A bioretention cell in Raleigh, NC significantly reduced the concentrations of fecal coliform and E. coli in stormwater. Efficiency ratios were 0.69 for fecal coliform and 0.71 for E. coli.
Hunt, William F., J. T. Smith, S. J. Jadlocki, J. M. Hathaway, and P. R. Eubanks. (2008). Pollutant removal and peak flow mitigation by a bioretention cell in urban Charlotte, NC. Journal of Environmental Engineering.