Proceedings of the 6 th International Mining and Industrial Waste Management Conference, 29, 30 & 31 October 2018 – Legend Golf and Safari Resort, Limpopo 1 A Review of Freeboard Criteria for Tailings Dams Y.Narainsamy 1 1 Jones & Wagener, Johannesburg, Gauteng, narainsamy@jaws.co.za Abstract Freeboard is one of the most important aspects to maintain and control on tailings dams to ensure safety. Designers often ignore site-specific conditions and do not specify a design freeboard. In lieu, it is common practice to specify regulatory freeboard. These requirements often simply define a storm event to impound (typically a 1:50 to 1:100 year, 24-hour event) plus an additional 0.5 m to 1 m. This approach is fundamentally different to best practice related to water dams where freeboard is assessed by considering extreme storm events as well as secondary aspects such as wave run-up, seiches and surges. This paper compares the nominal regulatory and design freeboard requirements for high-risk tailings dams with the aim of determining if the nominal freeboard allowances are adequate or under-specified. This paper concludes that, for high-risk facilities, the regulatory freeboard consistently underestimated the freeboard requirement and that design freeboard criteria should be considered. Keywords: Freeboard, tailings dams, 1 Introduction There are numerous guidelines available for the determination of freeboard requirements. The authors believe that these requirements can fundamentally be grouped into two categories: regulatory freeboard and design freeboard. Regulatory freeboard is where various storm events are specified and the facility must be shown to be able to fully impound these storms while at all times maintaining a nominal additional freeboard above the maximum water elevation. These regulations do not consider the hazard rating of the structure and are a seemingly conservative approach. Design freeboard on the other hand is based on the hazard classification of the structure. This way there is a clear distinction between the requirements for a low risk and a high-risk facility. 2 Categories of Freeboard 2.1 Regulatory Freeboard In South Africa, freeboard for tailings dams is governed by two pieces of legislation: General Notice 704 (GN704) of the National Water Act (Act 39 of 1998) and General Notice 527