(30 ILCS 557/10)
    Sec. 10. Contract requirements. If a contract between a contractor and a governmental entity for an improvement exceeds $75,000, all of the following provisions apply to that contract:
    (1) If a contractor discovers one or both of the following physical conditions at the surface or subsurface of the site, the contractor must notify the governmental entity of the condition, in writing, before disturbing the condition:
        (A) A subsurface or latent physical condition at the
site differing materially from conditions indicated in the contract.
        (B) An unknown physical condition at the site of an
unusual nature differing materially from the conditions ordinarily encountered and generally recognized as inhering in work of the kind provided for in the contract.
    (2) If the governmental entity receives notice from the contractor under subdivision (1), the governmental entity must promptly investigate the physical condition.
    (3) If the governmental entity determines that the physical condition (i) does materially differ from the conditions indicated in the contract or ordinarily encountered in the work of the kind provided for in the contract and (ii) will cause an increase or decrease in the costs or time needed to perform the contract, the governmental entity must make an equitable adjustment to and modify the contract in writing.
    (4) The contractor may not make a claim for additional costs or time because of a physical condition at the site, unless the contractor has provided notice to the governmental entity under subdivision (1).
    (5) The contractor may not make a claim for an adjustment after the contractor has received a final payment under the contract.
(Source: P.A. 91-647, eff. 11-30-99.)