Riverview Siphon Improvements

A three-barrel inverted siphon, owned by the Metropolitan Council Environmental Services (MCES) in Saint Paul, Minnesota, experienced sanitary sewer overflows during the 1990's, prompting a study and improvements project to improve the facilities. The cast iron pipes were nearly 70 years old and the spills raised concerns over the capacity and condition of the pipes.A capacity study of the siphon system was included in a system-wide study in 2001, followed by a facility plan in 2003. The barrels were drained, televised and cleaned as part of the facility planning. Brown and Caldwell (BC) undertook final facility design to increase capacity and reliability as well as the functionality of the facility. Odors had long been a nuisance in the area of the inlet structure, or headbox, and were addressed. In addition, the barrels were interconnected to add redundancy to the facility.Capacity improvement was accomplished by installation of a fourth “landside” barrel, covering 2900' across the river flats prior to crossing the river itself. Rehabilitation of the headbox and tailbox were undertaken, as significant deterioration had occurred.Restoration and upgrading this facility proved to be a significantly complex in this congested urban setting. This paper will describe resolution of the many issues that arose during planning, design, and construction. Some of the challenges/aspects of the project that were addressed included open cut pipe installation adjacent to a live railroad, crossing through contaminated soils, an access shaft drilled through bedrock, elimination of an ineffective grit collection system, new odor control, construction of interconnects while maintaining siphon operation, cured in place pipe rehabilitation of both cast iron a cement lined steel pipe, hydraulic implications of a pump station connection directly into the siphon, construction adjacent to a flood levee and coordination with the Republican National Convention.