Investigating MARs

Last updated: 4 February 2022

It may not be the cutest creature. But what the blind cave eel lacks in beauty, it makes up for in scientific value.

“It’s one of the world’s rarest fish – it’s found only in the Pilbara Coast and Barrow Island,” says Shane, who leads the team of 90 water experts in our Iron Ore business in the Pilbara, Western Australia.

“We discovered the eels were living in the aquifer near our Robe Valley iron ore mine, and so we needed to make sure that any future water activities, like dewatering, wouldn’t have an adverse effect on their habitat.”

As we dig deeper to get the iron ore used to make the steel found in everything from bridges to buildings, we often need to mine below the water table. To safely access the ore, as we dig down we need to remove the groundwater that would otherwise enter the pit. This is known as dewatering.

“Our job is to understand whether our dewatering activity could lead to a change in the groundwater level in local aquifers, and whether that would cause any adverse impacts on the aquifer, and on the animals and ecosystems that depend on it – like the blind cave eel,” Shane said.

Managing the impacts associated with dewatering and other water supply activities in the Pilbara are a long-term challenge for our business. To help us address this challenge, we have set a specific water target for our Pilbara iron ore business to complete six managed aquifer recharge investigations by 2023.

“Managed aquifer recharge” (MAR) is a process where we return water to aquifers in a controlled way, such as through boreholes or an infiltration gallery. A key part of our investigations is to determine the appropriate triggers that initiate operation of our MAR schemes. For example, if monitoring shows groundwater levels have declined to a pre-determined threshold or that dewatering in our mines has the potential to adversely impact environmental or culturally sensitive features, we identify this early and take steps to return water to the aquifer.

Over the last decade or so, MAR has come on a long way and is emerging as an important method for managing water resources responsibly in the mining industry.

“MAR is a pioneering and developing practice and its application in the Pilbara will be fundamental to improving our long-term environmental performance,” Shane says.

To be successful, MAR requires a thorough understanding of the hydrogeology in the region and finding a way to “recharge” the water in a way that suits the local environment and that gives proper consideration to our long-term water balance.

“Through our first two investigations, we have already learned a lot about how to design and engineer MAR systems.

“It’s all about being prepared, so if in the future, there is any indication our operations could adversely affect groundwater levels, we’ll be able to counteract that by returning water back to the aquifers.

“Closure is a real driver for our MAR investigations too.

“What we are learning now could be used longer term when we are closing mines,” Shane says.