Bloom Lake Cofferdam and Trestles, Labrador



HEC was engaged by Dexter Construction to design a cofferdam to facilitate the construction of a large, cast in place concrete culvert structure near Bloom Lake, Labrador. The existing waterway was diverted with an earthen berm in order to develop the site, however the new construction, immediately adjacent to the berm, required excavation and concrete work well below water level and into the berm. Extremely difficult geotechnical conditions were encountered at the site making both the design and construction of the cofferdam and the construction of the new structure difficult. HEC developed the detailed design of the cofferdam as well as a full construction phasing procedure for the temporary works and the new structure that minimized the costs and installation schedule of the temporary works while allowing the new structure to be constructed in a timely and economical manner. HEC recommended changes to the parent design of the culvert structure that simplified the construction process while maintaining the intent of the original design. This project is a good example of HEC’s unique global thinking approach to a challenging project.


HEC designed two temporary construction trestles across local waterways near Bloom Lake, Labrador. The sites were called the Walsh Site Trestle and the Canning Site Trestle. The Canning Site Trestle was a 21.4 m, two span steel girder structure with a timber deck, supported on central pier that featured end bearing piles and on abutments constructed out of large timber mats.  One of the trestle abutment foundations was a timber mat found on site. Longitudinal restraint for the structure was achieved using driven pile dead man elements at one end of the structure that worked for longitudinal loads in two directions. The design and production of construction drawings for the Canning Site Trestle was fast-tracked and was completed in a single weekend, thereby maintaining a critical schedule milestone for our client. While we feel we always provide exceptional service for our clients, the Canning Site Trestle project is a prime example of HEC putting in the extra effort when required to meet a challenging deadline and our ability to use all available materials in an attempt to provide the highest value and practical designs to our clients. The Walsh Site Trestle was a 10.35 m single span, steel girder structure supported on timber mat foundations at each end. Both structures were designed for exceptional loads including large, loaded Volvo trucks transporting materials from a nearby site.

Client: Dexter Construction

Value: $400K Cofferdam, $200K Trestle

Year: 2009

Role: Detailed Design Engineer