SMALL DAMS PETITS BARRAGES

Depending on the PHC – Potential Hazard Classification, the following frequencies are
recommended for small dams.
Table 6.2 – Formal inspection for small dams
PHC (*) H 2 .V 1/2 Life Safety
Risk 1
Period
st Filling 1 st Year Operation
1 < 20 ~ 0 6 – monthly yearly each 10 years
2
≥ 20 and
< 200
< 10 3 - monthly 6 – monthly each 8 years
(*)PHC - Potential Hazard Classification (See Appendix I)
· Special Inspection
Special inspections are those required immediately after major storm or earthquake
event. Following the routine like this should enable the dam owner to become aware of faults
before partial or total failure occurs. Times when inspections additional to those above are
recommended are:
Before a predicted major rainstorm (check embankment, spillway and outlet pipe);
During and after severe rainstorm (check embankment, spillway and outlet pipe);
During and after a severe windstorm (check upstream slope for damage from wave
action);
After any earthquake or tremor; whether directly felt on the owner’s property or
reported by local news media (check all aspects of the dam).
6.3.2 Dam Inspection and Performance Evaluation
In order to facilitate the inventory of potential incidents, defects and problems for small
embankment dams, a list is presented at the Appendix II with the usual problems usually
observed.
The persons involved with the routine inspections should be trained about what are the
indicators of each of these deteriorations, what are their possible causes, what are their
degree of deficiency and their potential effects over the dam performance. All important
deficiency should be registered through adequate photography and with an adequate survey,
in the case of a spring or sinkhole, by instance.
The degree of an incident, deficiency or defect which may occur in a dam is classified as
minor, serious or very serious. An incident which may either reduce stability of the dam below
acceptable limits or lead to an unsafe situation is classified as serious or very serious.
For a particular dam each defect has to be considered together with others and on a
site-specific basis, in order to evaluate its probable impact on performance of the dam.
The external surface of an embankment dam can often provide clues to the behaviour of
the structure. For this reason a thorough examination of all exposed surfaces of the dam
should be made. The embankment should be carefully examined for any evidence of
displacement, cracks, sinkholes, springs and wet spots. Any of these conditions may be in a
developing mode and, if they worsen and are not corrected, ultimately could lead to failure of
the embankment.
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