Sitework: The One Bid Number That’s Always a Guess

The test pits came back clean. Soil and glacial till, no rock. The civil engineer signed off, the GC priced excavation as a standard dig, and the sitework number went into the bid alongside everything else, looking just as solid as the framing line and the roofing line.

Then the excavator hit bedrock at four feet.

Not a boulder. Bedrock, across most of the foundation footprint, in a place where the test pits had said soil. The hammer attachment came in. The schedule slipped. The sitework number that had felt like a fact at signing turned out to be a guess that everyone had agreed to call a price.

Of every line on a custom home bid, the one for sitework is the one most likely to be wrong. It’s worth understanding why before you sign any contract.

Why Sitework Is Different

Every other trade prices things that can be seen. Framing prices the lumber on a drawing. Roofing prices the square footage of a roof plane. Tile prices the area of the bathroom floor. Even mechanical prices a defined system in a defined space.

Sitework prices what’s under the ground.

Until the first cut goes in, every assumption underneath the bid is an inference. What the soils look like. How deep the rock line sits. Where the water table is. What the existing utilities actually do. The bid translates those inferences into a fixed number, and the number feels real. The conditions it’s pricing are not yet known.

This is true on raw land. It’s even truer on a renovation, where the unknowns include every pipe, line, and stub a previous owner installed without telling anyone.

Two Ways It Goes Sideways

The bedrock story is the canonical version. Test pits at the easy corners of the proposed footprint showed eight feet of clean soil. Standard dig. Mid-excavation, the center of the building hit rock that the test pits had simply missed because they were spaced wrong. Hydraulic hammering came in, two weeks fell off the schedule, and a five-figure overrun got added to a line item everyone had treated as settled.

The renovation version is uglier because it’s avoidable. On a Hudson Valley reno, the excavator unearthed an existing water service during foundation work and backfilled over it without flagging the location. The electrical and the sewer got marked and protected. The water line did not. Now we’re redigging to find it again, because we still need to know where it runs to plan around it. None of it would have happened if a single document had shown the line in the first place.

Both stories share the same root cause. The bid was generated before anyone had spent the time and money to actually know what was in the ground.

What to Require Before You Accept a Sitework Number

The fix is to require the inputs that make a real sitework number possible. Without them, what’s on the bid is a placeholder.

• A real geotechnical investigation. Not two test pits at the easy corners. A geotech report from a licensed engineer, with borings spaced and sampled to capture conditions across the actual building footprint. On a tricky site, this is a five-figure investment that pays for itself the first time it catches rock.
• A current survey with private utility locates. For renovations and infill sites, this is non-negotiable. A public 811 markout will identify active municipal services and stop there. A private utility locator finds the abandoned lines, the unmarked services, and the things the public locator misses by design.
• A full civil engineering set. A site plan tells you where the house goes. A civil set tells you the grading, the cut and fill volumes, the stormwater management, the driveway profile, and the sequence of how dirt actually moves on the site. Without it, your sitework bid is pricing assumptions about all of the above.
• Pre-negotiated unit prices for the unknowns. Even with the diligence, surprises happen. The contract should carry agreed unit prices for rock removal, unsuitable soils export, and dewatering, so that when something does come up, you’re not negotiating with a backhoe sitting idle on the clock.

The Takeaway

A sitework bid built on assumptions is a number everyone has agreed to pretend is a price until the dig proves otherwise. The cost of doing the real diligence — geotech and survey and civil and private utility location — is meaningful. It’s also a fraction of what a single bedrock surprise or severed water line will cost you mid-build.

If you’re about to sign a contract and the only sitework documentation is a site plan and a couple of test pits, don’t ask the GC for a sharper pencil. Pay for the diligence that turns the guess into a price.