Tailings central thickened discharge; challenges faced and lessons learned from design to operation

Author(s): 
Pepe Moreno and Nicholas Thompson
Date: 
Friday, July 8, 2016
First presented: 
PASTE2016 Conference, Santiago, Chile, 6-8 July 2016
Type: 
Presentation
Category: 
Mine Waste

With the mining industry transitioning through a well-publicised downturn as a result of lower commodity prices and unstable macro-economic conditions around the world, mine owners have sharpened their focus on increasing operational productivity and minimising unnecessary capital expenditure. The management of tailings, already perceived by many as simply a cost to the mine, is one of the key areas targeted for savings. With constraints on water availability and costs associated with water, particularly in arid environments, thickened tailings disposal becomes an attractive scenario.

A central thickened discharge (CTD) tailings storage facility (TSF) was designed and commissioned at a phosphate mining operation in the Kingdom of Saudi Arabia. The design stage included comprehensive rheological and geotechnical characterisation of the tailings. The facility design was optimised for cost savings to store a specific thickened tailings product with a predicted beach slope profile and minimal supernatant pond, which influenced the perimeter embankment type and sizing.
 
However, subsequent operational issues with variations in thickener performance and tailings properties, combined with a disconnection from the design stage to the construction and commissioning of the TSF, led to an inconsistently segregating tailings product with a significantly increased volume of water sent to the facility and beach slopes that were flatter than designed.
 
This paper discusses the lessons learned from this project and the potential challenges and risks when there are large unforeseen variations in thickener performance and limited operator experience, which can lead to significantly more water to manage and reduced storage capacity compared to that designed. The paper also proposes key areas to focus on to mitigate against and lessen the impact of significant variations in the thickening process and tailings product sent to the TSF.

Feature Author

Pepe Moreno

Juan (Pepe) Moreno has more than 20 years of diversified professional experience in projects mainly associated with geotechnical/ geoenvironmental engineering for the mining and civil industries throughout South America, Southern Africa and Australasia.  Pepe is a recognised expert in the design of tailings management systems, heap leach pads, waste rock disposal and earth retaining structures. His geotechnical background also includes shallow and deep foundations, soil dynamic response and drainage. Pepe is typically involved as team leader conducting site selection, risk assessment, site investigation, laboratory analysis, slope stability assessment, foundation design, costing analysis, construction programmes, monitoring and data interpretation of diverse field instrumentation. Pepe provides expert review for tailings and waste management for due diligence and peer review projects for banks and potential investors.

Principal Consultant (Mine Waste)
Dip Professional Engineer (Civil), Civil Engineer (Peru), MIEAust CPEng, MAusIMM
SRK Perth
SRK North America