DEVELOPMENT OF DRY WEATHER FLOW DATA SELECTION CRITERIA FOR CITY OF DETROIT FLOW BALANCE ANALYSIS

Combined sewer flow data is being collected at a number of sites throughout the Detroit Water & Sewerage Department (DWSD) collection system. The collected data is being used to prepare an analysis to determine flows generated in various areas within the collection system. To establish data selection criteria, a regional sewer model was used to determine the time that would be required for the system to return to dry weather flow (DWF) conditions after specific wet weather events.As a result of model simulations, relationships were developed to represent time as a function of the rainfall amount of single- or multiple-day rainfall events. These relationships are a key component of the overall data selection for the flow balance, and provide an objective approach to characterizing DWF in the DWSD collection system.