Excavation
Unit-Price vs. Fixed-Bid Excavation: When Each Wins (Oregon)
Cojo
June 19, 2026
6 min read
A unit price excavation contract pays by the measured quantity, such as per cubic yard of dirt moved, per linear foot of trench, or per ton hauled, instead of one fixed total. It wins when the real quantity cannot be known until you dig, which in Oregon usually means rock excavation or over-excavating unsuitable soil. A fixed bid wins when the scope is clear and measurable up front, because it caps your price and shifts the quantity risk to the contractor. The key to a fair unit-price contract is that quantities are measured and verified, not guessed, so it never becomes a blank check. Most jobs use a mix: a fixed bid for the known work and unit prices for the uncertain parts.
In a unit-price contract, you and the contractor agree on a price per unit before work starts, then pay for the units actually used. Common excavation units are cost per cubic yard of soil or rock moved, price per linear foot of trench, and price per ton of material hauled off. The contractor cannot inflate the rate later, and you only pay for what is genuinely done. For where this fits in hiring decisions, see our excavation cost and hiring guide and the trade overview in our Oregon excavation contractor guide.
| Situation | Better Fit | Why |
|---|---|---|
| Scope and quantities are clear | Fixed bid | Caps your price, contractor owns the risk |
| Quantity unknown until you dig | Unit price | You pay only for what is actually moved |
| Possible hidden rock | Unit price line | Rock volume cannot be known up front |
| Over-excavating soft soil | Unit price line | Bad soil depth varies across the site |
| Simple, visible dirt work | Fixed bid | Easy to measure, no surprises |
| Mixed certainty | Both | Fixed for known work, unit for unknowns |
A unit-price contract is only fair if the quantities are documented. Good practice includes:
Without measurement, "per yard" is just a slogan. With it, you can check the math. This verification is also where a unit-price contract differs from a vague hourly arrangement; for that comparison, see hourly vs lump-sum excavation pricing.
The contract type changes the whole experience of the project, not just the final bill. Under a fixed bid, the price is set, so once you sign you mostly stop thinking about cost and the contractor carries the risk of surprises; if the dig is harder than expected, that is the contractor's problem, not yours. The flip side is that a contractor pricing a fixed bid on uncertain ground has to pad for the worst case, so you may pay for risk that never materializes. Under a unit-price contract, you stay engaged: quantities are measured as the work proceeds, you see the running tally, and you only pay for what is actually done, but you also carry the quantity risk and have to trust the measurement.
Neither feel is better in the abstract; they fit different temperaments and different jobs. A homeowner who wants a number and never wants to think about it again is happier with a fixed bid on well-defined work. A homeowner who would rather pay for exactly what was needed, and is willing to watch the truck tickets, does well with unit pricing on uncertain work. The mistake is mismatching them: a fixed bid on truly unknown rock either gouges you or burns the contractor, while a unit price on simple visible dirt work just adds measurement overhead to a job that did not need it.
Two situations push Oregon excavation toward unit pricing again and again:
You cannot see how much basalt or fractured rock is under a Central Oregon lot until the bucket finds it. A contractor who fixed-bids unknown rock either pads the price heavily to protect themselves or gets burned. A unit price per cubic yard of rock removed is the fair way to handle it: you pay for the rock that is actually there.
When a building pad sits on soft, wet, or organic soil, the fix is to dig it out and replace it with engineered fill. How deep the bad soil goes varies across the site, so a unit price per cubic yard of over-excavation and import fill keeps it honest.
The fear with unit pricing is an open-ended bill. Protect yourself with a few terms:
Industry Baseline Range: Sample unit-price line items often run $8 - $40+ per linear foot for trenching, dump truck haul-off at $250 - $750+ per load, fill dirt delivered at $20 - $75+ per cubic yard, and rock work carrying a premium per cubic yard well above ordinary dirt.
These are industry baseline ranges for planning only -- actual pricing depends on site conditions, soil, access, depth, haul-off, and current market conditions. Get a site-specific quote.
Real costs often run 2-3x baseline when rock turns out deeper than expected, when unsuitable soil runs across the whole pad, or when permits and disposal fees stack on top. That variability is exactly why these items go to unit price in the first place.
Use a fixed bid for the work you can see and a unit price for the work you cannot, and insist that unit quantities are measured and verified. That structure gives you a capped price where it is possible and fairness where it is not. To understand how the document itself reads, see bid vs estimate difference. Cojo is CCB Licensed and Insured across Oregon. See our excavation services and request a free estimate.
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