Subsurface surprises are a classic federal construction risk: unknown utilities, groundwater, rock, unsuitable soil, concealed structures, or conditions materially different from what the contract indicated. The federal clause creates an adjustment mechanism, but it also puts heavy emphasis on prompt written notice before the condition is disturbed.
A subcontractor must then determine whether its own agreement preserves a comparable path through the prime.
The FAR recognizes two categories
FAR 52.236-2 addresses subsurface or latent physical conditions that differ materially from those indicated in the contract, and unknown unusual physical conditions that differ materially from those ordinarily encountered in work of the character provided. The clause requires prompt written notice before the conditions are disturbed.
Official source: FAR 52.236-2 — Differing Site Conditions.
The subcontract can create a notice mismatch
A prime may have one deadline to notify the Government while requiring its subcontractor to notify the prime much sooner. That shorter downstream period can be commercially understandable, but it must be operationally realistic. Field personnel need to know the subcontract deadline, not just the FAR clause.
- Photograph and map the condition before disturbing it.
- Identify the contract drawing, boring, specification, or other indication that differs.
- Record labor, equipment, quantity, and schedule effects separately.
- Send notice to the exact contractual recipient.
- Avoid characterizing changed work as included scope before entitlement is evaluated.
Do not let the evidence disappear
The requirement to notify before disturbance is practical as well as contractual: once excavation continues, the prime and Government may lose the opportunity to investigate the original condition. When safety or protection requires immediate action, document why and preserve as much evidence as possible.
Check sponsorship and recovery terms
Because the subcontractor generally cannot submit a Contract Disputes Act claim directly against the Government, differing-condition language should be reviewed alongside pass-through claim, notice, change, and continue-performance provisions.