If any special road and bridge district shall contain lands in more than one county, the amount of the bonded indebtedness of such special road and bridge district shall be, for the purposes of this chapter, apportioned between or among such counties in the proportion that the assessed valuation of the area of each county included within such special road and bridge district shall bear to the total assessed valuation of such special road and bridge district.
Fla. Stat. § 344.13