Arch Engineers Ltd. provided expert design and engineering services for over 250 trenchless crossings on the TransMountain and Coastal GasLink projects. These crossings supported major pipeline infrastructure, ensuring safe and efficient pipeline installation beneath sensitive and high-traffic areas such as highways, railways, steep slopes, boulder fields, and marshlands.
Our scope encompassed geotechnical analysis, structural design, and shoring systems for entry and exit pits. This included solutions for HDD (Horizontal Directional Drilling), TBM (Tunnel Boring Machine), and casing removal operations. Many pits exceeded depths of 8.5 meters and required complex designs to accommodate large-scale equipment such as thruster machines and HDD units. For instance, at the Clearwater River crossing, boulders damaged sheet piles, causing gaps and deformation. Arch Engineers adapted with patch welding, additional walers, struts, and a soldier pile design to stabilize excavations and allow progress.
Moreover, dynamic site conditions and client-driven changes required rapid iteration. Some pits underwent over eight design revisions. On one site, conflicting engineering approaches from adjacent contractors led to instability. Arch intervened by issuing a stop work order and designing a trench box system that stabilized the working area and enabled safe pipe hammering to resume. Additional designs included an aqua dam sheet pile wall for in-water isolation, along with alternative containment methods such as sandbags and lock-blocks.
Throughout the projects, Arch Engineers demonstrated unparalleled flexibility, innovation, and a strong commitment to safety. By delivering practical, tailored solutions under extreme time pressures, Arch successfully navigated complex geologies and operational challenges, ensuring safe, efficient, and compliant pipeline installation through trenchless crossing methods.