Long Term Performance of Water Quality Ponds

A report developed under EPA's Nationwide Urban Runoff Program (NURP) describes an analysis methodology and presents graphs and example computations to guide planning level evaluations and design decisions on two techniques for urban runoff quality control. This presentation provides a condensed summary of the analysis methodology, and an overview of the performance that can be expected from stormwater detention basins. The equations involved are solved for the range of values the controlling parameters can assume. Pertinent results are presented in a series of graphs which are then used to illustrate the general relationship between design size and performance. The presentation also includes a discussion of several issues relating to water quality ponds, including data on storm runoff settling velocities, the effect on the analysis of small storms that do not produce runoff, and use of the analysis method to size sediment forebays.