Differing Site Conditions Clause: Notice, Claims, and Recovery

The differing site conditions clause, found at FAR 52.236-2, shifts the risk of hidden or misrepresented subsurface conditions on federal construction contracts from the contractor to the government. When the ground doesn’t match what the contract documents described, or when a contractor hits something so unusual that no reasonable bidder would have anticipated it, the clause allows recovery of added cost and time through an equitable adjustment. Getting that recovery depends on giving prompt written notice, preserving the evidence, and following the Contract Disputes Act procedures to the letter.

FAR 36.502 requires the contracting officer to include the clause in every fixed-price construction contract expected to exceed the simplified acquisition threshold. Below that threshold, inclusion is discretionary.¹ One boundary worth flagging up front: the right to relief for differing site conditions is not implied into a contract. On private work without a differing site conditions clause, the risk of unexpected subsurface problems falls entirely on the contractor, and broad disclaimers about site data become far more enforceable.

The Two Categories of Qualifying Conditions

The clause covers two distinct scenarios, and a claim has to fit one of them.

Type I: Conditions That Contradict the Contract

FAR 52.236-2(a)(1) covers situations where the actual ground conditions differ materially from what the contract documents indicated. The plans, specifications, or boring logs told the contractor to expect one thing, and the contractor found something meaningfully different. A boring log showing dry sand at foundation depth that turns out to be saturated clay is the classic example.²

A successful Type I claim requires three things. First, the contract must contain an affirmative representation about site conditions, whether that’s a geotechnical report, soil boring data, or specific callouts in the drawings. Second, the contractor’s interpretation of that representation must have been reasonable. Third, the contractor must have actually relied on that interpretation when pricing the bid. The difference between what was represented and what was found must be substantial enough to change the cost or duration of the work.

Type II: Unknown and Unusual Conditions

FAR 52.236-2(a)(2) addresses a different problem: conditions the contract never mentioned at all, but that no reasonable contractor would have expected. The contract doesn’t need to say anything specific about the subsurface. The question is whether what the contractor encountered departs materially from what’s ordinarily found on similar projects in similar locations.²

Discovering an abandoned underground storage tank where no records suggested one would be is a potential Type II condition. An old building foundation or unexpected hazardous material in an area with no history of prior development could also qualify. The test is objective: would a reasonably experienced contractor performing this kind of work in this location have anticipated this condition? Finding rock while excavating in a region known for rocky terrain almost certainly fails. The contractor carries the burden of proving the condition was both unknown at the time of contracting and unusual enough that standard pre-bid diligence wouldn’t have revealed it.

Pre-Bid Investigation Duties

The clause doesn’t let contractors bid blindly and then claim surprise. FAR 52.236-3 requires contractors to take reasonable steps to understand site conditions before bidding, including investigating transportation access, labor availability, weather patterns, ground conditions, and the character of equipment needed for the work. The contractor must satisfy itself about the “character, quality, and quantity of surface and subsurface materials or obstacles” to the extent that information is reasonably obtainable from a site visit, government exploratory work, and the contract drawings.³

A contractor who skips the site visit or ignores readily available information doesn’t get a free pass. The regulation is explicit: failing to investigate doesn’t relieve the contractor of responsibility for properly estimating the difficulty and cost of the work. The government also disclaims responsibility for any conclusions the contractor draws from the information provided, unless the contract expressly states otherwise.³

A related trap involves patent ambiguities in the contract documents. If a discrepancy is obvious on the face of the documents, the contractor has a duty to ask about it before bidding. A contractor who notices conflicting soil descriptions in the specifications and the boring logs but says nothing cannot later rely on whichever interpretation is more favorable. The ambiguity has to be raised during the bidding phase, or the right to rely on it may be lost.⁴

How Disclaimers on Site Data Are Treated

Owners frequently attach disclaimers to geotechnical reports and boring logs, warning that the data is for “informational purposes only” or is “not part of the contract documents.” These broad disclaimers rarely hold up. Courts have repeatedly found that an owner puts itself in a contradictory position when it provides site data to bidders but simultaneously disclaims liability if that data is wrong. When verifying the report independently would be unreasonable given bidding timelines and costs, contractors are generally entitled to rely on it despite the boilerplate language.

