Environmentally Sensitive Road Maintenance Practices: Sediment Reduction with Use of Driving Surface Aggregate

The objective of this study was to quantify sediment generation rates from unpaved roads before and after placement of a durable unbound surface aggregate. Sediment pollution from unpaved roads is a well-documented problem across the United States and the world. The quality of road surface material is a large determining factor in how much sediment is generated from the road surface during rain events. This study attempted to quantify the sediment reduction potential of driving surface aggregate (DSA), an unbound aggregate specification used in Pennsylvania that was designed specifically as a wearing course for gravel roads. DSA is widely used to surface roads in Pennsylvania to reduce road runoff in environmentally sensitive areas. The road surface erosion rates in this study were measured on two sites before DSA placement and at time intervals of 1 month, 1 year, and 2 years after placement. A rainfall simulator was employed to generate a consistent and repeatable storm event over a 100-ft (30-m) section of road for this study. Results show that compared with the existing mixed-surface roadway, DSA placement reduced total sediment runoff by 75% after 1 month, 90% after 1 year, and 96% after 2 years for the two sites tested.