Seepage through foundation in an earthen dam is controlled by providing:

Explanation:

The seepage control measures are necessitated to prevent the adverse effect of water percolating through the foundation to the embankment.

Seepage is the movement of water through the foundation of the dam, which can result in the loss of stored water. A cut-off trench is constructed to reduce the seepage by providing a barrier that restricts the flow of water through the foundation. It is usually constructed using impermeable materials like concrete, clay, or plastic sheets, which prevent or minimize the seepage of water. By reducing the seepage loss, the cut-off trench helps in maintaining the required reservoir levels and ensuring the availability of water for various purposes.

The following devices are used to control seepage through an earthen dam:

Foundation seepage control:

• Impervious cut-off
• Upstream impervious blanket
• Downstream seepage berms
• Drainage trench
• Relief wall

Embankment seepage control:

• Toe filter
• Horizontal drainage filter
• Protective filter d/s of the toe
• Downstream coarse section
• Chimney drain extending upward into the embankment.

​Hence option (3) is the correct answer.