The method statement for digging the basement, C01, is briefed to the gang and pinned to the cabin wall. Everyone signs the briefing sheet.
Briefing and permits
The back alley's bill so far: 98 weeks · See the bill
The gang builds from what they're told. Tell them from the current me, and check the sums behind the lift.
The wrong way
The ground is wetter than expected. The shoring changes, and the method statement goes out again as C02, by email, to someone on leave.
Assistant engineer Rex's crane pad calculation gets a tick in the corridor. Nobody looks at the escalator weight going in. It came from C01. The escalators are heavier now.
A new gang starts. The supervisor briefs from the copy on the wall: C01. They dig the old way.
One side of the dig slumps. Nobody is in it. It's close.
The crane arrives, hired by the day. Gary, the lift supervisor, reads the escalator weight off the delivery note. The crane goes home without lifting anything.
Gary: That's not what your calc says.
The wall said C01, the inbox said C02, and the crane went home without lifting anything.
+3 weeks on the back alley's bill: A briefing on the old version and a calculation nobody really checked: a slumped dig, a stopped lift and a redesigned crane pad.