Differing Site Conditions: Who Pays for the Surprises Underground?

A differing site conditions (DSC) clause typically covers two categories. Type I conditions are subsurface or latent physical conditions that differ materially from what the contract documents indicated — the borings showed sand, but the excavation hits rock. Type II conditions are unknown physical conditions of an unusual nature that differ materially from those ordinarily encountered in the type of work — an undisclosed buried structure, an unexpected aquifer, contaminated soil.

When a DSC clause applies and the contractor gives proper notice, it may obtain an equitable adjustment of both the contract price and the time for performance to account for the unforeseen condition.

Without a DSC clause, the common-law rule in many jurisdictions places the risk of unforeseen subsurface conditions on the contractor, who is presumed to have accounted for site risk in the bid. That default forces contractors to either carry large contingencies — making their bids less competitive — or gamble that the ground is as expected.

A DSC clause reallocates that risk to the party best positioned to bear it, usually the owner, who controls the site and commissioned the geotechnical investigation. Far from being a giveaway to contractors, a DSC clause generally benefits owners by letting bidders price the work without padding for hidden-condition risk, producing lower, more competitive bids.

Owners frequently try to claw the risk back. They couple any geotechnical data with a disclaimer stating that the data is provided 'for information only,' that contractors may not rely on it, and that bidders are responsible for their own independent site investigation. These exculpatory and site-investigation clauses are designed to shift subsurface risk back to the contractor even where a DSC clause nominally exists.

Courts treat such disclaimers with varying deference. A broad disclaimer can defeat a Type I claim by negating reliance on the contract indications, but some courts refuse to enforce disclaimers that would render a DSC clause meaningless, especially where the owner had superior knowledge of the conditions. The interaction between the DSC clause and the disclaimer is where these disputes are won and lost.

DSC clauses almost always require prompt written notice upon encountering the condition and before it is disturbed, so the owner can investigate the condition for itself. A contractor that excavates through the surprise condition and then claims a DSC weeks later has often forfeited the claim, because the owner was denied the chance to verify what was actually there.

The discipline is to stop, document, and notify the moment a condition looks materially different from what was expected — photographs, surveys, and written notice — and to preserve the condition for inspection where feasible.

Before bidding, read the geotechnical reports and the disclaimer language together to understand how much subsurface risk the contract actually transfers. Confirm a DSC clause exists and that the notice procedure is workable. Where the owner has disclaimed all reliance on its own site data, treat that as a meaningful risk to price or to push back on — a DSC clause gutted by a broad disclaimer offers far less protection than it appears.