The Association of Consulting Engineering Companies of British Columbia recently presented Tetra Tech with the Award of Excellence in Municipal & Civil Infrastructure for the Mosquito Creek Debris Flood Barrier project. The Awards for Engineering Excellence Gala was held in Vancouver, BC, on April 12, 2014.

North Vancouver’s Mosquito Creek drains Grouse and Fromme Mountains through a densely populated area. The upper part of the watershed contains a number of existing and potential landslide areas and log jams with sediment wedges that could trigger a debris flood.

The District of North Vancouver retained Tetra Tech as the prime consultant tasked with the design and installation of a barrier on Mosquito Creek that would protect the nearby residential areas. This project demonstrates engineering excellence in many ways.

Our work included the following:

• Geohazard inventory map specific to Mosquito Creek that explained the magnitude of debris floods
• Barrier location that provided the most effective protection (volume and impact forces), minimal construction in a fish bearing creek with endangered species and low impact to riparian zone, cost of construction, aesthetics, access, and maintenance
• Flexible barrier that absorbs the impact of woody debris, retaining it while letting water pass, and is highly cost-effective and efficient compared to a concrete barrier
• Series of high-tensioned anchors that secure the net, which required rock mass modelling to prevent heave, and installation of thirty completely hidden long dowels to reinforce the rock
• Recessed anchor heads that ensure that only the net will need to be replaced if a debris flow occurs
• Net that can be released remotely by a unique, world-first design
• Roped-access, minimal-impact construction methods

This low cost, less intrusive solution is now the first line of defence in protecting the public from debris floods in Mosquito Creek.

We congratulate the project team whose hard work and technical innovation made this project a success.