A county is prohibited from negotiating a contract except a contract:

(1) Involving the expenditure of less than $20,000.00;

(2) With a state agency or county or municipality with which a county is authorized to contract in accordance with the provisions of Code Sections 32-4-61 and 32-4-62;

(3) For the purchase of those materials, supplies, and equipment necessary for the county's construction and maintenance of its public roads and for the support and maintenance of the county's forces used in such work, as authorized by Chapter 91 of Title 36;

(4) Subject to Article 6 of Chapter 6 of this title, with a railroad or railway company or a publicly or privately owned utility concerning relocation of its line, tracks, or facilities where the same are not then located in a public road and such relocation or grade-crossing elimination is necessary as an incident to the construction of a new public road or to the reconstruction or maintenance of an existing public road. Nothing contained in this paragraph shall be construed as requiring a county to furnish a site or right of way for railroad or railway lines or tracks of public utility facilities required to be removed from a public road;

(5) For engineering or other kinds of professional or specialized services;

(6) For emergency maintenance requiring immediate repairs to a public road, including but not limited to bridge repairs, snow and ice removal, and repairs due to flood conditions; or

(7) Otherwise expressly authorized by law.