Peaking Into the Future: A New Methodology for Sizing Peak Flow Storage - Trinity River Authority of Texas Develops Innovative New Approach

As more stringent requirements to eliminate Sanitary Sewer Overflows (SSOs) are enforced, peak flow management becomes a more challenging task for wastewater treatment managers. The simplest approach to peak wet weather flow management, from a regulatory point of view, is onsite storage, where excess influent flows are diverted to side-stream storage basins to prevent the washout and long-term effects on biological processes. In the past, methods of sizing peak flow storage ranged from using a 5-year 24-hour storm hydrograph, to developing longer periods of wet weather events and calculating the resulting flows due to back-to-back storm events. This new methodology is intended to identify a storage volume that balances construction costs with the level of risk for potential storm events. It allows a utility to evaluate storm event coverage against the cost to build storage.