48 CFR § 52.243-5 - Changes and Changed Conditions.
As prescribed in 43.205(e), insert the following clause:
(a) The Contracting Officer may, in writing, order changes in the drawings and specifications within the general scope of the contract.
(b) The Contractor shall promptly notify the Contracting Officer, in writing, of subsurface or latent physical conditions differing materially from those indicated in this contract or unknown unusual physical conditions at the site before proceeding with the work.
(c) If changes under paragraph (a) or conditions under paragraph (b) increase or decrease the cost of, or time required for performing the work, the Contracting Officer shall make an equitable adjustment (see paragraph (d)) upon submittal of a proposal for adjustment (hereafter referred to as proposal) by the Contractor before final payment under the contract.
(d) The Contracting Officer shall not make an equitable adjustment under paragraph (b) unless -
(1) The Contractor has submitted and the Contracting Officer has received the required written notice; or
(2) The Contracting Officer waives the requirement for the written notice.
(e) Failure to agree to any adjustment shall be a dispute under the Disputes clause.