EXAMINATION OF THE EFFECTIVENESS OF BIORETENTION CELLS AND POROUS PAVING PRACTICES IN AIKEN, SC

This work seeks to quantify the impact and effectiveness of green infrastructure practices, specifically bioretention cells and porous asphalts, for the reduction of peak flow and volume of stormwater that discharges into the headwaters of the Sand River watershed in Aiken, SC. Stormwater runoff flows and volumes were monitored in the upper Sand River watershed that includes the urban Aiken area, along with two nested subwatersheds, prior to, during, and after the construction of the bioretention cells and porous asphalt sites. Flow data from these monitoring stations were analyzed and the data suggested that there was no significant reduction in volume of stormwater exiting the Sand River watershed. However, there was a significant reduction in the volume of stormwater exiting the subwatershed with a bioretention cell under wet conditions, and there was also a significant reduction in the volume of runoff for the control subwatershed under dry and wet conditions. Selected bioretention cells and porous asphalt sites were monitored to determine their as-built performance compared to their designed performance. One bioretention cell located along Park Avenue between Chesterfield Street and Newberry Street (PCN) was extensively monitored and analyzed. All of the monitored bioretention cells and porous asphalt sites functioned as designed although the data suggested that the bioretention cells were slightly over-designed. The porous asphalt sites were effective at capturing localized surface runoff and either infiltrating it back into the native subsoil or routing it into the bioretention cells. STELLA¨ modeling software was successfully used to model and characterize the water budget and hydraulic performance for two bioretention cells. Based on the results of this study, while the green infrastructure retrofits investigated did function to reduce stormwater peak flow and volume, the limited size and area of the retrofitted practices did not significantly impact the peak flow and volume exiting the entire watershed. However, further construction will likely have a more significant impact, because the as-built stormwater control measures are functioning as designed