Case Study: Application of Best Practices for Pipeline Construction on Steep Slopes

Abstract In 2019, Coastal GasLink started the construction of the 670 km-long 48-inch gas pipeline across the province of British Columbia (BC) Canada. The project was constructed across varied terrain, including construction across two mountain ranges, the Rocky Mountains and the Coastal Mountain Range. The final 83 km of pipeline (Section 8) is characterized by an ascent through the Coastal Mountains to the highest point on the project at 1,428 m above sea level and a descent to sea level at the LNG Canada terminal in Kitimat, BC. Pipeline Section 8 contained a number of steep slopes (SS) ranging in angle from 15 degrees to 63 degrees. Many of these steep slopes had unique features, ranging from topography, geohazards, construction windows, accessibility, and weather-related factors. Each factor contributed to the selection process for the most suitable method of steep slope pipeline construction. The steep slope pipeline construction techniques which were used consisted of: i. Conventional open cut via trenching by blasting and mechanical excavation, a. Open cut using winch-supported equipment, b. Open cut with hydraulic sled using a top-down pipeline installation sequence, ii. Raise bore of an inaccessible steep slope (SS3), and iii. Cable cranes over a steep mountain side with slope lengths of up to 1,373 m and slopes angles up to 58 degrees. The raise bore and the cable crane construction techniques were a first in Canada for pipeline installation, providing innovative and unique solutions to pipeline construction. The objective of this case study is to provide an overview of the various steep slope pipeline construction techniques, provide a discussion on the challenges and successes for each technique with a summary of the lessons learned. A summary of the safety practices developed and implemented will also be presented.