Control of Urban Runoff: The Role of Bioretention Systems

Increasing volumes of urban runoff have become a growing concern due to the effects of erosion on stormwater quality. In response, the usages of bioretention cells has greatly increased. The purpose of this investigation was to research the impacts of the bioretention cell at Charlottesville High School, to see if 1) bioretention performance decreases over time, 2) bioretention performance at the site meets specified Chesapeake Bay environmental quality standards, and 3) an enhanced bioretention cell at Venable Elementary School shows significant improvement compared to a traditional bioretention cell. In order to do this, we performed lab analyses on rain samples taken through robotic samplers at the inlet and outlet of the bioretention cell. Phosphorus and nitrate kits were used to determine nutrient concentrations, and samples were dried, filtered, and weighed for sediment concentrations. Using flow data collected from the samplers, the nitrate (N), phosphate (P), total nitrogen (TN), and total phosphorus (TP) mass loads were calculated for both the inlet and outlet. Percent removal was then calculated for all the nutrients and sediments in terms of mass and concentration. It was found that over time, the system had greater removal of nitrates and phosphates. Removal standards were met for sediments and phosphorus, but do not consistently meet nitrogen removal standards. The enhanced system performed better in nitrogen and phosphorus removal, but TN, TP, and sediment removal showed no significant improvement.

Author is also in the Department of Civil and Environmental Engineering.

Co-authors:

Perrin Falkner (Civil and Environmental Engineering),

Breanna Mariano (Civil and Environmental Engineering),

Emily Xu (Civil and Environmental Engineering),

Raleigh Heap (Chemical Engineering)