(a) The department shall have the authority to contract as set forth in this article and in Code Section 32-2-2. All department construction contracts shall be in writing. Any contract entered into by the department for the construction of a public road shall include, as a cost of the project, provisions for sowing vegetation, if appropriate, on all banks, fills, cuts, ditches, and other places where soil erosion is likely to result from the necessary incidents to road work along the right of way of the road project.

(b) Persons, firms, or corporations submitting bids on department construction contracts are required to examine the site of the proposed work and determine for themselves the anticipated subsurface and latent physical conditions at the site prior to submitting a bid on the project. The submission of a bid shall be prima-facie evidence that the bidder has made such examination and is satisfied as to the conditions to be encountered in performing the work. The department does not in any way guarantee the amount or nature of subsurface materials which may be encountered and which must be excavated, graded, or driven through in performing the work on the project. The contractor shall not plead deception or misunderstanding because of variations from quantities of work to be performed or materials to be furnished as shown on the plans or minor variations from the locations or character of the work. Payment will be made only for actual quantities of work performed in accordance with the plans and specifications. The department shall not provide compensation above the amount bid on such project solely due to the encountering of subsurface or latent physical conditions at the site which are different from those anticipated by the bidder.

(c)(1) Notwithstanding the provisions of subsection (b) of this Code section, the department reserves the right to make, at any time during the progress of work, such increases or decreases in quantities and such alterations in the details of construction as necessary or desirable to satisfactorily complete the work. Such increases or decreases shall not invalidate the contract nor release the surety and the contractor agrees to perform the work as altered.

(2) Whenever an alteration materially increases or decreases the scope of the work specified in the contract, a supplemental agreement acceptable to both parties shall be made. In the absence of a supplemental agreement acceptable to both parties, the department may direct that the work be done either by force account or at existing contract prices. Any force account agreement shall be in writing, specifying the terms of payment signed by the chief engineer, and agreed to in writing by the contractor.

(3) Changes made by the engineer will not be considered to waive any of the provisions of the contract, nor may the contractor make any claim for loss of anticipated profits because of the changes, or by reason of any variation between the approximate quantities and the quantities of work as done.

(d) The provisions of subsections (b) and (c) of this Code section shall be applicable only to federal-aid highway contracts.