PRACTICAL APPLICATION OF THE “C” IN CMOM – DYNAMIC HYDRAULIC MODELING REVEALS CHALLENGES TO PREVENTING OVERFLOWS

As the “C” in the emerging CMOM regulations refers to Capacity Assurance of a collection system, many communities are taking necessary steps to make decisions on how to better operate their collection system facilities. In particular, USEPA recommends the use of continuous infiltration and inflow (I/I) models, coupled with hydraulic models to perform capacity analyses of critical facilities. Understanding this component was a decisive goal for the Western Lake Superior Sanitation District (WLSSD) when they undertook a study aimed to identify and evaluate options to avoid overflows within a hydraulically strained portion of their collection system.Historical overflows at pump stations and manholes within this portion of WLSSD's service area had been documented and were a serious concern. WLSSD took action to gain a better understanding of the collection system through development of hydrologic and dynamic hydraulic computer models. These models aided in a sound technical evaluation of the collection system and provided new insight to the existing system capacity, I/I conditions, the impacts of adding new development flows, and options for reducing and/or avoiding potential overflows.This paper presents an overview of CMOM regulations as they pertain to system analysis, the techniques and data used in constructing and analyzing the computer models and model results, and the alternatives evaluated for improving the performance of the WLSSD's East Service Area collection system. Specific attention is paid to development and evaluation of the alternatives to reduce and/or avoid overflows through use of the dynamic computer models.