Project Snapshot
| Category | Details |
| Client | BC Rail (as part of the Northeast Coal Development Project) |
| Project Name | Tumbler Ridge Railway & Tunnel Construction Survey |
| Location | Northeast BC (near Tumbler Ridge, ~250 km NE of Prince George) |
| Date | 1980–1983 |
Project Overview
Introduction
From 1980 to 1983, Underhill served as the lead consulting surveyors for the construction of 140 km of railway through BC’s Rocky Mountains. This line formed a critical part of the province’s Northeast Coal Development Plan, requiring advanced surveying techniques across extremely rugged terrain.
Surveying Through the Rockies
Underhill’s work began with the location of the railway centreline, enabling right-of-way clearing and later, detailed construction surveying. Teams navigated steep slopes and remote access, managing the layout and monitoring of some of the most complex sections of the route.
- Supplied up to seven field crews for key tunnel approaches
- Managed four tunnels, 15 bridges, and 8 km of grade
- Used Kern DKM3 0.5″ theodolites and EDM for high-precision control
- Ran surface control networks across two mountain ranges
Tunnel Control & Breakthrough Accuracy
The project included the 9.7 km Table Tunnel and the 5.6 km Wolverine Tunnel, each requiring precise geodetic control for accurate headings and breakthroughs.
- Breakthrough error (Wolverine Tunnel): 50 mm lateral / 50 mm vertical
- Breakthrough error (Table Tunnel): 87 mm lateral / 37 mm vertical
- Elevations were calculated using simultaneous reciprocal vertical angles, due to terrain limits on conventional leveling
- Final adjustments used least-squares analysis on provincial mainframe systems
Innovations & Quality Control
BC Rail brought in George B. Miller, BCLS for independent check surveys, including one of the first uses of a Gyromat gyrotheodolite in Canada for azimuth validation. Though the gyro data proved inconsistent, it marked a notable attempt at integrating early precision orientation tech into Canadian tunnel projects.
In 1987, Carl Friesen’s thesis at the University of Calgary reviewed the control network accuracy and found it outperformed predictive models—highlighting the exceptional performance of experienced field crews and the conservative nature of standard instrument specs.
Project Impact
- Enabled the completion of 140 km of mountain railway under extreme conditions
- Supported the engineering of tunnels, bridges, and complex grade work
- Demonstrated high-accuracy surveying in geologically and logistically difficult terrain
- Set early precedents for GPS-assisted control and digital computations in major infrastructure