Narrow, specific disclaimers are another story. A disclaimer limited to a particular aspect of the report, such as exact utility locations or precise material quantities, is more likely to be enforced. The difference comes down to whether the disclaimer actually communicates a meaningful limitation or is trying to shift all subsurface risk back to the contractor while still expecting competitive bids based on the data provided.

Notice: Where Most Claims Fall Apart

FAR 52.236-2 requires the contractor to notify the contracting officer in writing “promptly, and before the conditions are disturbed.” The regulation does not specify a fixed number of calendar days. “Promptly” means as soon as the contractor recognizes something is wrong. “Before the conditions are disturbed” means the government has to have the opportunity to come look at the problem in place.⁵

The notice should describe the condition, identify its location on the site, and request that the contracting officer investigate and issue a determination. The contractor should also warn explicitly that performance will be delayed if instructions aren’t received within a reasonable period. If the contracting officer fails to respond or denies that a differing condition exists, the contractor should immediately put in writing that it disagrees and is reserving all rights under the contract.

Failing to provide written notice is not automatically fatal, but it creates a serious obstacle. If the government was already aware of the condition through its own inspector’s presence on site, that constructive notice may preserve the claim. The contractor must show that the lack of written notice didn’t prejudice the government’s ability to investigate or direct the response. That’s a much harder case to make than simply sending a letter. Written notice is always the safer path.

Watch for contract language making prompt written notice a “condition precedent to recovery.” That language is enforced literally in many jurisdictions, and missing a hard deadline can extinguish the claim regardless of how legitimate the underlying condition is.

Documenting the Condition

Before anything gets moved, covered, or remediated, the contractor needs to document the condition thoroughly. Photographs and video should capture the condition from multiple angles, with scale references and identifiable landmarks tying the images to a specific location and depth. Soil samples or fragments of unexpected material should be preserved and labeled with the exact coordinates and depth of discovery.

A comparison document is the backbone of the claim. This lines up the contract’s representations against the actual findings, referencing specific page numbers, drawing sheet numbers, and boring log identifiers. The goal is to make the mismatch unmistakable: the contract said X, reality is Y, and here is exactly where each representation appears in the documents.

The contractor also needs a preliminary cost impact analysis: additional labor hours, equipment rentals, material costs, and an estimate of the schedule delay. This doesn’t need to be final, but it frames the equitable adjustment negotiation and demonstrates that the condition has a real financial consequence.

Filing the Claim and the Decision Timeline

The claim is submitted to the contracting officer by whatever method the contract specifies, typically certified mail with return receipt or hand delivery, and increasingly through digital project portals. Proof of delivery matters because the date of receipt starts several important clocks.

Certification for Claims Over $100,000

Any claim exceeding $100,000 must include a certification signed by someone authorized to bind the contractor. The certification must state that the claim is made in good faith, that the supporting data are accurate and complete to the best of the contractor’s knowledge, that the amount requested accurately reflects the adjustment the contractor believes is owed, and that the signer is authorized to certify on the contractor’s behalf.⁶

A missing or defective certification doesn’t permanently destroy the claim, but it stalls everything. The contracting officer has no obligation to issue a final decision on an uncertified claim over $100,000 and can reject it within 60 days. A defective certification can be corrected before a court or board enters final judgment, but the delay and lost interest accrual make getting it right the first time worth the effort.⁶

Contracting Officer’s Decision

For claims of $100,000 or less, the contracting officer must issue a decision within 60 days if the contractor requests it in writing, or within a reasonable time otherwise. For certified claims over $100,000, the 60-day clock starts when the contracting officer receives the certified claim. If the decision won’t come within 60 days, the contracting officer must notify the contractor of the expected timeline within that same 60-day window. If the contracting officer fails to issue a decision within the required period, that failure is treated as a denial, and the contractor can appeal as though a written denial had been issued.⁷

Appeal Deadlines

A contractor whose claim is denied has two options, and the deadlines are rigid.

