BC Hydro, Dawson Creek, BC
BC Hydro faced the challenge of installing 240 tower foundations over 73 linear kilometres of diverse and consistently difficult terrain from Dawson Creek to Chetwynd. These towers consisted of 170 monopoles and 70 lattice towers, all designed to accommodate differing geotechnical conditions over the length of the project.
The Almita engineering team worked closely with the BC Hyrdro engineering team to develop foundations that could meet the changing geotechnical conditions as well as the different tower types selected for the project. We partnered with Deramore Construction to address access issues to foundation sites and ran 24 hour shifting to address the schedule constraints of the winter construction season. To withstand the harsh environmental conditions while meeting the unique foundation needs of each tower type, Almita employed separate helical pile arrangements. Under each lattice tower base is a group of helical piles tied together with a common steel cap. Under each monopole tower is a group of helical piles with grillage beam connections and adjustable frames for each tower type.
Working within a tight timeline Almita produced 3045 helical piles and 2100 extensions for the lead piles. Foundation types varied from 4 piles to 48 piles per structure. Pile types varied from 25 ft. pile leads with double helixes up to 70 ft. including pile leads and 2 extensions with up to 7 helixes in total. In addition to pile installation, Almita was also responsible for cap welding, grillage installation, survey, and pre-drill. The final cost of this project, accounting for design, fabrication, installation, and project management totalled $20.5 million.