10.4122/1.1000001356 III, W. F. Hunt Sharkey, L. J. Smith, J.T. Lord, W.G. Jarrett, A.R. Hydrologic and water quality performance of four bioretention cells in Central North Carolina, USA DTU Library, Technical University of Denmark (DTU) 2005 Bioretention stormwater runoff hydrology nutrient removal runoff reduction soil media N.C. State University, Biological and Agricultural Engineering NC Cooperative Extension Pennsylvania State University, Agricultural and Biological Engineering en Conference full text 10.4122/1.1000001355 application/pdf 1 Two paired, field-scale bioretention studies (in Greensboro and Louisburg, NC, USA) have been conducted to study (1) hydrologic performance and (2) nutrient removal of phosphorus and nitrogen. In Greensboro, one cell was conventionally drained; the other contains a zone of internal water saturation (IWS) of 0.45m. They were continuously monitored from June, 2002, to December, 2004. During outflow events, TP concentrations were significantly lower (P<0.01) in the cell with an IWS zone, but these results were confounded by different phosphorus levels in each cell\342\200\231s fill soil. No significant difference existed among nitrogen removal. In Louisburg, both cells were conventionally drained and were comprised of low phosphorus fill soil. The bottom of one cell was lined with 20 mil plastic; the other was unlined. Estimates for exfiltration, outflow, and evapotranspiration were made by comparing each\342\200\231s cell\342\200\231s outflow and inflow. During the summer of 2004, approximately 25% of inflow exfiltrated the cell, another 25% left via the cell\342\200\231s underdrains and 50% of the inflow was released as ET. The importance of using low P-Index soil media for bioretention was reconfirmed, as average outflow concentration were 40-53% lower for TP and 25-60% lower for TN when compared to inflow concentrations for 9 storms.