SUMMARY: REMEDIAL ACTION
Unit V provided general considerations for selecting remedial actions to alleviate seepage
conditions. This unit also described emergency and temporary seepage measures, as well as
permanent seepage measures.
Emergency and Temporary Seepage Measures
Temporary seepage control measures are generally initiated when a seepage condition exists
that, if not immediately corrected, may quickly deteriorate to a critical condition requiring
emergency action. Generally, there are two major courses for quickly alleviating a seepage
problem:
• Reduce the hydraulic head and pressure causing the problem by lowering the reservoir
and restricting reservoir levels.
• Control the exits of the seepage by constructing a weighted filter, or constructing
sandbag or other types of ring dikes around the exit point.
Emergency seepage control measures are initiated when signs of seepage indicate imminent
danger. Signs of serious seepage conditions include a whirlpool in the vicinity of the dam, sand
boils, and sinkholes.
Permanent Seepage Measures
Permanent seepage control measures are used when the seepage condition is not an imminent
threat to the safety of the dam, and sufficient time is available to design and construct a longterm
remedial measure.
Permanent seepage control measures include:
• Monitoring the seepage and seepage control measures.
• Lowering the reservoir and restricting the reservoir level.
• Pressure grouting to penetrate and seal cracks and voids in the area, thus blocking
seepage paths.
• Constructing cutoff walls.
• Constructing an impervious blanket immediately upstream of the dam.
• Constructing a weighted filter/berm downstream of the dam.
• Installing drains, filters, and relief wells.
• Providing drainage.