In infrastructure work the greater part of the construction becomes invisible once complete. That makes the timing of inspection critical: after a line has been closed, the only remaining check is to dig it up again when a problem appears.
The checks we make before closing: level and gradient measurement, suitability of the pipe bedding material, gasket inspection at the joints, pressure and leak testing and, where necessary, CCTV inspection of the line.
The backfill stage is part of the construction too. If the trench backfill is not compacted layer by layer, the route of the line will show up months later as a line of settlement in the road surface.
