I performed a field-scale assessment of the water quality and hydrology of a conventionally-designed bioretention cell over two periods, 4 years apart. In this study, we found that high hydrologic and contaminant mass removal was maintained over the life of the bioretention cell, but that concentration data at the bioretention underdrain revealed poor to moderate treatment performance. If we wanted to improve the removal of dissolved pollutant concentrations in the outlet, we would require more targeted design such as media amendments or hydraulic controls. There were differences in treatment performance between the two monitoring periods, mainly due to the settling of bioretention media, showing that monitoring more than 2 years a post-construction will give a more reliable treatment performance evaluation.
A manuscript for this project was submitted for journal publication and is currently undergoing review.