Recently there has been road construction around on the main road leading into my office building. I observed the construction crew removing asphalt in the form of a trench as showed in pictures below. Later on they filled up with aggregate and poured a layer of black tar and filled with something. The trench has been filled and resurfaced in line with the existing road surface.
Attach is the before picture (Satellite) captured from google maps.
Attach is the before picture (Street) captured from google maps.
Question: The rain water is being directed to a near by manhole. What is the engineering explanation for digging the trench later on was poured with liquid tar (asphalt crack filler)?