According to Dennis Sherer's story, "Cheap ride," "more than 50 million tons of cargo pass through the locks at Wilson and Wheeler dams each year."
What would it be like if the City of Florence began assessing a $1 per ton fee on all barge traffic through the area?
Why, it could even be 25¢ and it'd still be an excellent source of income.
Heck, even 10¢ would bring in $5,000,000 annually!
It's not as if assessments aren't made every day for use of public infrastructures by private enterprise.
Even big trucks (more accurately, their comporate owners) pay taxes to the states based on their use of the roadways.
Why not for waterways?