Reinventing an Old Technology--Protecting Michigan's Surface Waters Through Maximizing Collection System Storage

Reinventing an Old Technology; Protecting Michigan's Surface Waters Through Maximizing Collection System Storage Submitted for Water Environment Federation 2022 Collection System Conference KEYWORDS CSO control, Real-time control, In-system storage, Research and Development PURPOSE AND BENEFITS The purpose of this paper is to communicate the benefits derived from optimizing an existing asset to further control overflows to surface waters and through that improve surface water quality. A secondary purpose is to demonstrate the process of reviving a dormant technology. SUMMARY The 8-1/2 Mile Relief Drain Drainage District is a sewer authority managed by the Macomb County Public Works Office (MCPWO). The District is located on the western shore of Lake St. Clair. With a surface area of 440 square miles, Lake St. Clair is one of the largest inland lakes in the United States, serves as an international border with Canada, and is a major recreational and economic asset to the metro Detroit area. In 1968, the District built and constructed a 12-foot diameter trunk sewer to convey combined sewage to a 28 million gallon retention treatment basin (RTB). The objective of these facilities was to convey combined sewage to a storage basin and control occurrences of combined sewer overflow from entering Lake St. Clair. During recent studies, it was learned that the 12-foot diameter sewer rarely filled more than a few feet. MCPWO inferred that utilizing the storage available in the sewer would further reduce the occurrences of overflows to the Lake. MCPWO subsequently retained Tetra Tech to lead a design project to develop a control system to utilize this storage within the existing infrastructure. Tetra Tech initially started the project by analyzing storage locations and potential devices. Two storage locations were subsequently selected. One being at the RTB influent pump station (Location B in figure provided in paper) and one being at a vacant right-of-way located approximately 2 miles upstream of the RTB (location A in the figure provided in the paper). DESIGN PROCESS Numerous storage devices were researched including pumps, gates, and inflatable dams. The selection of the storage devices underwent extensive evaluation focused on energy loss and impact on sewer customers, reliability, and available storage volume. Modifications to the existing wet well at the RTB pump station resulted in the ability to raise operating levels under some circumstances. This relatively inexpensive solution allowed for more storage to be utilized within the existing 8-1/2 Mile Relief Drain. An inflatable device was selected for the upstream site (referred to as the Beaconsfield site) depicted in the image below. A particular challenge was locating suppliers of inflatable dams. While this technology has been used internationally for several decades, the previous manufacturers were no longer offering this product. MCPWO worked with manufacturing personnel previously employed by these manufacturers to research and develop a product that would acceptably perform. This involved new manufacturers forming, new supply chains to develop, and new testing and manufacturing of the inflatable dam products similar to the example shown below. The two storage locations will be controlled by a network on instruments and programmable logic controllers to initiate the activation and deactivation of the storage devices. The reliability and networking of these devices were studied in great detail. RESULTS The proposed project was studied with a numerical model to analyze the expected impact on reducing overflows. The evaluation shows that the proposed design can add an additional 12 million gallons or more of storage to the system. This effectively increases the available storage from 28 MG to 40 MG (a 43% increase). This increased volume will reduce the annual occurrences of combined sewage overflow from approximately 7 to 5 events and reduce the volume of overflow from 265 million gallons to 212 million gallons or less (at least a 20% reduction). STATUS The project is designed and awaiting permitting by the Michigan Department of Energy, Great Lakes and Environment. The project is schedule to start construction in 2022 with a 2024 completion.