Page - 1340 - in Book of Full Papers - Symposium Hydro Engineering

quality”. It is important to note these only pertain to dams with a safety risk. A “dam with a safety risk” is defined as a dam with a storage capacity of more than 50 000 m3 and a vertical height of equal to or more than 5 m. This definition of height differs from the ICOLD definition – the height is measured from the lowest natural bed level at the downstream toe of the dam wall to the non-overspill crest. Smaller dams that do not satisfy these requirements do not form part of the dam safety legislation. It is of extreme importance to note that these dams, however, still have to comply with water use and environmental legislative requirements. The authority of dam safety lies with the Minister of Water and Sanitation (DWS). The Minister is assisted with the regulation of the dam safety legislation by the Dam Safety Office (DSO) which forms part of DWS (as designated by the Director-General of DWS) – one could call the DSO the regulator in South Africa. The Minister is also assisted by the Engineering Council of South Africa with the approval of appropriately qualified and experienced professional persons (Approved Professional Persons - APPs) to perform tasks at dams with a safety risk. The mandatory involvement of APPs for all tasks carried out at certain categories of dams is one of the important principles of the dam safety legislation in South Africa. As in other countries that also had their major dam development in the 20th century, South Africa is experiencing a rapid decrease in the number of available APPs as the majority have either reached and are close to retirement. This is a major area of concern. One of the founding principles of Dam Safety in South Africa and the rest of the world is that dam owners are responsible for the safety of their dams (the term “dam owners” also includes operators). It is therefore the responsibility of dam owner/s to register their dam with a safety risk with the DSO (including all new or planned dams). Once the registration information is received, the DSO would then classify the dam into one of three categories which determines the required level of control at that particular dam. The classification is based on the size and the hazard potential rating of a dam. The size class is determined by the maximum wall height. The size classification is given in Table 1. It is important to note that in many cases the classification date could be different from the registration date. Table 1 Size classification (using the South African definition for height) Size class Maximum wall height (m) (from the river bed level to the highest point of the dam) Small < 12 m Medium ≥ 12 m but < 30 m Large ≥ 30 m The hazard potential is based on an assessment of the potential loss of life (PLL), potential economic loss (PEL) (with respect to downstream development) as well as the potential adverse impact on resource quality (PIRQ) that may result from failure of a dam. In determining the hazard potential rating the PLL, PEL and 1340