Originally Posted by Calgarian
I don't get why they can't do it all in one go. Why spend 3 years ripping it all up and re-paving the whole road to come back again the next year and rip it all up again, seems horribly inefficient.
Because if they did it all right away, they would most likely have to redo it in a few years anyway. If you completely shut down a road, rebuilt it all at once, then you might be able to avoid it - other than putting a finish coat of asphalt on a few years later. However, when they have to keep roads open, that means that they have to do work in little pieces, which means that different sections will be compacted to slightly different levels, and will settle differently. The only solution then is to redo it all once all of the other stuff is complete (and then still put on the final layer of asphalt a couple of years later).
The roadway on top of the new LRT tunnel under 64th Ave for the new LRT extension has now been redone 4 times, at least. The ground just keeps settling. Immediately on top of the tunnel, the depth of backfill is quite little, but the depth of backfill just beside the tunnel is the depth of the whole tunnel. I know they have filled the holes a couple of times, and also have taken everything out down to a metre or two below the top and then redone it a couple of times too. The final asphalt layer won't go on until it stops settling.
Either way, it's the contractors spending the money. If it were cheaper to do it all at once, I'm sure they would do it that way.