S.C. Code Ann. § 57-13-40

The commission may permit any person, county or municipality, or any combination thereof, to construct toll bridges and appertaining structures suitable for highway traffic on any roads of the state highway system. But before any such permit is issued an agreement satisfactory to the Department of Transportation must be executed by the person receiving such permit fixing conditions under which the bridge is to be constructed, the character and design of the structure, the rate of toll to be charged traffic using it and the terms according to which it can be acquired by the State or counties concerned.