Constructon Projects that last a while alost always have all of the paving done twice, and especially on projects like 16th Ave. The first time, they pave so that traffic can get going again after they have done work, knowing that they might need to cut into the pavement again later. No sense doing the finished project when you don't know if it's going to be cut into later. When all of the other work is done, and you know there aren't to be any more cuts, that's when the final paving is done.
For example, the four interchanges on Deerfoot that have been built in the last 8-10 years (Douglasdale, Barlow, 130th, McKenzie Towne). Only after ALL four were complete did they bring in the paving crews to put the final layer of pavement on the whole length.
Another reason why they do it twice (especially after digging holes underneath) is that is allows the dirt underneath to settle before putting the final layer on. The contractor misses a spot compacting the soil/gravel underneath, and a heavy truck drives over the paved spot later, instantly ruined driving surface. Paving it temporarily first allows all those spots to be found before the final surface goes on.
As far as the old trolley lines go, that's how paving is often done, just pave over top of what was there before. In many cases, there's not really a reason to remove the old before they place the new. They just remove a bit by the concrete curb so that they can make the pavement level with the concrete curb when it's done. Roadways are sloped anyway, so that water runs off towards the side.
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