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Coldwater Wet Weather Storage Facility Tank "A"
Metropolitan St. Louis Sewer District

St. Louis, Missouri

CMT served as the prime consultant for both the pre-design study and for the final design of the Coldwater Wet Weather Storage Facility Tank "A" project for the Metropolitan St. Louis Sewer District (MSD). The project included hydraulic modeling to determine the best alternative to eliminate sanitary sewer overflows (SSOs) and basement back-ups in an area served by a 9.4-mile-long section of the Coldwater Creek trunk sewer. CMT developed a flow equalization/storage tank solution that proved to be a more optimal strategy and resulted in a cost savings of over $80 million over a traditional deep tunnel relief sewer.

The main features include a 6 million gallon concrete wet weather storage tank, a diversion structure, an influent pump station with six submersible pumps to accommodate a wide range of flows with a firm capacity of 30,000 GPM, and a SCADA system for real-time monitoring of wet weather levels in the trunk sewer and controlling the diversion of flow into and out of the wet weather storage tank.

A context sensitive design approach was essential given the location of the tank facility within a residential community. CMT and MSD worked with a citizens' committee to address concerns that the facilities would be obtrusive and unsightly. An Exterior Insulation Finishing System was used to create faux windows and other aesthetic features on the tank surface to make it resemble an office building. Green features were incorporated including a unique rain water harvesting design for the tank's spray wash system. A rain garden was also designed for on-site groundwater infiltration.