Project Details

Secondary roads are the backbone of the nation’s rural transportation network. These transportation arteries carry small-to-moderate traffic flows from surrounding residential, farming, business and industrial land uses to principal county routes and primary highway systems. It is known that secondary roads are connected or interconnected to grassed strips and vegetated ditches on their right-of-ways, which functions as a natural best management practice for pollutant attenuation. Water quality benefits and the likely cost savings associated with the inherent and environmental-friendly vegetative treatment should be included in a comprehensive highway runoff management program.

This research has implemented a storm water monitoring program to characterize pollutant constituent concentrations and nutrient loading rates originated from roadway segments on three secondary roads in the Piedmont region of North Carolina. These secondary roads carry an average traffic volume of 590-2,600 vehicles per day in both directions. Hydrologic and water quality data were collected for 26-30 storm events from two paired sites at each of the three monitoring locations. The paired-site monitoring strategy has provided a common database to evaluate the effectiveness of existing roadside vegetation for the attenuation of pollutant constituents in secondary roadway runoff.