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British Columbia Ministry of Transportation and Infrastructure (BCMoTi) is improving the West Side Road in stages since 2014. For a certain section along the road an attenuator was favored instead of draped mesh.
Rockfall impact attenuators intercept the trajectory, reduce potential bounce height, and dampen the rockfall velocity, therefore, attenuate the total kinetic energy of rockfall.
A controlled guiding of the rock(s) to a designated collecting area limits costly clean-outs in difficult terrain. This type of easy to install, low maintenance, passive rockfall mitigation system is increasing in popularity worldwide.
Geobrugg North America, LLC offered a proprietary attenuator system that fulfilled the BCMoTi's requirements. Ecora Engineering and Resource Group Ltd. was retained to be the Engineer of Record (EoR) specifically for the attenuator installation. Ecora confirmed the system location, dimensioned the system anchors, assured quality control of the installation and also submitted the record drawings. Geobrugg supplied a qualified, experienced representative to advise the contractor on installation procedures. Little Rock Drilling and Blasting Ltd. were contracted to perform the installation work.
The attenuator was installed on a rock-cut approximately 20 m above the West Side Road. Above the attenuator system, 30 m to 60 m of natural rock bluff represent a significant source of rockfall. By installing the attenuator close to the road, several advantages are highlighted: a large amount of mesh is saved when not draping the whole slope but allowing for some rockfall to be intercepted by the attenuator and then guided to the ground; furthermore, the attenuator could be located within the BCMoTi right-of-way, eliminating the need to access and construct on private land; finally maintenance is kept at a minimum thanks to the road's proximity.
It is easy to install with one single mesh type. No need to mix or layer meshes which takes time, waists material and increases exposure to workers. The mesh is simply attached to support rope with a Helix Coil or seaming rope.