Date: May 1992

Author(s): C. McIntyre, G. Aron, J. H. Willenbrock

On May 7, 1990, the Advisory Council to the Pennsylvania Housing Research Center authorized additional monies to be spent on further research in the area of storm water management focusing on alternative methods. The scope of this research effort documents the use of different design methodologies used to estimate storm water runoff and ultimately the sizing of detention basins in residential development.

SUMMARY OF RESULTS:

A comparison of the results of the three methods used in this study indicates that the maximum storage volumes are virtually identical for the Rational Method using Rawls or Aron coefficients and somewhat larger for SCS TR-55. However, past experience with basin response during storm events has indicated a failure of system performance for the more frequent storm events. Use of the Rational Method with Aron coefficients would decrease the size of the lower flow openings of basin outlet structures, thus providing truly functional facilities without additional cost.

The recommendations of this study can lead to an increase in basin performance which is the actual intent of detention-storage as addressed in storm water management ordinances. Other recommendations address safety measures which could be incorporated into basin design, thus reducing owner liability.

In September 1992, the Centre Region Planning Commission finalized a "Model Storm Water Management Ordinance for Municipalities in the Centre Region." The findings and recommendations of PHRC Report No. 8 were included in the revision of the ordinance and are now standard practice in design for all six municipalities in the Centre Region. As this information becomes more widely distributed, more regulatory agencies may adopt the recommendations of this report.