Uncertainty should be managed through a defined process. A contingency can help plan for discoveries, but the contract should still explain documentation and approval for additional work. An unexplained reserve does not replace an accountable change process.
What to do next
Ask who can authorize changes and how urgent discoveries will be communicated. Keep photographs and revised scope records together. Review unused allowances and final quantities at closeout according to the agreement rather than assuming every planned amount was necessarily spent.
Related Perkins guidance
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