In this video @STSDiscovery will show you how to prepare of wall of precaution which called Coffer Dam.

A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out.[1] This pumping creates a dry working environment so that the work can be carried out safely. Cofferdams are commonly used for construction or repair of permanent dams, oil platforms, bridge piers, etc., built within water.

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