Some dams have small seep of water, observed under our naked eyes and water seeps without any seepage materials for years and then seepage materials emerged with gradual increment; this process continues until a rapid failure of dam or its foundation is occurred.
Dear reader we have already learnt about piping through foundation and embankment both in homogeneous and zone dam which will lead to total failure of dam. Here our concern is existing and development leak.
The leaks which result piping failure are of various size and wide range of rate of development. In some dams leaks are observed immediate after filling of reservoir for the first time. But in some cases they are seen after several years of satisfactory leak free (intact) operation.
In case of muddy and large leak, leak is followed by complete failure within few hours or days. It is worth mentioning that muddy leak means seepage water carries mud to downstream portion of earth dam. These types of leaks are usually considered alarming for earth dam.
Is muddy seepage water always dangerous to dam or foundation?
Sometimes the bedrock has cracks which are filled with mud. This mud may flow out to downstream side when the reservoir is first filled with water. These types of seepage are a temporary flow and considered not dangerous.