CASE STUDIES
Silverhope Creek Microtunnel
Crossing Beneath an Archaeological Site
DESCRIPTION
The Tunneling Company completed the Silverhope Creek Microtunnel 4 km from Hope, B.C., as a way to safely cross beneath the Hope Archaeological Site. The Tunneling Company excavated a launch shaft for the microtunnel with a 12 m outer diameter and a depth of 13.3 m. The launch shaft was built using secant pile construction, with the piles installed at a depth of 16.3 m. The reception trench for the Microtunnel Bore Machine (MTBM) was built by the general contractor, who used a slide rail shoring system at a depth of 4.1 m.
CHALLENGES
The archaeological site was located directly across from the entry shaft, making it critical that drilling product did not reach the ground and risk contaminating the zone in question. The Tunneling Company constantly monitored the microtunnel’s progress, with the vertical tunnel alignment having a greater depth at the location to reduce the risk of surface release or frac out of the face slurry. In order to bring the Microtunnel Boring Machine (MTBM) to the reception shaft location, the alignment progressed through a 700m radius curve and a steep inclined exit of 11 degrees
Abrasive ground conditions also posed a challenge, causing high wear on equipment and components. To mitigate any associated risks, crews frequently paused tunneling, allowing them to repair and replace hoses and pumps as needed.
OUTCOMES
Despite challenging conditions and the need for strict alignment control, The Tunneling Company’s experienced site crews completed the project to the required tolerances, specifications and quality. This undertaking allowed the client to install the product pipe without issue — all while ensuring that an important archaeological site remained undisturbed.
