Canadian Consulting Engineer

Bridge-Plate Structure on Road to Whistler

British Columbia Highway No. 99 is a critical transportation route between Vancouver and Whistler, the site of the 2010 Winter Olympics.As part of a larger project that involved UMA Engineering (preli...

January 1, 2004   Canadian Consulting Engineer

British Columbia Highway No. 99 is a critical transportation route between Vancouver and Whistler, the site of the 2010 Winter Olympics.

As part of a larger project that involved UMA Engineering (preliminary design) and SNC-Lavalin (project management) to improve and widen the highway, Earth Tech Canada did detail design for the 7.2 km section between Culliton bridge and Cheakumus Canyon. The section crosses Conroy Creek, a mountain stream that is home to a resident population of Rainbow Trout. The road was widened to three lanes and had its alignment straightened.

Armtec provided pre-design technical support to Earth Tech, offering a new Bridge-Plate cross-section shape. To improve the fish passage, the structure has a flat gradient, with an open bottom arch with a span of 10.2 m and rise of 4.8 m.

As part of the tender process, Armtec prepared a set of preliminary installation and assembly drawings for a 30-m long bridge-plate structure along with cast-in-place concrete footings and gravity end walls. After the $18.2 million dollar construction contract was given to Bel Contracting, Armtec and Bel lengthened the structure to 33.7 m. The upstream end wall was eliminated in favour of a rip-rap/non-woven geotextile (Armtec 350) slope and cast-in-place end collar. The downstream end was redesigned with a cast-in-place end collar in conjunction with Lock-Block Wingwalls, reinforced with Armtec Mirafi 8XT polyester geogrid.

The bridge-plate structure was assembled, tightened and backfilled in under 10 working days, making it possible to finish the project by the fish window deadline. To armour the footings inside the structure without boulders, Bel installed 25 kg. size rip-rap directly above the footings and pumped concrete into the voids. A 300-mm thick layer of fish gravel was placed above the rip-rap. Armtec retained McElhanney Consulting to do detailed design and field certification.

After a few weeks the structure was subjected to a historic flood in October 2003 and ran near its hydraulic capacity. The design proved successful.

Article supplied by Armtec Limited of Richmond, B.C.

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