Capilano–Seymour Water Tunnel Surveying & 3D Scanning

Project Snapshot

Project Overview

Introduction

Underhill contributed advanced survey support to the construction of two 7.4 km water tunnels connecting Capilano Reservoir with the Seymour filtration plant—part of Metro Vancouver’s critical water infrastructure upgrade. The project demanded precision from start to finish, involving multiple contractors and complex underground operations.

Project Challenges

The tunnels required sub-centimeter accuracy over long distances and in challenging underground conditions. Multiple phases, including alignment, QA/QC, and as-built verification, needed to meet stringent tolerances to ensure functionality and safety of the water delivery system.

Underhill’s Approach

Initially contracted by Bilfinger Berger Canada, Underhill conducted a check survey of the GVRD’s GPS control network. We later established azimuth baselines for gyrotheodolite calibration, and conducted a plumbing check survey on the 180 m Seymour shaft—confirming alignment within millimetres.

As the project progressed, we provided quality control of the contractor’s survey work, ran precise double-run control surveys through both tunnels, and created 200+ as-built cross-sections using the Trimble GX 3D Scanner. Point cloud data was processed using Trimble Realworks Survey Advanced, enabling direct comparison with tunnel design specifications. We also performed 1 mm–tolerance as-built surveys on 3 m pipes prior to installation.

Notable Outcomes

• Verified 180 m shaft plumbing to within millimetres 
• Ran double-run control survey through 8 km of tunnel 
• Generated over 200 3D cross-sections from point cloud data 
• Provided as-built QA on 3 m diameter pipe installations with 1 mm precision 
• Supported accurate and secure delivery of major water infrastructure 

Technical Highlights

• Surveyed twin 7.4 km bored tunnels using double-run control 
• Conducted 3D laser scanning with Trimble GX for cross-section extraction 
• Verified alignment and plumbing of vertical shafts 
• Calibrated gyrotheodolite baselines for underground navigation 
• Processed and overlaid point cloud data in Realworks Survey Advanced 6.2.0 
• Provided QA/QC and final as-built documentation with high-precision tolerances 

Project Impact

Underhill’s high-precision surveys ensured the safe, accurate construction of twin tunnels vital to Metro Vancouver’s drinking water supply. Our work verified shaft alignment, controlled tunnel accuracy over kilometres, and delivered as-built data with millimetre precision. This contributed to the long-term reliability and resilience of one of the region’s most critical infrastructure upgrades.