Wet Weather Water Quality Modeling

Abstract

An integrated, rainfall‐runoff and runoff‐receiving waterquality modeling protocol was developed to quantify the impact of combined sewer overflow events on in‐stream dissolved oxygen concentration. Modeling assumptions and input data requirements are consistent with intended usage as a planning and management tool. The modeling protocol was successfully calibrated and verified using data collected from several storm events occurring during the summer and fall of 1982. The expected frequency of in‐stream dissolved oxygen violation was determined from the analysis of historical records containing 208 combined sewer overflow events. 42% of these events resulted in minimum dissolved oxygen values below the 4.0 mg/L standard. Sludge deposit resuspension was demonstrated for a monitored high flow event when the in‐stream velocity was computed as 0.689 m/s (2.26 ft/sec).