Burbrook Trunk Storm Sewer Project

This three-phase project would create a large-diameter trunk storm sewer to eliminate the combined sewer in place. The undersized combined sewers were surcharging for 1-year storm events resulting in sewer backups and basement flooding for over 350 properties. The first two phases were successfully completed, however, the third phase, which included two crossings under the Canadian National (CN) railway, had major issues. At the time, the contract documents allowed for an open-face style tunnel boring machine (TBM) in combination with dewatering. A high water table and sandy soils provided very unstable conditions. During the longer bore under the tracks, settlement in the ground occurred such that both the City of London and CN officials agreed to cease construction, pull the TBM out, restore the site and reanalyze. For over a decade, the city worked with engineering and consulting firms to evaluate other tunneling methods. During this time, the microtunneling industry and technologies in North America advanced significantly which led the team to conclude that microtunneling would be the best suited tunnel technology for this project. 

It took 5 days to complete the tunneling under two crossings; a 50m crossing under two sets of railway tracks and a 175m crossing under two high-speed railway tracks and a rail yard. There were strict settlement criteria in place on the rail infrastructure, alerts at 8mm and complete shutdown at 15mm. Both crossings were completed using 2,500mm ID (3,000mm OD) microtunneling pipe from DECAST. At the time, this was the largest diameter microtunneling project in Ontario. This project was completed on time, under budget and met all of the project objectives.

REF: https://www.wardandburke.com/project/burbrook-trunk-sewer-ontario/