Luckily, some of the older opening bridges have been replaced by fixed spans recently. The official lower limit for fixed bridges is 65 feet, but several have been reported below specifications by waterway cruisers. We have noted these low bridges in Appendix A of the chartbook. These bridges may have less than 65 feet of clearance when wind driven water levels or tides are unusually high. We have received multiple reports of these bridges having less than 65 feet of clearance at certain times.
Many bridges have clearance gauges attached to the wooden fendering at their bases.
The gauges are designed so the fluctuating water levels will give a true reading as to the available clearance under the bridge. These gauges appear to be accurate, but prudence suggests giving yourself a couple of feet to spare when in doubt. The law prohibits boats from requesting unnecessary bridge openings. Boats with easily lowered antennas, outriggers, biminis, or other appurtenances must take them down. Bridge tenders have become stricter on this matter in recent years.