S.C. Code Ann. § 12-28-2740
(A) The proceeds from two and sixty-six one-hundredths cents a gallon of the user fee on gasoline only as levied and provided for in this chapter must be deposited with the State Treasurer and expended for purposes set forth in this section. The monies must be apportioned among the counties of the State in the following manner:
(3) one-third distributed in the ratio which the mileage of all rural roads in the county bears to the total rural road mileage in the State as shown by the latest official records of the Department of Transportation. The Department of Revenue shall collect the information required pursuant to Section 12-28-1390 regarding the number of gallons sold in each county for use in making allocations of donor funds as provided in subsection (H). The Department of Revenue shall submit the percentage of the total represented by each county to the Department of Transportation and to each county transportation committee annually by May first of the following calendar year. Upon request of a county transportation committee, the Department of Transportation shall continue to administer the funds allocated to the county.
All interest earnings on the County Transportation Fund in the State Treasury must be added to the distribution to counties under this section in proportion to each county's portion of the entire County Transportation Fund. Except for those funds being used in connection with highway projects administered by the Department of Transportation on behalf of counties administering their own "C" funds, these distributions of earnings and the calculation required to determine the appropriate amount shall not include those counties administering their own "C" funds.
(I)