The Geotech Set Your Price and Never Signed It
You priced pumps, fuel, and rental days against a gallons-per-minute number pulled from borings somebody else paid for, and the subsurface came in wetter.
Other trades price quantities they can measure on a drawing. You price a subsurface behavior somebody else modeled, and the variance between the model and the site conditions falls entirely into fuel and rental, the two lines almost nobody reviews weekly. By the time the overrun is visible in the monthly financials, the pumps have already run the extra days.
The size of it
Flow materially above the modeled rate turns a profitable lump sum into a loss with no contractual recovery, and it registers as fuel and rental days rather than as a change order anyone will read.
No published benchmark reference breaks this trade out on its own. CFMA reports at NAICS level, and at that level this trade rolls into a broader bucket with several others. That's why this page carries mechanisms and no margin figures. It reports inside NAICS 238910 Site Preparation, so there's no dewatering margin figure to put in this box. The 48 trades that do publish average 7% net profit at $1M–$5M before taxes, which is the nearest reference point worth anything here.
Your commodity exposure here is diesel and pumping duration. The lump sum was built against an assumed gallons per minute and an assumed run length, both taken from a geotech report you didn't commission and can't cross-examine. If flow comes in above the model and the drawdown target doesn't change, you add pumps and burn fuel and rental days for no more money. HDPE header and discharge pipe is resin-priced, so that moves on you too. Specs commonly say nothing about who carries a groundwater condition worse than assumed, and escalation or flow-rate qualification language rarely survives a subcontract review.
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 dewatering contractors money
The same mechanism in other trades
What dewatering owners ask
Who pays when dewatering flow is higher than the geotech report assumed?
You priced pumps, fuel, and rental days against a gallons-per-minute number pulled from borings somebody else paid for, and the subsurface came in wetter.
What does it cost?
Flow materially above the modeled rate turns a profitable lump sum into a loss with no contractual recovery, and it registers as fuel and rental days rather than as a change order anyone will read.
What do I do first?
Write the assumption into the proposal in plain numbers: gallons per minute, pump count, and run length, citing the boring log and report date you priced from. That single sentence is what converts a wetter hole into a conversation.
Are there published benchmarks for dewatering?
No, and this site won't print one. No published benchmark reference breaks this trade out on its own. CFMA reports at NAICS level, and at that level this trade rolls into a broader bucket with several others. That's why this page carries mechanisms and no margin figures. In the surveys it rolls into NAICS 238910 Site Preparation, so the closest honest reference is the 48-trade table, where net profit at $1M–$5M averages 7% before taxes. Read that as the neighbourhood, and read your own job costing as the answer.
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.