S.C. Code § 57-3-680
If any such project to be constructed under the provisions of Section 57-3-670 is not a part of the state highway system, no part of the actual costs of rights-of-way, construction, or maintenance shall be paid for from state highway funds. Any political subdivision having jurisdiction over a project not a part of the state highway system shall deposit with the department its estimated share of the cost of such project before the contract is awarded, except that state highway funds may be advanced to meet current payments to contractors and others when existing agreements provide for reimbursements by the federal government of such funds advanced by the department. Article 13 of Chapter 5 of this title shall not apply to any project that is not a part of the state highway system.
S.C. Code § 57-3-680