The Raleigh-Durham Airport Authority recently received state approval to proceed with construction of a sustainable stormwater management system, the largest of its kind in North Carolina. The innovative submerged gravel wetland system will be built to treat stormwater from the Park Economy 3 Expansion (PE3) project and is expected to be more effective than traditional stormwater management systems in removing pollutants from stormwater runoff.
In collaboration with North Carolina State University, submerged gravel wetlands were designed to treat stormwater associated with the project. A submerged gravel wetland uses plants to treat runoff in an above-ground wetland through a biochemical process. Below-ground internal storage will have gravel layers that maintain constant water levels for the plants and provide processes to treat water.
The submerged gravel wetlands are expected to remove more sediment and nutrients from stormwater than other control measures such as dry ponds. All the water that is discharged from the basins will be analyzed for treatment values and the results will be provided to staff permitting officials. The submerged gravel wetlands will be designed to exceed state requirements for stormwater treatment. They will treat more than one inch of runoff, improve nutrient treatment, be designed for at least a 50-year storm event, and temporarily hold enough water to prevent flooding during a 100-year storm event.
The Airport Authority received the stormwater management permit from the N.C. Department of Environmental Quality on June 26 allowing construction to begin. The Airport Authority is pursuing Envision verification for the Park Economy 3 Expansion Project, which will add approximately 8,700 additional spaces to the existing surface lot. Envision is a framework that provides direction in the planning, design and construction of sustainable and resilient civil infrastructure. The criteria and performance objectives available within the Envision framework promote sustainable choices throughout a project’s lifecycle, including in the operations and maintenance of the infrastructure.