(a) If it is necessary to build a bridge or culvert across or over a state highway located in a county having a population of more than 350,000 inhabitants, according to the last preceding federal census, the board may construct or assist in constructing the bridge or culvert.
(b) After the bridge or culvert is constructed, the board may pay or may join with any county or other governmental agency or subdivision to pay the expenses of making necessary and needed repairs. The expenses shall be paid from the funds of the district.