The various methods of seepage control currently in use for the design and construction of new
dams were described in Unit II. The remainder of this module will discuss the primary
considerations in the choice of remedial measures for existing dams. Some of the seepage
control devices discussed in Unit II would not apply as remedial action for existing dams. For
example, it may not be practical or economical to remove a major portion of an existing
embankment to construct an inclined or horizontal drain blanket. However, other measures can
be incorporated into an existing dam. Selection of the correct alternative should be left up to
an engineering firm with extensive experience in dam remediation, and extensive knowledge of
the site-specific conditions. The remedial actions described in this section include: