Application of the SWMM Storage-Treatment Block For Analysis/Design of Extended-Detention Ponds

Thomas L. Newman II, P.E., Tarig A. Omer and Eugene D. Driscoll
HydroQual, Inc.

This paper describes the application of the Storage-Treatment (S-T) Block of the EPA Storm Water Management Model (SWMM) to design and/or analyze Extended-Detention Ponds (EDPs) for the reduction of pollutant loads from storm-water runoff. SWMM simulation results, supported with simple spreadsheet models, are presented to illustrate the influence of design features on expected pollutant removal efficiency of this popular best-management practice (BMP). Important insights on the operational characteristics of EDPs are also provided, based on sensitivity analyses that were performed to evaluate certain alternative design features in actual case studies. The importance of this refined method for EDP design is emphasized with examples of how the use of common rules of thumb or guidelines from BMP manuals could result in unexpectedly poor EDP performance.

Presented at:

International Conference on Stormwater and Urban Water Systems Modeling
Toronto, Ontario, Canada
February 18, 1999