Water Quality and Hydrologic Performance of Two Dry Detention Basins Receiving Highway Stormwater Runoff in the Piedmont Region of North Carolina

Abstract

Dry detention basins (DDBs) are a stormwater control measure (SCM) designed to provide flood storage, peak discharge abatement, and some water quality improvement through sedimentation; however, little data characterize DDB water quality performance in the highway environment. In this study, two DDBs [Hughes Farm Road and Poole Road basin (HFR and PRB henceforth)], constructed in 2010, mowed twice a year, receiving highway runoff, and located in the Piedmont of North Carolina (NC), USA, were monitored for up to 11 months. Flow-weighted composite samples were collected during storm events and analyzed for total phosphorus (TP); ortho-phosphorus (OP); ammonia (NH3); nitrate-nitrite (NOX); total Kjeldahl nitrogen (TKN); total suspended solids (TSS); and total Cd, Cu, Pb, and Zn. Influent runoff concentrations were similar to other studies in NC, and the monitoring revealed significant concentration reductions for most constituents in HFR. PRB significantly reduced concentrations for all pollutants except TSS, particulate phosphorous, and NH3, while significantly exporting Zn. HFR exhibited soil infiltration that led to significant pollutant load reductions (LRs) for all analytes except Cu. PRB exhibited little infiltration but had significant LRs for dissolved nutrients. This study provides evidence that DDB inlet and outlet configuration and the presence of standing water may impact DDB water quality improvement.