ABSTRACT

Title of Thesis: FIELD EVALUATION OF HYDROLOGIC AND WATER QUALITY BENEFITS OF GRASS SWALES WITH CHECK DAMS FOR MANAGING HIGHWAY RUNOFF

Nor Eliea Eluziea Jamil, Master of Science, 2009

Thesis Directed By: Professor Allen P. Davis

Departrment of Civil and Environmental Engineering

Managing highway runoff is a complex storm water management problem. This research is an input/output field study that specifically examines the hydrologic and water quality benefits of having grass swales with an additional pre-treatment area and incorporation of check dams for managing highway runoff at a Maryland highway. These swales manage the hydrology of the stormwater by increasing the lag time (2-3 hours), reducing the overall average peak (32-44%) and reducing the total runoff volume (4-46%). The overall mass pollutant loads are reduced for TSS (38-62%), nitrate (92-95%), nitrite (54-71%), lead (78-82%), copper (56-70%) and zinc (67-79%). On the other hand, TKN (-120 to 44%), TP (-5 to 40%) and chloride (-61 to -4%) show mass increase. Compared to previous study, swales with check dams do not show any significant improvement over swales without check dams. However, a check dam swale with a pretreatment area has higher reduction of the overall mass pollutants removal for all pollutants except for TSS.