Your Dam Your Responsibility (PDF~1.2MB)

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Appendix A
Conducting an Inspection
To be able to conduct a thorough inspection of your own dam you may need to consult
a suitably qualifed engineer who will provide a good insight into what you should be
looking for and how to go about it. This would provide a procedure specific to your
dam. The following material is provided for your information to assist in understanding
inspection requirements.
Preliminaries
(a) Establishment of Reference Pegs
The purpose of an inspection as part of dams safety surveillance is to monitor performance
in such a way as to enable early diagnosis of potential problems. As mentioned in the text,
this includes such things as noting where cracks or leakage has formed and noting whether
there is any deterioration, and how fast or slowly that may be occurring. To enable such
monitoring to be reliable, and to facilitate the keeping of records, it is essential that there
be both a plan of the dam and a set of reference pegs, relative to which the location of any
observation or trouble spot can be pinpointed and recorded.
The degree of sophistication of the plan and of the reference peg system will depend
on the size of the dam, its type and its potential hazard category, and advice should
be sought on this first. However, as a bare minimum, irrespective of size of dam, there
should be established at least one key reference peg (the primary reference peg) at one
end of the dam. Remember that recording of locations will need to convey the level
(height) at each location as well as the distance along the dam length. The key reference
peg should be located at one end of the dam. It is preferably to place it at a level close
to the dam crest level, but securely in place so that it can be readily found and so that
it is unlikely to be knocked out or broken by persons, vehicles, plant or cattle. Ideally
a secondary reference peg should be located elsewhere as a backup, preferably at the
other end of the dam, with the distance away from the primary peg, and any difference
in height being measured and recorded. If the dam crest is not straight, or if there are
difficulties about this procedure, professional advice should be sought. With larger dams,
or dams classified as potentially hazardous, more sophisticated arrangements may very
likely be required, but for small and simple dams it is not essential that the position and
level of the reference peg(s) be precisely defined by a land surveyor. Similarly for the latter
dams the plan of the dam may not need to be precisely to scale, but there should be a
reasonably reliable means of ascertaining the height level of any observation made and
the distance of it from the primary reference peg.
(b) Equipment for inspection
The following items are useful when conducting an inspection:
• dam inspection check list – a reminder of items to be examined;
• notebook or diary and pencil – to write down observations at the time they are made,
thus reducing mistakes and avoiding reliance on the memory;
• camera – to provide photographs of observed field conditions. Colour photographs
taken from the same vantage points are valuable in comparing past and present
conditions;
• shovel – useful for clearing drain outfalls and removing debris;
• stakes and tape – used to mark areas requiring future attention and to stake the limits
of existing conditions such as wet areas, cracks and slumps for future comparisons;