Eagle Mountain TBMs complete 8.9km Canadian pipeline tunnel

TBM excavation has been completed on FortisBC’s 8.86km Eagle Mountain – Woodfibre Gas Pipeline tunnel in British Columbia, Canada, following breakthrough of the hard-rock drive into the previously completed soft-ground section. The tunnel, being constructed by the Frontier-Kemper Michels (FKM) JV, runs beneath Monmouth Mountain and the environmentally sensitive Skwelwil’em Squamish Estuary between Squamish and the Woodfibre LNG site. Two TBMs were used to tackle the sharply contrasting geology along the alignment. A Herrenknecht Mixshield excavated approximately 3.8km of soft ground from the BC Rail site in Squamish, while a 4.53m-diameter gripper TBM drove approximately 5km through predominantly granitic rock from the Woodfibre end. The two drives met at an underground interface chamber. The approximately 4.1m-diameter Mixshield was launched from a shallow portal and excavated beneath the Skwelwil’em Squamish Estuary through river sediments including sand, silt and gravel. It installed a precast concrete segmental lining as it advanced, with pressurised slurry used for face support and spoil transport. At the opposite end, the hard-rock TBM was launched from the Woodfibre site following excavation of a 25m starter tunnel by drill-and-blast. Its approximately 5,036m drive passed beneath Monmouth Mountain through predominantly granite, granodiorite and quartz diorite, with rock cover reaching around 420m beneath Monmouth Ridge. The completed tunnel descends from around 50m above sea level to approximately 25m below sea level at its lowest point. FortisBC selected the underground alignment to avoid surface disturbance within the 673ha Skwelwil’em Squamish Estuary Wildlife Management Area. “This tunnel breakthrough is a proud moment for us,” said EGP tunnel senior project manager Ignacio Calvo González. “After years of planning, seeing the two tunnel sections connect is incredibly rewarding.” With excavation complete, crews will remove the TBM and prepare the tunnel for pipeline installation. Two parallel NPS 24, 610mm OD high-pressure natural gas pipelines are to be installed through the tunnel, with excavated rock subsequently used as protective backfill. The tunnel forms a key element of FortisBC’s wider Eagle Mountain – Woodfibre Gas Pipeline project, which involves around 50km of new gas pipeline between Coquitlam and Squamish to supply the Woodfibre LNG facility. Construction in the Squamish area began in August 2023 and tunnelling started in spring 2024. Completion of the overall EGP project is scheduled for 2027. Comments: