Dense Urban Area Sewer Replacement - A Jack and Bore Success Story

A housing authority was experiencing issues with the existing 12-inch gravity sewer which collected sewage from the apartment buildings and nearby community center. The existing gravity sewer travelled through a section of land which was part of a landfill which had been abandoned in the 1970s. This sewer had been overburdened with solid waste from the landfill, was in poor condition, and was scheduled for replacement. Due to the safety concerns surrounding the landfill and the complications of re-opening the closed landfill, the existing sewer could not be rehabilitated and a replacement sewer could not be installed in parallel, so a replacement sewer was required along an alternative alignment. This presentation highlights the design challenges and solutions associated with the replacement sewer alignment, the selection and benefits of the Guided Boring Method (GBM) for installation, and the results of the completed installation.Due to the large depth of the replacement sewer, and the proximity of the sewer to buildings and existing utilities, a conventional open trench installation was not appropriate. Various Jack and Bore trenchless technologies were reviewed and the GBM was determined to be the most applicable to the conditions and constraints of the project. Other key engineering design aspects of the project included specifying the carrier and casing pipes, locating launching and receiving pits, tie-in at the upstream and downstream location, relocation of existing utilities at boring machine pits, overhead utilities, traffic control during construction, and abandonment of the existing sewer once construction of the replacement sewer was complete.The end result of the project was a new gravity sewer which met the needs of the housing authority, which was installed with minimum disruption to nearby residents, no adverse effects to the environment, minimal disturbance to existing utilities, and reduced total construction costs due to the use of proper installation techniques and practices.