When the levy of a special tax has been authorized, the board of supervisors may advance to the permanent road division the division’s share of the cost of the improvements or the board of supervisors may determine to proceed with such work at such time as the estimated expense has been raised by taxes levied within the division.
Source:
Section 1178.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=SHC§ionNum=1178.5..