A $ 260 million modernization project along Highway 91C near Highway 17 in Delta, British Columbia, is far from a typical road reconstruction.
The artery sits between two very sensitive environmental features – the Fraser River and the Burns Bog – and as a result soil conditions are far from ideal, which has prompted the builder to use various techniques to modernize a existing interchange and allow construction. three new ones.
“The construction techniques used reflect these conditions, which are typical of construction in the Fraser River Delta region. Transport and infrastructure.
“Another challenge is construction in an active road and industrial area. Due to the complexity of the transportation system in and around the project site, effective traffic management is key to our success: minimizing disruption and maintaining traffic.
The project is designed to improve the operation of existing roads and make the roads safer and more efficient for local residents and commercial drivers. It includes upgrades to the existing interchange at Highway 91 and Nordel and the construction of three new interchanges – at Highway 91C and Nordel Highway, Highway 91C and Highway 17, and Highway 17 and River Road.
Work on the project began in spring 2020 and substantial completion is slated for fall 2022, with full completion in spring 2023. Pacific Gateway Constructors General Partnership, a consortium of Ledcor, Aecon and BEL Contracting, has won the design-build contract for the work in 2019.
The contractor uses three specific techniques to consolidate, stabilize and strengthen the soil to ensure that the soil can support the weight of the heavy exchangers. The techniques used are preloading and overloading, the installation of stone columns and the placement of pile foundations.
Preloading and overloading involves placing infill material, such as sand, on the soil surface before construction to consolidate and compress the underlying soil. Up to 600,000 cubic meters, or 240 Olympic swimming pools, a value of sand will be used for the pre-loading and backfill work.
With the installation of stone columns, a vibrating probe is used to push layers or columns of gravel into the ground. The vibrating action compacts the soil and creates a good base. Approximately 2,000 stone columns of varying depths will be installed in the project area, mainly in areas where road connections to new road bridges are being constructed.
Pile foundations will be used when the soil cannot support the weight of the structure being built without the possibility of the soil expanding, contracting or shifting. Thirty-two reinforced concrete piles will be used in the construction of the project’s bridges and viaducts, and 30 steel piles will be required for the overhead directional signage of the highway.
“Typically, a building contractor will choose which technique to use based on a number of factors, including soil conditions, loads, accessibility of the area, and available equipment,” Deane explains.
Embankment placement, embankment construction and stone column installation are currently underway on the project and foundation works, drilling of wells for the construction of bridges and viaducts has also started.
The area is a hive of activity with excavators, earthmovers and compactors, cranes, sweepers and hydrovac trucks on site.
Deane says that due to the complexity of the transportation system in and around the project site, effective traffic management is essential to minimize disruption and keep vehicles moving.
“Coordination is essential, both from the point of view of the construction phase and traffic management,” she says.
To ensure traffic flow, most layouts such as new roads, ramps and bridges are built outside of the existing roadway. Once they are built, traffic is diverted onto the new alignments, allowing the builder to modify the existing pavement for the new design. Once the existing highway pavement has been modified, the new configuration is open to traffic. Then the temporary roads and ramps are removed.
Because all roads are important and busy transportation routes, Deane says proactive planning and coordination with key stakeholders and other projects in the region is important to minimize disruption.
Another important consideration in improving the highway is maintaining the integrity of the nearby Burns Bog.
Deane says Pacific Gateway follows best practice construction management plans to avoid or minimize potential environmental impacts to Burns Bog, including air quality and dust control, soil erosion and sediment control, as well as the protection of vegetation, wildlife and aquatic resources.
The designer-builder has also obtained all necessary environmental permits for work in the area, which include obligations to protect and maintain adjacent environmental features, she said.
For example, drainage ditches on the project were designed to drain stormwater away from the bog. Artificial berms will also be constructed and planted next to the bog to reduce the intrusion of water other than the bog.
The province also conducts environmental monitoring during construction to ensure all requirements and commitments are met. Post-construction monitoring will be undertaken to confirm the effectiveness of long-term environmental protection measures.