Operational control and trigger action response plans for TSFs routinely measure several operational aspects to assess risk and ensure the TSF complies with design considerations.
Cerro Vanguardia is an AngloGold Ashantiowned gold-silver mine in Santa Cruz, Argentina. The mine has a single TSF that has been in operation for over 20 years.
During the development and design of the seventh wall raise, the possibility to increase the usable storage capacity within the basin and defer the wall raise was identified. Ignacio Ezama and Santiago Pastine from SRK Argentina and in-house stakeholders concluded that sequential extension of the spigoting system into the TSF basin was the preferred option to take advantage of this storage capacity.
Key aspects affecting the potentially available capacity within the TSF, such as the beach angle, tailings density and water storage, were identified. A statistical analysis of each parameter was undertaken.
A probabilistic reassessment of the depth of rainfall events based on the rainfall dataset over the operating period was undertaken and intensity-frequency curves were obtained. This clarified uncertainties in water storage capacity needs and the associated risks.
A statistical analysis of the beach slope angle provided a better characterisation of the beach shape and its potential variance. The team estimated trendlines for the average beach slope angle and its standard deviations, and developed three theoretical beach profiles for use in the storage capacity assessment.
A statistical analysis of the tailings density was carried out based on available geotechnical samples. Longterm and short-term historical density scenarios were identified. The short-term density range was considered the most realistic for the analysis, while long-term data were considered for sensitivity.
For the capacity assessment, scenarios considering five successive spigot extensions into the tailings facility with varying lengths were developed. Volumetric storage capacity, time availability and the probability for reaching a given date with the available storage capacity were estimated.
Periodic monitoring was implemented to assess the ongoing operation. Potential for changes in the expected end of capacity were tracked and opportunities for
adjusting operational conditions and enhancing capacity usage were reviewed. In general, beach profiles resided between the average and best cases, allowing for an enhancement in capacity usage.
The statistical analysis contributed to an operational strategy to defer construction of the seventh wall raise for approximately two years without interrupting tailings deposition. During construction, operating procedures allowed risk to be assessed and ensured the TSF was in compliance with design considerations. The seventh wall raise of the TSF was finalised in February 2022.
