Virginia Falls is located along the South Nahanni River in the remote and pristine Nahanni National Park Reserve in the Northwest Territories. Nahanni National Park is a popular tourist destination accessible only by river or air. A float plane docking facility is located approximately 800 metres upstream of Virginia Falls and connects to a boardwalk system that provides access to a campground and a hiking trail. The floating dock and ramps are seasonally removed before freeze-up in the fall and re-installed in the spring after ice break-up.
Over the years, the ramp and boardwalk experienced foundation stability issues, as well as damage from seasonal installation and beaching activities, requiring annual maintenance and repair to the floating dock system. The costs of maintenance and short-term fixes were significant for Parks Canada, considering the required frequency for repairs and the remoteness of the site. Parks Canada needed a long-term replacement solution to these issues to continue facilitating access to Virginia Falls and the campground.
Parks Canada retained RTL Construction with Associated Engineering for a design-build project to replace the float plane dock facility, with Associated providing structural engineering and construction inspection services for the float plane dock replacements.
This fast-track project was awarded in July 2018, with detailed design performed within weeks. Shop fabrication was completed in August, and the dock was installed in September 2018. We worked closely with RTL and its subcontractors to meet the quick turnaround of deliverables during the three-week detailed design period.
As part of a fast-track design-build, Associated Engineering helped develop a replacement dock system including three light-weight removable docks and ramps connected to partially buried anchor foundations. The facility includes floating dock modules with galvanized steel frames, lightweight aluminum gangway ramps, galvanized steel grillage foundations, and float chain anchorages. All dock and ramp units were designed to weigh less than 450 kilograms to allow for seasonal removal by helicopter.
Project Manager, Karine Poliquin, tells us, “Due to the remoteness of the site, during construction, all equipment and construction material were flown in by helicopter from Nahanni Butte, approximately 90 minute round trip. This posed limitations on the type and size of equipment and construction materials brought to site.” The largest piece of equipment flown in was a mini excavator weighing 1,000 kilograms.
Parts of the steel grillage frame were transported in small bundles, and then assembled on-site. During design, the team revised the original bid concept, from a welded grillage to a bolted assembly, to make transportation to site by helicopter feasible, and for ease of assembly with minimal equipment.
A further challenge arose when the site reconnaissance survey revealed insufficient suitable backfill material at one foundation in a low-lying area near the river. This foundation grillage required a redesign just weeks before mobilization, and suitable granular material was flown in by helicopter from a location seven kilometres away.
“Despite the unseasonably cold conditions, construction was successfully completed ahead of schedule. Our design helped to optimize the helicopter transportation, which was a crucial, weather-dependent aspect of construction.”