A loud siren warning of a tailings dam breach should be the last line of defense. We should not rely on it alone, but if all goes wrong it may be the difference between life and death. Accordingly, and in conjunction with RST Instruments from Maple Ridge, BC, Canada, SRK has developed a new, cost-effective system to trigger an alarm at the onset of an earthen dam breach.
Leading practice in tailings dam surveillance focuses on verifying whether performance and risk management objectives are being met. This practice is based on the premise that the early identification of deviations to expected dam performance will mitigate dam safety risks by allowing adequate time for the implementation of effective remedial actions. However, while putting effort into monitoring performance and identifying early signs of dam failures is recommended, some of the latest catastrophic tailings dam failures have demonstrated that in many cases information related to the root cause of the dam failure was available, but was either not understood or not interpreted in a manner leading to early warning alarms being raised. Many owners are therefore looking for a “last line of defense”—a system that can trigger an alarm and warn downstream populations of an occurring dam failure in hopes of preventing loss of life.
Unfortunately, many tailings dams are currently at unacceptable risk of failure and the associated risks must be mitigated and managed. The most effective means of alleviating a potential for loss of life is to relocate the population at risk. A supplementary strategy, if relocation is not possible or feasible, is to implement a siren system that will warn the population within the flood area that a dam has breached.
Nowadays, the majority of dam emergency siren systems are activated by a dam operator upon visual confirmation of a dam breach. Reliance on human intervention alone can result in a delay in triggering the alarm or, in the worst case, the alarm may not be triggered at all. SRK, together with RST Instruments, has designed and developed a simple and practical system that will set off a siren. The system comprises of several wire circuits buried in the dam crest that are connected to a datalogger, which is installed outside the dam embankment on natural ground. The datalogger verifies, at a very high frequency, whether the circuit remains uninterrupted and the wire is installed such that it will break immediately if the dam crest is mobilized due to a dam failure, causing the signal to the datalogger to be interrupted and the siren, in turn, to be triggered.
Our dam breach detection system is currently being installed in several high-risk tailings dams. The owner of these dams has relocated the populations most at risk and agreed with surrounding communities to implement the system as a last line of defense while the dams are being stabilized.
