ASCE has honored the writing team of L. L. Willard; Tess Wynn Thompson, Ph.D., A.M.ASCE; Leigh-Anne Krometis, Ph.D.; T. P. Neher; and Brian D. Badgley, Ph.D., with the 2019 Wesley W. Horner Award for the paper “Does It Pay to Be Mature? Evaluation of Bioretention Cell Performance Seven Years Postconstruction,” published in the September 2017 issue of Journal of Environmental Engineering.
In this nominated work, researchers examine long-term effectiveness of bioretention cells (BRCs). The project evaluated the performance of a BRC after seven years to determine reductions in flow rate, flow volume, suspended solids, nitrogen, phosphorus, and fecal indicator bacteria (FIB). These observations were compared with analyses conducted immediately postconstruction. Inflow and outflow water samples were collected for sediment, nutrients, and FIB. Soil media samples were collected from multiple depths and analyzed for denitrifying bacteria.
Results indicate that the BRC remains effective at reducing storm flows, nutrients, and FIB. These reductions were correlated to outflow volume rather than storm characteristics. The majority of denitrifying bacteria were present in the top media layers, despite the presence of an internal water storage layer for denitrification. This finding suggests that denitrification primarily occurs at anoxic microsites in the upper layers and that a lack of carbon at deeper depths may limit significant microbial growth.
The Wesley W. Horner Award recognizes papers that have contributed to the areas of hydrology, urban drainage, or sewerage.