99 Avenue Sanitary Trunk Rehabilitation - Stage 2

Abstract

The 99 Avenue Sanitary Trunk Rehabilitation project is a two-stage project to rehabilitate approximately 1.1 km of monolithic concrete arch-shaped sanitary trunk sewer located about 30 m below ground in Edmonton, Alberta. Stage 1 involved the construction of a ~1.6 km bypass sewer to divert flow, facilitating the Stage 2 trunk rehabilitation, which was completed in 2023 (NASTT 2023 No-Dig North Paper MM-T4-03). Stage 2 was awarded to Shanghai Construction Group (Canada) Corporation (SCG) as a design-build contract. SCG’s rehabilitation approach involved sliplining discrete segments of 950 mm span by 1400 mm rise non-circular fiberglass liner into the existing host tunnel (approximately 1200 mm span by 2000 mm rise) via worker-entry. Key challenges of the project included restricted access, which required the construction of deep working shafts; a complex upstream sewer network with high flow volumes that had to be diverted for isolation; difficulties in cleaning and inspecting the trunk; uncertain short-term structural conditions for safe worker-entry; variable deflections in the host tunnel alignment; poor invert conditions affecting liner insertion; and significant groundwater infiltration that required careful management during the annular space backfill grouting. This paper will examine the project's constraints and challenges, the rehabilitation planning and execution, the design-build team's innovations, and the lessons learned, along with recommendations for future projects.