Wet Detention Pond Design and Operation

Dr. David Yonge

Three highway runoff wet ponds were studied over an 18-month period. Pond location covered a range of weather patterns and traffic densities, resulting in the collection of inlet and outlet water quality data that was representative of a range of conditions. Two ponds were located in Washington (Vancouver and Spokane) and the third pond was located in Shreveport, Louisiana. The Shreveport pond was operated as a "zero discharge" pond for most of the year and was emptied when it became full. The culmination of data collection and interpretation was the development of a decision support system (DSS) that can be used to design a wet pond or estimate the performance of an existing pond which is presented in a users manual that is separate from this dissertation.

The inlet, and outlet, of each wet pond was characterized with regard to chemical (dissolved and total metals, PAH, TPH, nutrients, and pH), physical (suspended solids, flow and temperature) constituents over the duration of the study period. Influent and effluent toxicity was also evaluated during selected storm events. In addition, chemical and physical data were collected on pond water column and pond sediment samples. These data indicated that wet detention ponds can be effective at contaminant retention for a variety of constituents, with the majority of contaminant removal associated with sedimentation. Contaminant removal and retention, however, is dependent upon pond hydraulic characteristics and constituent type.