Your Dam Your Responsibility (PDF~1.2MB)

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6 Safety Surveillance 6.1 Purpose of Regular Inspection The purpose of a dam safety surveillance program is to avoid failure of the dam, by giving early warning of any kind of symptom of trouble as early as possible. The main causes of failure, which can often be avoided by effective surveillance and maintenance programs, are: • seepage/leakage; • slips/slides • erosion; • cracking; • movement/deformation of embankment; • structural defects (ie outlet pipes, spillway); and • spillway or outlet blockage. 6 Note that in some cases, the preparation and carrying out of a regular program of safety surveillance may be a condition of a licence. This is especially true for dams classified as potentially hazardous, but it also represents not only good practice but sound insurance! Safety surveillance of a dam is a program of regular visual inspection using simple equipment and techniques. It is the most economical and effective means an owner has of maximising the long-term safety and survival of the dam. Its primary purpose is to monitor the condition and performance of the dam and its surroundings, particularly any changes that may be occurring. Potentially problematic trends can thereby be spotted early and provide adequate warning of their development so that timely maintenance can be carried out. You should always check the water level and spillway flow performance for any unusual changes. It is an advantage to use an engineer experienced with farm dams as they are more familiar with problems and can provide better security against legal action in the event of a dam problem impacting on others. Embankment slip due to poor construction PHOTO COURTESY OF J WHITEWOOD 27
28 6 6 Safety Surveillance 6.2 Inspection Procedures and Methods The procedure for dam safety surveillance is unique to each dam but consists essentially of regular, close and systematic examination of the entire surface of the dam and its immediate surroundings. Such procedures are already normal practice in the case of large dams. In the case of small dams, however, especially farm dams where owners have not sought appropriate advice, there may be a perception that the above procedures are unnecessary, or an unproductive use of time. There may also be a lack of knowledge of what needs to be done. However, for small dams, surveillance programs can usually be devised which are simple yet systematic and effective. A safety surveillance inspection includes taking appropriate measurements and keeping concise accurate records of observations made. Particular techniques and equipment that might be used are outlined in Appendix A. For small dams it is prudent to obtain the advice of a suitably qualified engineer to set up the program first, using a simple set of pro-forma check sheets to record observations. They are just as sensible – in fact much more so, given the potential for costs to you if it fails – as having your car checked and serviced regularly, even though you do not think the car is about to give up on you yet! These procedures form part of a dam safety management program and are intended to catch problems early and enable action to be taken to prevent them developing further, once detected. 6.3 Frequency of Inspections The frequency of inspection required for an effective program of surveillance depends on a variety of factors including: (a) size or capacity of the dam; (b) condition of the dam; and (c) potential for damage resulting from failure of the dam (represented by the hazard category). Adoption of the inspection frequency for a particular dam is the responsibility of the owner, though professional advice should be sought for large dams (ie. typically for dams larger then 15 metres in height) or those suspected of being of a high risk or hazard category. Suggested inspection frequencies are given in Table 6.1 but where licence conditions require a surveillance program certified by a suitably qualified engineer the frequency specified by the engineer shall be complied with. As a guide, Table 6.1 gives suggested frequencies for a two-level surveillance program. The higher level would comprise a full inspection using the relevant equipment and techniques outlined in Appendix A. The second level is envisaged as a more frequent quick visual inspection aimed at detection of unusual changes during the period between thorough examinations.
Page 1 and 2: Irrigation and Commercial Farm Dams
Page 3 and 4: ii Published by the Victorian Gover
Page 5 and 6: iv Contents 6 Safety Surveillance .
Page 8 and 9: 1 Introduction It makes good busine
Page 10 and 11: 2 Risks Posed by Dams 2.1 Owner’s
Page 12 and 13: 2 Risks Posed by Dams The most comm
Page 14 and 15: 2 Risks Posed by Dams 2 Note: The r
Page 16 and 17: 3 Licensing Requirements for Farm D
Page 18 and 19: 3 Licensing Requirements for Farm D
Page 20 and 21: 4 Planning to Build a Dam It is imp
Page 22 and 23: 4 Planning to Build a Dam 4.3 Types
Page 24 and 25: 4 Planning to Build a Dam 4 2. Turk
Page 26 and 27: 4 Planning to Build a Dam becomes a
Page 28 and 29: 4 Planning to Build a Dam 4.6.2 Ext
Page 30 and 31: 5 Construction of a Dam Mixing tops
Page 32 and 33: 5 Construction of a Dam is inviting
Page 36 and 37: 6 Safety Surveillance QUICK VISUAL
Page 38 and 39: 6 Safety Surveillance 6 Warning: If
Page 40 and 41: 7 Operation and Maintenance of Dams
Page 48 and 49: 8 Dam Failure Emergency Section 8 i
Page 50 and 51: 8 Dam Failure Emergency Action 4. I
Page 52 and 53: 9 Decommissioning of Dams 9 The sit
Page 54 and 55: 10 Glossary of Terms Cut-off An imp
Page 56 and 57: 10 Glossary of Terms Monitoring Rec
Page 58 and 59: Publications directly relevant to f
Page 60 and 61: Appendix A A • probe - a ten-mill
Page 62 and 63: Appendix A Inspection Procedures Ge
Page 64 and 65: Appendix A A and the resistance to
Page 66 and 67: Appendix B 1. Seepage Problem Possi
Page 68 and 69: Appendix B Problem Possible Causes
Page 72 and 73: Appendix B 2. Cracking, Deformation
Page 76 and 77: Appendix B 3. Miscellaneous Problem
Page 78 and 79: Appendix B utlet Works and Concrete
Page 80 and 81: Appendix C The depth of the core tr
Page 82 and 83: Appendix C will be needed. In stabl
Page 84 and 85:
Appendix C The width of the dischar
Page 86 and 87:
Appendix C Other Pipe Details At th
Page 88 and 89:
D Figure C-4: Design guide for a fa
Page 90:
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