Open pit dewatering for complex copper mines in DR Congo

The Democratic Republic of the Congo (DRC) is one of the world’s best-known mineral-rich countries. Its mining industry plays an important role in supplying gold, cobalt, copper, tantalum and diamond to the rest of the world. In addition to having the largest cobalt reserves, the country is also Africa’s biggest copper exporter, producing 1.06 million mt of copper in 2019. Hydrogeek Consulting was tasked to support mining operations in the region through their groundwater modelling expertise. Using FEFLOW, they developed a 3D groundwater model to forecast water inflows to enable more efficient water management decisions.

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Challenge

To support mine dewatering for two copper mines in DRC, Hydrogeek Consulting needed to provide forecasts of the calculated inflows required to lower water levels in the main aquifer to a target preferably one bench below each mining level as mining progresses.
They also needed to provide the level of projected inflows required to lower pore pressure in less permeable formations, which do not drain as freely from the borehole abstraction system.

Solution

The mines are located in a complex geological environment. To tackle these challenges in the demanding locations, Hydrogeek Consulting used FEFLOW, the all-in-one groundwater modelling solution, to develop a robust and easy-to-understand 3D groundwater model to estimate transient mine inflow for the open pit mines.

The model capitalises on FEFLOW’s flexible meshing options and refinement to handle complex geology (three aquifers and four aquicludes) and dewatering wells. The model heads were calibrated based on historical abstraction from 13 dewatering wells over ten years with daily abstraction rates.

The project relied on the ability of the model to predict future groundwater and residual inflows. A combination of planned dewatering wells and horizonal drain wells were used, targeting the major aquifer outside the pit and lower conductive units. The aim of the model was to lower heads below mining levels.

Results

Successfully forecasted the
inflows needed to lower water level in the main aquifer

Calculated the projected inflows required to lower pore pressure

Provided meaningful observations to support future water management decisions

‘FEFLOW handled the complex geology and dewatering design with ease. The confidence the software gives makes it worth the effort, and yields trustworthy results. The fact that model can be revisited offers value to clients as a management tool.’

Nico van Zyl
Director, Hydrogeek Consulting

About the client

Hydrogeek Consulting is a consultancy company in South Africa specialising in hydrogeology and groundwater modelling. Their expertise includes interpretation of groundwater data to form conceptual hydrogeological models to support underground and open pit mine operations. Learn more: https://hydrogeekconsulting.com/

Software used

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