Wet wall in a blast hole is a condition where there is water running on the blast hole walls above the toe or any other standing water.

This is generally related to the water table being above the toe or to perched water tables. The water does not accumulate resulting in standing water, there is a discharge path.

The main issue with wet walls is that they difficult to identify. The only way is for the blast crew to examine the dip rope after each hole and check if the tape is wet above any identified standing water. Consequently the dip rope must be dried (usually by dragging in dust) before each hole.

Where non-water-resistant explosives are loaded it is essential to identify wet walls to prevent product erosion and slumping.

Wet walls are measured from the toe of the hole to the highest wet area. Note that wet walls can not be less than standing water.

Example. The blast crew member records a 30m hole with 2m standing water but notices the tape is wet on the bottom 5m. This hole has 5m wet wall.