University of North Carolina at Chapel Hill
OP-27: Rainwater Management

UNC operates its own stormwater management program under a National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Phase II permit. The UNC stormwater staff conducts activities that meet the six minimum measures of the NPDES Phase II permit plus other activities that meet regulatory, infrastructure management, and sustainability goals. These programs cover the following areas: staff stormwater education and good practices, mapping, illicit discharge detection and elimination, public involvement, construction site erosion and sedimentation control, post-construction stormwater management, stormwater system maintenance, stormwater system condition evaluations, and stormwater retrofitting. New development and redevelopment projects address water quality, stormwater runoff volume, and peak discharge rate. All projects are reviewed by the UNC Stormwater Engineer, the Town of Chapel Hill Stormwater Department and/or the State Division of Water Quality Stormwater Permitting Unit. The University of North Carolina at Chapel Hill Stormwater Performance Criteria, Design Standards, and Procedures can be found here: https://share.campus-services.unc.edu/Policy/EnergySvcs/Energy%20Services%20Design%20Guidelines/SW-Design-Guidelines.pdf The UNC structural stormwater system is comprised of thousands of catch basins, inlets, and outfalls, miles of piping, and over 200 stormwater management practices. UNC property drains to Meeting of the Waters Creek, Battle Branch, Chapel Creek, Morgan Creek, Crow Branch, Booker Creek, Bolin Creek, and Little Creek. UNC is located within the Jordan Lake Watershed within the Cape Fear River Basin.

UNC has over 200 stormwater management practices in use. Traditional measures include ponds, wetlands, underground storage, bioretention, and sand filters. More innovative control measure include green roofs, permeable pavement, infiltration beds, vegetated swales, cisterns, and underground water quality improvement devices.

Multiple campus rooftops drain to cisterns that hold rainwater for reuse on landscapes and in toilets.

sand filters

Six locations at UNC incorporate green roofs: Rams Head Plaza, Carrington Hall / Nursing School Addition, FedEx Global Education Center, Genome Sciences, Koury Oral Health Sciences, and the Loudermilk Center. The Rams Head Complex, the Nursing School addition, the FedEx Global Education Center, and the Genome Sciences Building were each constructed on top of a former surface parking lot. So the impervious surface area at each site was reduced by constructing the building and incorporating a green roof. Located within a short walk of 8,000 residential students and most campus classrooms, Rams Head Center is part of the new connective tissue bridging South Campus and Main Campus. The facility boasts a grocery store, dining hall, recreation center, intensive green roof, and two large rainwater cisterns all built around a 700- space parking garage. Completed in 2005, the Nursing School addition was the first building in the UNC system to receive Leadership in Energy and Environmental Design (LEED) certification from the U.S. Green Building Council. Its extensive green roof captures rain water, reduces stormwater runoff, and provides attractive views from adjacent offices. Opened in 2007, the FedEx Global Education Center features two extensive green roofs, which contain drought-tolerant sedum gardens. The roofs minimize stormwater runoff, reduce the urban heat island effect, and provide an attractive view from the adjacent outdoor terrace. The stormwater from that falls on the Rams Head Plaza buildings and the Fedex Global Education Center is also collected in cisterns. At Rams Head, the overflow from the intensive green roof passes through a bioswale on its way to an infiltration bed that underlies a recreation field.

UNC has 12 porous pavement installations. Six installations occur at four park and ride parking lots that have infiltration/stone storage beds located beneath the pavement. These include: Estes Drive Extension parking lots (one permeable asphalt; one permeable concrete), the Park and Ride Lots next to the Friday Center on Highway 54 (one permeable asphalt; one permeable concrete), at the Hedrick building (permeable asphalt), and the Chatham County Park and Ride Lot (permeable asphalt). The NC Botanical Gardens Education Center (permeable interlocking concrete pavers) is a new highly visible site. Additional smaller parking installations have occurred at the McCauley Lot across from the Cheek-Clark Building (permeable asphalt), EPA Building (permeable asphalt), Baity Hill Residence Halls (permeable asphalt), and the Kenan/McIver Residence Halls (permeable asphalt).

UNC has 17 ponds and wetlands. These are primarily dry detention basins located off main campus or on the southern edge of campus. These are under consideration for retrofit as wetlands or wet ponds. UNC also has 31 stormwater management practices that were designed for infiltration. Eight of these sites are also permeable pavement. The other sites are underground storage in conjunction with an underground stone bed designed for infiltration. While these are not ponds, they are considered "retention."

The University has one installation that is a vegetated swale designed for stormwater treatment. During heavy rains, water fills the cistern and vegetated roof system at the Rams Head Plaza and overflows into a vegetated swale. UNC also has six level spreaders, which are a form of vegetated conveyance. These spread water to promote sheet flow. Four level spreaders are located at the Baity Hill Residence Halls. One is located at the Francis Owen facility. One level spreader is located near the Giles Horney Building. The University's open channel conveyances include many vegetated and grassed swales. If these were not specifically constructed as a stormwater treatment practice, we do not inventory them as stormwater management.

Rainwater collected from the roof of the Genome Sciences Building drains to a 350,000 gallon, stone-filled cistern beneath the Bell Tower Amphitheater. Following UV treatment and chlorination, the rainwater is used to flush 1000 toilets in the Genome Sciences Building and Kenan Stadium and to irrigate Kenan field. When rainwater is sufficient, reclaimed wastewater from OWASA provides a non-potable backup. Concrete vaults detain ground-level stormwater. Short-term storage reduces downstream erosion, flooding, and pollutant loading. Staff stormwater education and good practices: Stormwater staff from the UNC Department of Environment, Health, and Safety (EHS) conduct periodic training for 950 UNC staff whose actions on the job influence water quality. This includes staff from the following departments: Grounds, Athletics, Facilities Maintenance, Housekeeping, Energy Services, Public Safety, Construction Shops, and Housing Support. Prior to the training, less than 25% of pollution reports came from outside of EHS. After the first round of training, more than 65% of pollution reports come from outside of EHS. Mapping: UNC Energy Services has mapped the structural system in GIS, including the stormwater treatment practices, storm drain pipes, inlets, manholes, outfalls, and roof drains. The Grounds department has launched a preventive maintenance program to manage these stormwater facilities.