13. Type of Report and Period Covered

Nonpoint source pollution is an environmental problem that is a concern among regulatory agencies and water quality professionals. A portion of this pollution is conveyed to receiving waters by stormwater drainage from highways, often via vegetated roadside shoulders, also called borrow ditches. The vegetated shoulders may act as filter strips, reducing the concentrations of pollutants in highway runoff. Vegetated filter strips are recognized by many regulatory agencies as a Best Management Practice for the control and treatment of stormwater; however the relationship between performance and design parameters such as length, width, and vegetative cover are not well understood. Therefore, it is important to evaluate and document the extent to which these vegetated areas may reduce pollutant loads in runoff and mitigate the effects of discharging untreated highway runoff directly into receiving bodies of water. The primary objective of this study is the documentation of the stormwater quality benefits of these vegetated sideslopes typical of common rural highway cross sections in Texas. The scope of this project included the selection of six sampling sites in the Austin and College Statio