Pilbara Water World

While the Pilbara region has a reputation for its dry climate, there is no shortage of below-ground water in the nation’s iron ore heartland – a factor the majority of sector operators grapple with on a daily basis as they move further beneath the water table.

One organisation leading the way on water management systems in the region is relatively new entrant Roy Hill, at its much-publicised $10 billion, 55 million tonne per annum namesake iron ore project.

For Roy Hill, the maintenance of a one-metre barrier between the pit floor and water table was a stipulated requirement prior to project funding was granted.

A budget of $60 million was set aside for the establishment of an effective and adaptable water management system at the mine – an integrated network of water supply and
dewatering operations which extends across most the of the mining tenement, covering some 300 square kilometres.

And while public focus may sit on the headline figures of production tonnage and production cost, the water management system at Roy Hill is a vital, efficient component in achieving both – and any mining at all.

“After the composition of geology of the ore body, water management is the next most important area for any mining operation,” Roy Hill Engineering Services Water Planning Engineer Craig Nelson told National Mining Chronicle.

“If you don’t get dewatering right, you can’t mine,” he said.

They certainly got it right at Roy Hill if initial production – and the results of the 2016 Bentley Systems Be Inspired Awards, where the project took out the Innovation in Water Network Analysis category – are anything to go by.

Roy Hill’s extensive water supply and dewatering network was one of two Australian recipients of a Be Inspired Award, which offers global recognition for the world’s most outstanding advancements in infrastructure design, construction and operations.

With costs a particular focus for iron ore producers in a volatile commodity price environment, the water management team at Roy Hill received plaudits for carefully modelling and designing the mine’s water system to be efficient and cost effective.

The model and design was carried out in partnership with Bentley Systems using WaterGEMS hydraulic models – a system which allows the team to model current and future scenarios, enabling optimal pipe size and pressure ratings.

“Roy Hill optimised pipe sizes and pressure rating in the design process using WaterGEMS hydraulic models,” Mr Nelson said.

“By doing this and reducing the pipe size by one of Roy Hill’s preferred standard dimensions or pressure rating, it can save as much a 33 per cent in material costs.

“Roy Hill also utilised fit for purpose, cost-effective designs and strategies – we removed the ‘bells and whistles’ where they were not required.

“Most recently we have begun using variable speed gensets to reduce fuel consumption on bores at yield drops.”

WaterGEMS is also used to optimise the running order of supply bores to lower running hours and fuel consumption.

Modelling through WaterGEMS allowed the Roy Hill water management team to more quickly understand the implications of its decisions, and avoid delays to mining operations and risks to the dewatering network.

Based on the modelling, significant cost savings are expected across the 20-year initial life of the project, including $16 million by better modelling and designing the system’s operating pressure; $10 million in reduced equipment costs; $1 million in redesigns and alterations; and $20 million in operational expenditure and a further 20 per cent in operating run hours and fuel use.

Mr Nelson said the company hoped to use WaterGEMS for further applications moving forward.

“Looking to the future we would hope to monitor?water quality changes to ensure we are meeting supply obligations and defer treatment and disposal requirements as long as possible,” he said.

While the water management system at Roy Hill is currently up and running, there is plenty of room and requirement to expand as the company takes the project forward; the system will be adapted to meet transitioning requirements over its life.

“By any measure the scale and complexity of the Roy Hill project is at the large end of the spectrum,” Mr Nelson said.

“There are currently 79 bores and around 56km of pipelines – our estimated peak is 213 bores which would see us expand to approximately 220km of pipelines.

“The Roy Hill minesite is currently providing up to 60 million litres of water per day. Dewatering is required to operate 24/7 to achieve drawdown targets, while supply bore priorities are changed to ensure the system runs evenly and efficiently.”

Part of the challenge for the system is the handling of both raw and saline water. Each are to be managed by a separate set of bores – 138 raw and 75 saline at the estimated peak of 213 – with the dewatering system turning more saline the deeper and further southwest the project develops. Saline dewatering isn’t expected to begin until 2018.

As is evident from its award-winning water management system, Roy Hill has learned plenty in the space from other operators in the region and around the globe.

However, Mr Nelson said the company’s philosophy in water management would be to continue to expand on the lessons learned and strive to deliver the best possible result for the project.

“Roy Hill as an organisation is constantly seeking to improve on the status quo and innovate where possible,” he said.

“At the mine, we manage fresh and saline water separately as the water quality feed to the process plant is important for the final product quality.

“We are currently trialling in-ground methods to reduce aquifer permeability and the amount of water needed to be abstracted.

“We are also taking a unique utilities approach to hydraulic modelling, rather than the ‘normal’ mining approach.”

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