Post-Construction Runoff Program
The development of the natural landscapes into impervious surfaces such as roof tops, roads, driveways and sidewalks results in increased stormwater runoff and increased amounts of pollutants entering our streams. Because of this increase, most new or redevelopment projects are required to implement post- construction stormwater controls. These controls are designed to reduce potential pollution and hydrological impacts to downstream surface waters. Post-construction stormwater may be addressed with stormwater control measures to treat the runoff, or through site design that employs low impact development (LID) or green infrastructure (GI) principles in order to reduce the volume of runoff.
NCDOT’s Post-Construction Runoff Control Program is designed to help protect the quality of our surface waters across the state. The NCDOT Stormwater Toolbox Manual helps stormwater engineers select, design, and maintain stormwater controls that are appropriate given site conditions and the identified pollutants.
In response to the identification of excess nutrients as a pollutant in the Falls Lake and Jordan Lake watersheds (of which Little Alamance Creek is a part of), NCDOT has initiated the Guided Reduction of Excess Environmental Nutrients (GREEN) program. The GREEN program integrates and enhances NCDOT’s stormwater and nutrient management practices in both Falls Lake and Jordan Lake watersheds.
The goal of post-construction runoff pollution controls is to limit the generation and transport of pollutants associated with built-upon areas and how they are used. This goal is achieved through the administration of programs that include the regulatory requirement for post-construction runoff stormwater control measures, review of development and redevelopment plans, reliance on regulatory measures for abatement and enforcement, and annual inspection and reporting. For the Cities of Burlington and Graham, development that cumulatively disturbs greater than one acre is required to comply with standards that limit the developments impact on downstream water quality. These requirements are why many newly developed communities and properties have structural stormwater control measures like water quality ponds, bio-retention basins, and stormwater wetlands. Structural stormwater control measures (also called SCM’s) can be installed with new development or as “retrofits” and are covered in depth under our stormwater retrofit page.
The project partners have been managing post-construction runoff over the tenure of their NPDES MS4 permits. Given the limited remaining development potential of the watershed, it is anticipated that these pollution controls will have a minor but positive impact going forward in addressing existing stressors in Little Alamance Creek watershed but will help prevent exacerbating the current level of impairment. These pollution controls could play a more significant role in pollutant reduction where redevelopment is significant enough to trigger regulation.