Puddling (civil engineering)

Starting about 1840 puddle clay was used more widely as the water-retaining element (or core) within earthfill dams, particularly in the Pennines.

A considerable number of early notable dams were built in that era and they are now sometimes referred to as the 'Pennines embankment' type.

These dams are characterized by a slender vertical puddle clay core supported on both sides by earthfill shoulders of more heterogeneous material.

To control under-seepage through the natural foundation below the dam, the Pennines embankments generally constructed a puddle clay-filled cutoff trench in rock directly below the central core.

The clay is laid down with a tool called a 'punner', or 'pun', a large rectangular block on a handle about 5 feet (1.5 m) 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).