What is a spud pole?
A spud pole, or simply spud, is a steel post that a vessel such as a pontoon or dredger lowers into the waterbed to hold itself in a fixed position. It works like an anchor, but vertically: the pole is lowered mechanically or hydraulically, penetrates a short way into the bed and is raised again after the work. Spud poles are mainly used in shallow water. The Dutch call it a spudpaal.
How it works
- Holding position without anchor lines. Instead of anchors with chains or ropes, the vessel stands directly on poles in the bed. This is quick and takes up little space.
- More poles, more stability. A pontoon on two or more spuds is steadier than on one. That matters when a crane on the pontoon is lifting heavy loads.
- Walking on spuds. Some work pontoons move by alternately raising and lowering their spuds. During the renovation of the Afsluitdijk, the Dutch barrier dam, such a “walking” pontoon was used to place concrete blocks on the embankment slope.
- Leisure craft. Yachts and boats also use spud poles, sometimes telescopic, to moor quickly, for example while waiting at bridges and locks.
Application
- Know the bed. In soft soil the pole sinks deep and holds less; on hard sand or stone it hardly penetrates. If in doubt, obtain soil data.
- Watch for cables and pipes. Before lowering spuds, check whether cables, pipelines or bed protection are present. A pole can damage them.
- Allow for the water level. With changing water levels or tides, the pole must be long enough and the vessel must be able to slide freely along it.
- Take care in waves. Violent motion, especially at sea, puts heavy loads on the poles and their housing and can, in rare cases, break them. Raise the spuds in heavy seas.
Common mistake: carrying out heavy lifting from a pontoon held by a single spud. The pontoon can rotate around the pole and the load starts to swing.
Related terms
- Bucket ladder dredger
- Pontoon bridge
- Bank protection
- Sheet pile wall
- Canal lock
- Ground anchor
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