Metro Line 4 Maintenance Depot

The challenge

Rail infrastructure does not forgive ordinary building tolerances. The track slab had to be level to within three millimetres over eighteen hundred metres, and the inspection pits had to align with equipment that was still being manufactured in another country.

Our approach

We surveyed with robotic total stations tied to permanent site monuments, and re-checked every pour against them rather than against the previous section. Errors that would normally accumulate along the length of a slab had nowhere to go.

For the equipment interfaces we built to the manufacturer's models rather than the tender drawings, and cast in adjustable baseplates with forty millimetres of tolerance in every axis. When the plant arrived eleven weeks late, none of it needed a single core drilled.

The outcome

The track slab was accepted on first survey with a maximum deviation of two millimetres. The depot went into service on the original operational date despite the equipment delay, and the consortium named us preferred contractor for the Line 6 stabling facility.