I take the NOAA charted clearances with more than a grain of salt. We tend to think of bridges as wonderful fixed construction projects. However, many older bridges may have subsided and have less than stated clearances.
I tend to trust the clearance boards but add a safety factor. FYI, some bridges have more clearance a span or two out of the channel. For instance, according to local "knowledge", the bridge at Navarre Beach, FL has a foot or two more clearance two spans south of the charted channel. This is due to the design of the bridge. The metal girders supporting the roadway in the three center spans are several feet thick because the spans are wide. Away from the charted channel, the spans are short. Those spans are supported by shorter concrete T girders. The shorter girders allow more clearance. Passing under a bridge outside the charted channel incurs risk. You really don't know what the air clearance is and you don't know if there's good depth. I've never done it. -- Dennis C. Touche' 35-1 #83 Mandeville, LA On Tue, Mar 23, 2021 at 9:24 AM Andrew Burton via CnC-List < cnc-list@cnc-list.com> wrote: > Charles, what sources are you using for the C May bridges? NOAA charts > list them as 55’ at high water. > Andy > > Andrew Burton > >
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