2022- Tailings Dam Resilience Through Design and Responsible Management: A Case Study

Michelle Black – Senior Geotechnical Engineer WSP, Robert Kingsland – Technical Executive – Geotechnics, WSP, Andrew Russell – Principal Civil Engineer WSP

The tailings dam which is the focus of this paper is an active coal tailings dam on an underground mine site in the Lake Macquarie area in NSW. This case study demonstrates how designers working closely with owners can overcome operational challenges while always working toward responsible closure.

The dam consists of a zoned earthfill embankment with a vertical filter and horizontal finger drains. The dam has a total operational capacity of 5,316 ML and a High A Consequence Category. Construction of the dam commenced in 2006 and the dam has been raised in several stages. Between 2007 and 2011 several significant weather events resulted in accumulation of rainfall runoff on the dam which proved difficult to remove quickly as other water storages on site were also at capacity.

As a result of water accumulating on the dam, sinkholes appeared in the tailings storage area due tocollapse of old, shallow underground mine workings which were identified under the storage area and part of the embankment. Subsequent investigations and assessments were completed which demonstrated the tailings storage facility was robust, and with appropriate management of the tailings discharge process and surface water, the dam could continue to operate safely.

The incorporation of intercepting filters in a robust design coupled with exemplary management of tailings deposition provided resilience in the facility so that when the unexpected happened, such as emergency water storage and mine subsidence potholes, the owners were able to manage these challenges effectively
and without adverse outcome.

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