Higher than Normal Tides Lower Vertical Clearance at Hwy 802/McTeer Bridge, Beaufort, SC, AICW Statute Mile 540
Posted by Larry Dorminy | Posted on 12-12-2012
The moon and higher than normal tides this year have been causing problems for our tall masted friends. There are tide gauges missing from a number of bridges in NC and SC. The Coast Guard Chief of Operations of Bridge is aware of the missing boards and hopefully, they will be replaced and/or corrected soon! In the meantime, keep an eye on the tide tables for the particular area and proceed with caution at mid-tide through all the fixed height bridges.
The notices to report damage posted at most bridges generally refers to damage occurring to the bridge – usually the fender system – and not, unfortunately, for damages to vessels.
NO GAGE ON THIS BRIDGE FOR HEIGHT.
We were told by Port Royal Landing that there was only 63 foot of Clearance at High Tide on 12-12-12.
(There is a notice to report bridge damage.)
With a phone number???????
We passed through this bridge on 12/7/2012. No tide gauges. Most of the sixth fenderboard was showing above the water (we were told that if the top of the fifth was showing there was 65′ 5″ of clearance). Predicted tide at the Beaufort Island tide station then was +1.2 feet. Out 66′ tall antennas passed under the bridge without touching.
The critical piece of information that’s often hard to come by is the relation of tide height (relatively easy) to MHW. MHW for a location is printed on some smaller-scale charts, but I haven’t seen it presented by chartplotters or applications (e.g. Wxtide32). We can get MHW indirectly from the NOAA Tides & Currents Datums pages. Careful though! The tabulated numbers are not based on MLW or MLLW, but on “station datum” so there’s a little extra math. But it sure would be useful to have something more portable that doesn’t require Web access.
There’s no substitute for ACCURATE clearance boards, though.
As a footnote, with a mean sea level rise per annum of about 2mm, a bridge built 50 years ago at 65′ clearance would have lost about 4″ of that.