and help to hold precipitation and prevent runoff. In spring 2005, the construction of two vegetated roofs was completed on campus at the Carrington Nursing School and atop Rams Head Center. The vegetated roof at the Rams Head Plaza has a soil layer that is thick enough to support trees that will eventually grow to heights of 40 – 60 feet. In 2007, another vegetated roof was installed at the FedEx Global Eduation Center. In the case of both the Rams Head Plaza and the FedEx Global Education Center, water from excess runoff is also collected in cisterns.


Cistern installation at Fedex Global Education Center

In addition to an infiltration bed installed underneath Hooker Field, there is also an underground cistern that collects runoff from the artificial turf field as well as roof runoff from surrounding buildings. The water collected is used to irrigate nearby grass athletic fields. Above ground cisterns are also used in the capturing of roof runoff for irrigation. The Rams Head Plaza has a cistern that collects roof runoff. The water is then used to irrigate trees and lawns on the plaza area. The Fedex Global Education Center cistern to provides water for toilet flushing in the building.

Infiltration Beds

Installation of gravel infiltration bed at Hooker Field

In addition to parking lots, athletic fields and intramural play fields can be used as storage/infiltration beds. These storage/infiltration beds are important to replenishing the groundwater supply and to retaining stream base flow during dry weather. Athletic fields with storage beds have been created by first installing the stormwater storage or infiltration bed of gravel, covering the gravel with a geotextile fabric and then covering this with artificial turf. On the UNC campus infiltration beds were installed at both the Ehringhaus (near the Rams Head Plaza) and Hooker recreational fields. The infiltration bed at Hooker Field can hold up to 500,000 gallons that will eventually go back to the water table or be pumped out for irrigation of adjacent fields. Hooker field holds the water that is collected from roofs of adjacent buildings.

Water Quality Inlets

Area drains with water quality inserts at Rams Head Plaza

An inexpensive approach to Structural BMPs for removing pollutants is the use of water quality inlets. These are collection boxes that prevent trash and debris from entering the stormwater system. In order for these units to be effective they must be cleaned and maintained every three months. Water quality inlets are in use on the vegetated roof at the Rams Head Plaza. These inlets prevent solids from entering the cisterns.

Non-Structural BMPs

There are a number of Non-Structural BMPs that have been incorporated in the UNC-Chapel Hill campus to prevent pollutants absorption into stormwater runoff. These include: street and parking lot vacuuming, stormwater plantings, and education.

Street Sweeping/Pavement Cleaning

Regenerative sweeper truck sweeps and vacuums at the same time. Campus lots are vacuumed at least once per quarter.

Street Sweeping is a non-structural BMP that is intended to remove pollutants from land surfaces. The most effective way of using street sweeping to prevent pollutants from entering the water system is to clean areas with high debris on a regular basis. The street sweeper at UNC is also used to maintain the porous pavement parking lots at UNC.

Stormwater Plantings

Stormwater plantings near Lenoir Dining Hall

One of the easiest and most attractive way to increase the amount of stormwater returning to the water table as well as prevent pollutants from entering streams is to use stormwater plantings. This can be as simple as converting paved areas or turf areas to perennial beds and trees. The UNC Grounds Department holds contests and awards prizes to Grounds employees who suggest suitable locations for incorporating stormwater plantings on campus.

Education and Outreach

The UNC Department of Environment, Health, and Safety has a number of public education and outreach programs to further stormwater education and provides educational materials to students, faculty, and staff. Some of these programs include drain marking sessions with students, volunteer stream clean up days, and educational seminars open to the entire UNC community.

Vegetated Swales

At the Rams Head Plaza, water sometimes fills the cistern and vegetated roof and then pours into a vegetated swale.

During heavy rains, water fills the cistern and vegetated roof system at the Rams Head Plaza and overflows into a vegetated swale. Vegetated swales are sloped, shallow ditch-like features that contain vegetative plantings. As water flows through the swales, stormwater pollutants are removed from the water.