File a written notice of appeal with the agency Board of Contract Appeals within 90 days of receiving the contracting officer’s final decision, with a copy to the contracting officer who issued it.⁸
Or file suit directly in the U.S. Court of Federal Claims within 12 months of receiving the final decision.⁸

The Contract Disputes Act also encourages alternative dispute resolution. If a contracting officer rejects a request for ADR, the rejection must be in writing with specific reasons. A contractor who rejects the agency’s ADR offer faces the same requirement.⁹

What You Can Recover

The primary remedy is an equitable adjustment: a modification to the contract price and schedule that puts the contractor in the same position it would have been in had the conditions been correctly described. The contracting officer is required to investigate the site promptly after receiving notice, and if the conditions do materially differ, an equitable adjustment “shall” be made and the contract modified in writing.⁵

Direct costs include the additional labor, specialized equipment, and materials the contractor wouldn’t have needed if the contract had been accurate. Indirect costs are also recoverable: field overhead, extended general conditions, and the idle time of workers and equipment while the contractor waited for instructions. Home office overhead during a government-caused delay is calculated using the Eichleay formula, which is the exclusive method for that purpose on federal contracts. A reasonable profit margin on the additional work is typically included.

The remedy also includes a formal extension of the contract completion date, which protects the contractor from liquidated damages that would otherwise accrue during the delay. If an unexpected subsurface obstruction pushes foundation work back by two weeks, the overall project deadline should shift by the same period.

Under the Contract Disputes Act, the government pays interest on the amount found due from the date the contracting officer receives the certified claim, or from the date payment would otherwise have been due, whichever is later.¹⁰ For the first half of 2026, the applicable interest rate is 4.125 percent per year.¹¹

What You Cannot Recover

Two categories of costs that contractors routinely expect to recover are off the table on federal work.

Attorney fees and claim preparation costs are unallowable. FAR 31.205-47 specifically prohibits costs incurred in prosecuting claims against the federal government, including fees for lawyers, accountants, consultants, and the administrative expenses of preparing and presenting the claim. This catches many contractors by surprise, because the legal and expert costs of building a six-figure differing site conditions claim can be substantial.¹²

Anticipatory profits on work never performed are also not recoverable. The contractor can recover profit on additional work actually performed, but not the profit it expected to earn on original scope that was disrupted or delayed.

Keep Working While the Claim Is Pending

Discovering a differing site condition doesn’t authorize the contractor to stop work and wait for a check. The contractor must continue performing according to the contracting officer’s instructions while the claim is pending, even before any equitable adjustment has been agreed to. Refusing to proceed can turn a strong claim into a termination for default.

The mitigation obligation also means the contractor should take reasonable steps to minimize the impact. If there’s an obvious, cost-effective way to work around the condition while the claim is being resolved, sitting idle instead will undermine the recovery. The contracting officer should be given a chance to direct the approach, but if only one reasonable course of action exists, the contractor shouldn’t wait indefinitely for instructions that may not come.

Every communication should be in writing throughout this process. Verbal agreements and handshake understandings about how to handle the condition tend to evaporate when the change order negotiation gets difficult. A written record of each request, instruction, and objection protects the contractor’s position at every stage.

1
Acquisition.GOV. FAR 36.502 Differing Site Conditions
2
eCFR. 48 CFR 52.236-2 – Differing Site Conditions
3
eCFR. 48 CFR 52.236-3 – Site Investigation and Conditions Affecting the Work
4
United States Department of Justice. Civil Resource Manual – Ambiguities
5
Acquisition.GOV. FAR 52.236-2 Differing Site Conditions
6
Office of the Law Revision Counsel. 41 USC 7103 – Decision by Contracting Officer
7
eCFR. 48 CFR 33.211 – Contracting Officer’s Decision
8
Office of the Law Revision Counsel. 41 USC 7104 – Contractor Appeals
9
Administrative Conference of the United States. Contract Disputes Act Basics
10
Acquisition.GOV. FAR 33.208 Interest on Claims
11
Federal Register. Prompt Payment Interest Rate – Contract Disputes Act
12
eCFR. 48 CFR 31.205-47 – Costs Related to Legal and Other Proceedings