Erie Canal route: New Genesee fermentation tanks going the old fashioned way.

We haul'd some barges in our day
Filled with lumber, coal, and hay
We know every inch of the way
From Albany to Buffalo.

Bruce Springsteen - Erie Canal Song

The Rochester NY Genesee brewery opened bidding for new fermentation tanks.  A Chinese company got the job.  The problem was how to get them to Rochester - they were too long for the interstate highway system: but not too high for the low bridges on the Erie Canal.  But a technical problem remained: only one barge could fit in a lock.  One solution- two tugs - meant undesirable expense.  Coeymans Marine Towing got the job - and the solution: double locking.   Will vanDorp of Tugster explains:

It's called double locking.  Tug pushes tow 1 + 2 (front to back) into lock; crew steady 1 inside chamber and then uncouple tows 1 from 2; tug "backs out" of chamber entirely with tow 2.  when lock raises tow 1 to upstream level, canal infrastructure capstan moves tow 1 to the wall above the lock and crew secures it.  lock chamber is drained and tug pushes in with tow 2, which is then raised.  When tug and tow 2 are at upper water level, they maneuver in behind tow 1 and remake the entire tow, which is then moved to the next lock and the whole process is repeated.