If there is big boat traffic on that river why did they put in a permanent structure? We are subject to tides where I live and most bridges are Draw Bridges or tower so high above the water it isn't a problem. One of our biggest bridge problems here is on land. A couple times a year some truck driver tries to drive his 18 wheeler under a train tressel or bridge that doesn't have the clearence and rips his rig open like a can of sardines. There are signs posted but for some reason the truck drivers either don't read them or don't believe them.