Puddling (engineering)

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New puddle lining to the sides of a restored section of the Montgomery Canal at Redwith Bridge. A huge plug of puddle clay tempoarily blocks the end of the canal

Puddle is a watertight (low hydraulic conductivity) material based on clay used in building and maintaining canals or reservoirs. Puddling is the process of lining the channel with puddle.

Clay or heavy loam is chopped with a spade and mixed into a plastic state with water and sometimes coarse sand or grit to discourage excavation by moles or water voles. The puddle is laid about 25 cm thick at the sides and nearly a metre thick at the bottom of a canal, built up in layers. Puddle has to be kept wet in order to remain waterproof so it is important for canals to be kept filled with water.

The clay is laid down with a tool called a punner, or pun, a large rectangular block on a handle about 5 feet long, or trodden down, or compacted by some other means (e.g. by an excavator using the convex outside of its scoop, or, historically, by driving cattle across the area).

[edit] References

Waterways in the Making, Edward Paget-Tomlinson, The Landscape Press, 1996, ISBN 0-947849-03-0
The Illustrated History of Canal and River Navigations, Edward Paget-Tomlinson, Landmark Publishing Ltd., 2006, ISBN 1-84306-207-0