Tennessee Code Title 54. Highways, Bridges and Ferries § 54-9-139

(a) Under this chapter, any county in the state is authorized to issue bonds pursuant to title 9, chapter 21, for the purposes of grading roads, grading and macadamizing roads, grading and concreting roads, building complete concrete roads, building macadam roads with an asphalt surface, building bridges on roads, draining roads, or maintaining or reconstructing roads already constructed, or for any kind of standard road improvement or construction.

(b) The kind of improvement shall at all times be subject to the determination of the county legislative body and shall be approved by the department of transportation.

(c) All plans and specifications for the improvement of the roads or bridges shall be approved by the department.