Technical Session: Operational Risk & Trigger Action Response Plans (TARPs)
Abstract
This paper discusses the importance of effectively linking Trigger Action Response Plans (TARPs) to risk assessments in the management of dams, embankments, natural slope and tailings storage facilities to enhance safety and prevent failures. It also points out to the need to use appropriate TARPs when dealing with fragile slopes, where failure can intervene with very small prior deformation. After summarizing a prior paper’s results which delivered a review of TARPs definition literature, a common practice disconnect between risk assessment and TARPs definition is shown to exist. Numerous reasons for this disconnect have been identified:
- If they are defined somewhat analytically, TARPs are linked to the “geomechanical side” of failures, but not explicitly to the consequences of those failures, hence missing the evaluation of risk.
- Oftentimes TARPs are defined long after a risk assessment is performed and are rarely explicitly linked to its results. The exercise is fraught by increasing uncertainties if the risk assessment is qualitative rather than quantitative.
- Linking TARPs to risk assessment requires the assessment to be quantitative. Obviously, this demands some more effort and goes against the tendency to perform qualitative assessments.
Furthermore, many techniques for the analytical definition of TARPs may encounter difficulties due to the short monitoring time span. In these cases, solutions exist, suggesting possible solutions either by using integrated remote monitoring, or advanced vulnerability analyses. Slopes prone to fragile failures (liquefaction) represent a special case, as they require the selection of adequate sets of TARPs. That is because in many cases classic instrumental deformation-based TARPs represent a futile effort due to the sometimes insignificant or difficult to detect prior deformations. Finally, a procedure to link the various TARPs defining techniques to risk assessment is described point by point with examples from real life.
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