S.C. Code § 57-13-100
All the work on bridges given out by the county supervisor and the governing body of the county shall be done by contract when the amount shall exceed the sum of ten dollars. When the amount shall exceed the sum of one hundred dollars, the county supervisor and the governing body of the county shall advertise the work in at least one of the papers in the county. When the amount is less than one hundred and more than ten dollars, the county supervisor and governing body of the county shall advertise the work by posting a notice in three public places, one of which must be at the place where the work is to be done, such notices to be posted ten days prior to the day on which the work is to be let.
A proposal to do any such work shall in all such cases be accompanied by two or more sureties when the amount thereof is in excess of one hundred dollars. The county supervisor and the governing body of the county shall have the right to reject any or all bids if in their judgment the interest of the county so requires.
S.C. Code § 57-13-100