The Underground Gamble: How to Estimate Civil Risks Without Losing Your Shirt
In heavy civil construction, the "dirt" numbers are usually straightforward. We know how much a scraper moves in an hour. We know the price of asphalt per ton. But underground utilities? That is the Wild West of estimating.
The underground scope is where companies go to die. It is where the biggest variables live: water, rock, unknown obstructions, and soil stability. If you bid underground work based solely on linear footage and an optimistic production schedule, you aren’t estimating—you’re gambling.
Here is how we approach the art of estimating the unseen, ensuring that when we win a bid, it’s a job we actually want to build.
1. Interrogating the Geotech Report
Amateur estimators look at the borehole summary and move on. We look at the logs like a detective examining a crime scene.
Water Table Fluctuations: If the bore log says water was found at 8 feet, and our trench is 10 feet, we don't just budget for a pump. We budget for rock bedding, slower production rates, and potential trench instability.
The "Refusal" Clause: We look closely at "blow counts." High blow counts mean hard digging. If the report mentions "auger refusal," we aren't sending a standard excavator bucket; we are pricing hammers, rock teeth, and lower cycle times.
2. The "Perfect Day" Fallacy
Software like HCSS or HeavyBid is great, but it’s dangerous in the hands of someone who has never been in a trench.
The Mistake: Estimating based on a perfect day where the trucks never stop, the pipe fits perfectly, and the inspector is in a good mood.
The Reality: We apply an Efficiency Factor. We know that a crew capable of 200 LF/day might only average 140 LF/day once you account for weather, safety meetings, moving shoring boxes, and waiting on density tests. We bid on reality, not best-case scenarios.
3. Logistics: The Hidden Cost of Dirt
Digging the hole is the easy part. Managing the spoil is where the money burns.
Haul-Off vs. Balance: Can we use the native soil as backfill? If the specs require imported engineered fill and we have to haul off the native clay, the cost of that trench just tripled (trucking out, tipping fees, material purchase, trucking in).
Staging Constraints: In tight urban corridors, you can't just pile dirt next to the trench. You might have to load it directly into trucks. This "load-and-go" operation slows down the excavator significantly. We price that downtime.
4. Reading the Fine Print: "Unclassified Excavation"
This is the scariest phrase in a contract.
The Trap: "Unclassified Excavation" means you own whatever you find down there—trash, boulders, old foundations—at the bid price.
Our Strategy: When we see this, we assess the risk profile. If the site has a history of industrial use, we qualify our bid or add a contingency. We are transparent with the client: "We can give you a lower price with a rock clause, or a higher price to cover the risk of 'unclassified.' Which do you prefer?"
5. Depth Brackets Matter
Installing pipe at 6 feet is a fundamentally different activity than installing it at 14 feet.
At 6 feet, you might slope the trench.
At 14 feet, you need a serious trench box or slide rail system.
The Estimating Rule: We break our bid items down by depth brackets (0-8', 8-12', 12'+). This ensures that if the design changes and the pipe goes deeper, we are paid for the exponential increase in effort, not just the linear footage.
The Bottom Line
A low bid might win the job, but a smart bid keeps the doors open. We pride ourselves on submitting numbers that are competitive but complete. We don't believe in hitting clients with surprise change orders for things we should have caught in the plan room.
When you hire us, you’re hiring a team that has already built the job in our heads before we ever move a spoonful of dirt.
