Your Dam Your Responsibility (PDF~1.2MB)

Appendix B
Problem Possible Causes and
Potential Harm
Sinkhole in Crest Cause:
1. Internal erosion or piping
of embankment material by
seepage.
2. Breakdown of dispersive
clays within embankment by
seepage waters or rain.
3. Hole in outlet conduit
is causing erosion of
embankment material.
4. Rodent activity.
Harm:
1. A void within the dam
embankment could cause
localised caving, sloughing,
instability, or reduced
embankment cross section.
2. Entry point for surface
water, loss of soil leading to
instability of embankment
failure.
Low Area or Dip in Crest Cause:
1. Excessive settlement in the
embankment or foundation
directly beneath the low area
in the crest.
2. Internal erosion of
embankment material.
3. Foundation spreading toward
upstream and/or downstream
direction.
4. Foundation wind erosion of
crest area.
5. Improper final grading
following construction.
Harm:
1. Reduces freeboard available
to pass flood flows safely
through spillway and increases
risk of dam overtopping and
failure.
Action Required
B
Action:
1. Carefully inspect and
record location and physical
characteristics (depth, width,
length) of sinkhole.
2. A suitably qualified
engineer should determine
cause of sinkhole and
supervise all steps
necessary to reduce
threat to dam and correct
condition.
3. Excavate sinkhole, slope-sides
of excavation, and backfill
hole with competent material
using proper construction
techniques. An engineer
should supervise this.
Action:
1. Determine exact amount,
location, and extent of
settlement in crest.
2. A suitably qualified
engineer should determine
cause of flow area
and supervise all steps
necessary to reduce
possible threat to the dam
and correct condition.
3. Re-establish uniform crest
elevation over crest length
by placing fill in low area
using proper construction
techniques. Engineer should
supervise this.
4. Establish markers across
crest of dam and monitor
on a routine basis to detect
possible future settlement.
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