Growth in the city of Edmonton, Alberta, demanded an alternate access route around the city. The Northwest Anthony Henday Drive Project was designed to provide a faster and more efficient route into and out of the city. Tetra Tech was part of the design-build contractor’s engineering team for this $1.2 billion project financed jointly by the Province and the concessionaire Bilfinger BOT Berger.

The Northwest Anthony Henday Project consists of approximately 25 kilometers of new divided, limited-access highway, including eight new interchanges and 29 new bridge structures. Tetra Tech provided geotechnical, materials, and pavement engineering as part of the design-build contractor’s engineering team. These services included preliminary design, detailed design, and engineering services during construction.

The key technical design challenges of this project were evaluation of high approach fills above weak and consolidating soils, optimization of deep pile foundations, mechanically stabilized earth wall design, and frost heave mitigation. Tetra Tech monitored the high fills during placement to maintain adequate stability and to determine when sufficient consolidation had occurred to allow deep foundations to be installed. For pavements, Tetra Tech evaluated the strength and condition of the existing pavement structure of cross roads and previously constructed mainline segments to provide pavement rehabilitation and reconstruction options.

Tetra Tech recommended the installation of wick drains to speed up consolidation times at locations where high approach fills were constructed. The use of lightweight foam was incorporated into approach fills to aid in achieving stability during construction and to help minimize girder lengths and the number of spans required. Tetra Tech performed pile load testing to optimize the design of cast-in-place and driven steel piles for bridge foundations, which resulted in substantial construction savings. To optimize pile design, Tetra Tech used pile driving analyzer testing extensively for driven steel H-piles and pipe piles.