When the K'atlodeeche Access Road was chip-sealed last fall, facetious users began to take bets on how long the surface treatment would last. "It will have potholes in a week" some predicted. "It's a quality government job, it will last forever" others retorted.
In the end, we were all wrong. The chip-seal lasted until after break-up, but when it broke down, it did so spectacularly. The surface crumbled and the sub-base turned out to be nothing but soft sand. Crews ripped off the rubble, installed a culvert, and chipped-sealed over again. No sooner were they gone than the road began to subside again. This time the failing section was simply topped with a big dump of asphalt. And the asphalt started sinking too. Guffaws all around.
Yet according to Earl Blacklock, spokesman for the Department of Transportation, the failure rate was not significant. "Only 60 lane-metres of the 17,200 lane-metres of work completed is in need of repair, for a 0.35% problem rate. Because of the low failure rate, we're confident that the design and construction work was solid" he told your correspondant in an email interview. The expected problem rate on this type of project is 2%.
There are no plans to install a culvert under the section that is continuing to fail, as the deterioration does not appear to be caused by drainage issues. A more likely cause is discontinuous permafrost, where freeze/thaw cycles can cause the sub-base to slump, particularly in combination with heavy loads. The behaviour of permafrost cannot always be predicted, and in this case could be related to the abnormally warm, snowy winter, and abnormally hot, dry summer.
Blacklock adds that the cost of asphaltic surface treatment is $50,000 per kilometer and the surface is expected to last seven years under normal circumstances. So, despite the spectacularly boondogglish appearances and the scepticism of locals, the GNWT has the situation under control.
In the end, we were all wrong. The chip-seal lasted until after break-up, but when it broke down, it did so spectacularly. The surface crumbled and the sub-base turned out to be nothing but soft sand. Crews ripped off the rubble, installed a culvert, and chipped-sealed over again. No sooner were they gone than the road began to subside again. This time the failing section was simply topped with a big dump of asphalt. And the asphalt started sinking too. Guffaws all around.
Yet according to Earl Blacklock, spokesman for the Department of Transportation, the failure rate was not significant. "Only 60 lane-metres of the 17,200 lane-metres of work completed is in need of repair, for a 0.35% problem rate. Because of the low failure rate, we're confident that the design and construction work was solid" he told your correspondant in an email interview. The expected problem rate on this type of project is 2%.
There are no plans to install a culvert under the section that is continuing to fail, as the deterioration does not appear to be caused by drainage issues. A more likely cause is discontinuous permafrost, where freeze/thaw cycles can cause the sub-base to slump, particularly in combination with heavy loads. The behaviour of permafrost cannot always be predicted, and in this case could be related to the abnormally warm, snowy winter, and abnormally hot, dry summer.
Blacklock adds that the cost of asphaltic surface treatment is $50,000 per kilometer and the surface is expected to last seven years under normal circumstances. So, despite the spectacularly boondogglish appearances and the scepticism of locals, the GNWT has the situation under control.
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