Up Your Bridges
By Margaret Graham Neeson, 91 years young, Marine Parts Express
A cartoon was published several years ago that remains a favorite with the yachting world. It showed a fat family of three in a very small sailboat, looking pleased and proud as they sailed gloriously along a river, through an open drawbridge, while a long line of automobiles and their discomfited passengers waited, perforce, on the blocked-off highway.
This lovely scene (lovely to boat-owners only, of course) is not so frequent as it once was due mainly to the general revamping of highways and railroads. Bridges, nowadays, are built to clear even large rivers at one jump, going ever higher to do so. To take New York bridges alone, as an example, back in 1883, Brooklyn Bridge set a new standard in clearance by crossing the East River 135 feet above the water. In 1931, George Washington Bridge made a vertical clearance record of 260 feet. The spectacular new Verrazano-Narrows center span has close to 325 feet of clearance.
These bridges are all of the high-flying suspension type, but what is true of them is, to a lesser extent, true also of other fixed bridges, whether they be cantilever, beam, or arch.
But there are still lots of movable bridges around. And although they are the lowest of the low (in design as well as in fact, say the bridge builders) they have a noble purpose. Whether built on difficult terrain, or as part of a less-traveled highway or railway, or for temporary use, they perform an important extra function: they not only cross the river, they keep it open to navigation as well.
They have to. That is the law. Under Article 1, Section 8, Clause 3, of the Constitution, Congress has the right to regulate interstate commerce, and one way it exercises that right is to state that “It shall not be lawful to construct . . . any bridge, dam, dike, or causeway over or in any port, roadstead, haven, harbor, canal, navigable river, or other navigable water of the United States” without the consent of Congress. As a practical matter, Congress leaves it up to the Secretary of the Army (formerly the Secretary of War) and the Corps of Engineers to decide where bridges may be built.
Generally speaking, and despite some bitter legal contests, the authorities have decided in favor of the ships and boats, at least to the extent of making the bridges either high or with movable spans. As one judge put it, a navigable river “is a stream such as will permit and bear the passage of ordinary boats of commerce upon the bosom of its waters.” Another judge was more succinct. He said, “It is a fact that a river is more than an amenity; it is a treasure.”
Congress has also given to the Secretary of the Army the authority to make rules and regulations governing the opening of drawbridges. By far the majority of these are attended, but particularly in secluded areas, there are great numbers of unattended bridges, requiring advance notice.
The rules governing attended bridges differ and change from locality to locality, so that every wise yachtsman consults his Coast Pilot to check on the regulations in his area.
A summary of the most used standards would include:
Three blasts of whistle or horn (or three calls through a megaphone or three strokes of a bell) from the boat wanting to pass through when a “reasonable distance” from the bridge.
An answering three blasts from the draw tender when all is well and he can open the bridge.
Four (sometimes two) blasts from the tender when he cannot.
In stormy weather, when sound will not carry, flag signals shall be used by day, lights or lantern by night. The boat shall signal by swinging flag or light in circles; the tender shall signal by raising and lowering his flag or light in a vertical plane if he can open the draw, horizontally if he cannot.
Every boatman has a recurrent nightmare in which the draw is not opened in time and his craft goes smash, and many have horror stories to tell of delinquent tenders.
Most bridge tenders feel about their bridges the way boatmen feel about their boats. They are as anxious as the captain for the boat’s passage through the draw to be accomplished safely.
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September 16, 2010 / mpartsexpress / 0
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Margaret Graham Neeeson
Margaret Graham Neeson
Marine Parts Express