Many communities across the U.S. are prioritizing investments in their aging infrastructure, including their sewer systems. Aging sewers often contribute to overflows, which can become a public health hazard. Over the past several years, the city of Springfield, Illinois, has focused its efforts and funding on updating and rehabilitating its sewer system, particularly in the northeast part of the city.
The city of Springfield’s Office of Public Works identified the Cook Street Sewer District as a project that would require a phased approach to upgrading its aging sewer system. The Cook Street Sewer District collects stormwater and wastewater in a combined system of pipes, manholes and inlets from residential neighborhoods surrounded by four thoroughfares that serve a mix of commercial and residential properties.
The Cook Street project is a continuation of sewer and manhole rehabilitation projects in Springfield. The majority of the city’s central business district and the near-east sewers are more than 100 years old and need replacement or rehabilitation to serve the city for the next century.
The combined system predominately comprises brick mains and manholes. The brick portions of the system were missing mortar, with some segments or structures experiencing greater degradation than others. Missing mortar causes the infiltration of not only water but debris and bricks, which can lead to the structural failure of a pipe or manhole. In some cases, this can also result in a cave-in, requiring emergency maintenance by the city.
Hanson provided phases 1 and 2 design services and phase 2 construction observation for the project, which extended from Cook Street to Martin Luther King Jr. Drive to South Grand Avenue to 11th Street.
The existing combined system was under the city streets. The location beneath the pavement provided easy access to the combined system; however, the roadway also housed other utilities, which were a constant hurdle during the removal and replacement within the thoroughfares. During phase 1, lead water services under 11th Street required special attention during construction. During phase 2, proposed manholes that were to be placed at T-intersections of the combined system had to shift because of utilities. In addition, new pipes had to be placed to correct the alignment to the new manhole.
Phase 1 involved using conventional construction methods for the removal and replacement of combined storm and sanitary sewer mains for a portion of the project area covered by the two phases. Phase 1 included only the portion of the system on two streets within the neighborhoods — 11th and 12th streets. Along 11th, the combined system’s main and manholes were removed and replaced from the north and south areas of the project, and along 12th, two pipe segments and adjoining manholes were removed.
Phase 2 focused on improving the aging system with trenchless technology methods, such as cured-in-place pipe, cementitious linings and epoxy coatings. Items beyond repair by trenchless technology were repaired with traditional open-cut removal and replacement.
Traditional construction methods also were used to make significant system maintenance improvements, such as adding manholes at T-intersections. This important improvement allows city crews to access the combined system for cleaning, maintenance and inspection.
Sewer Engineer Vince Smith, P.E., of the Sewer Division of the Springfield Office of Public Works, said the prior poor condition of the brick sewers left the city hesitant to attempt debris removal out of a fear of the sewer collapsing. He added that the linings in the rehabilitated sewers have vastly improved the flow within the mains.
“Now, we can more quickly determine the source of reported backups,” Smith said. “Before the project, it was sometimes difficult to tell what was really happening due to debris and defects in the main holding up the flow, and some areas were not accessible because of the debris or lack of manhole access. Now, we have an accurate map of all the public sewers in the area, and we have had zero issues with backups in the segments that were lined or replaced.”
The construction of this project progressed during the COVID-19 pandemic in 2020. As part of its safety program, the contractor added a rear-facing monitor to its television truck to allow a construction observer to watch construction activities via closed-circuit TV without accessing the confined workspace in the TV truck.
As part of the contract documents, the contractors were required to submit their company safety plans to the city of Springfield and submit a material safety data sheet with products and confined space plans to the Springfield Fire Department.