Now that spring is just about here and boats begin moving in all directions, I think it appropriate to address a question that comes up even with experienced boaters who just may not have to deal with bridges very often. For anyone soon coming north on the ICW or doing some inland waterway travel, however, this will be a part of the daily routine.
What exactly does a stated bridge clearance mean? When a bridge clearance height is listed in a cruising guide or on a sign at the bridge, is that stated measurement for the lowest point of the span (such as the outer ends of the span for opening bridges), or the middle of the span, which is typically higher?
I once asked for clarification of this from the late Mack Maloney, the legend behind Chapman’s for so many years. He was a world-class expert on nautical terminology and the rules of boating. His response:
The Coast Guard regulations require that the minimum clearance be shown—this is the clearance at the sides of the navigable area, usually at the fender system (see33 CFR 118.160). Many bridge owners add a sign “Additional clearance x feet at center.” This is not required, but serves to reduce the number of unnecessary openings.
There are many bridges that are incorrectly marked, usually with a sign “Clearance at center” or sometimes no sign at all. I have made it a routine matter for me to report to the 7th Coast Guard District all bridges that I have seen that are incorrectly marked. They have been very cooperative and I have a good relationship with them.
Quite a few bridges have been re-signed as a result of my reports!—Elbert “Mack” Maloney.
Have a great week, everyone.