You bid a foot and the mill sells you a ton
You priced a hundred dollars a foot of casing, then the mill quoted by the ton at a wall thickness the engineer moved during review.
A framer buys lumber by the board foot and bids by the board foot, so the two units move together. Here the revenue unit and the purchase unit measure different things, and the conversion between them is controlled by a design engineer who can change wall thickness after your number is already in. The longest crossings carry the most tons, so your best looking bid item is also your largest unpriced position.
The size of it
A wall change or a mill move between bid and buyout falls entirely on you, and a hard bid unit price contract gives you no mechanism to push it back.
Casing, liner plate, and jacking pipe are steel, priced off mill pricing at buyout and sold by the ton. Your bid item is a linear foot of installed bore. Wall thickness comes out of jacking force and cover requirements, so a spec revision from 0.375 to 0.500 wall adds tonnage without adding one billable foot. On public utility and DOT unit price work, steel escalation language is routinely struck out; fuel escalation sometimes survives, and steel escalation almost never does.
Three moves, in order
Step 04: Estimating system
The estimate maps one to one onto the job cost codes, so variance means something the day it appears.
What else costs tunnel contractors money
The same mechanism in other trades
What tunnel owners ask
Casing wall thickness increase after bid on unit price bore?
You priced a hundred dollars a foot of casing, then the mill quoted by the ton at a wall thickness the engineer moved during review.
What does it cost?
A wall change or a mill move between bid and buyout falls entirely on you, and a hard bid unit price contract gives you no mechanism to push it back.
What do I do first?
Carry casing on the bid sheet in pounds per foot at the specified wall, with tonnage, the mill quote, and the quote date attached, so you can prove what you priced.
What are tunnel contractors supposed to be making?
Tunnel runs 23% gross margin, 16% overhead and 7% net profit before taxes at $1M–$5M. The all-trade average is 7%, so this trade sits right on it. The CFOS target is 10%.
Which part of the system fixes it?
The step is number 04, estimating system. The estimate maps one to one onto the job cost codes, so variance means something the day it appears. It comes from chapter 4 of CONTROL: The Construction Financial Operating System.
Josh Luebker ran commercial construction projects before he ran the numbers behind them, on data centres, military bases, hospitals, and high-rises. He wrote CONTROL: The Construction Financial Operating System, which is an eight-step framework for commercial subcontractors, and it publishes on October 1, 2026. He is a master electrician who moved into the office and kept the field vocabulary.
Sulphur Prairie Operations LLC maintains the benchmark reference behind these figures. Every edition is reconciled against the newest CFMA survey release before it publishes here. Where a figure changes between editions, the older edition keeps its year in the title so a citation to it stays correct.