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WATER MANAGEMENT 42 E&MJ; • JANUARY 2017 www.e-mj.com Water management represents a signifi- cant area for cost control for mining oper- ations. A properly engineered network will cost less to build, operate and maintain, lowering capital expenses (capex) and op - erating expenses (opex). Moreover, ensur- ing all water management activities are completed in timely fashion, they should not affect the mine plan or mining oper- ations, avoiding additional costs to the business. Take the new $A10 billion Roy Hill iron project in the Pilbara region of Western Australia as an example. It will produce 55 million metric tons per year (mt/y) of iron ore from multiple surface pits and production benches. Before min - ing operations can begin, the site water table must be lowered to provide dry digging conditions. The mine will also require water to process ore. The mine's water system will consist of an evolving, integrated network of water supply and dewatering operations extending across most of the 300 km 2 mining lease. Within the water supply scope there are various consumer facilities with differing feed requirements in terms of both wa- ter quality and quantity. Up to 22 mega- liters per day (ML/d) of high-quality water will be required for final ore processing and potable water (after treatment) pur- poses. This is supplied by 24 dedicated supply bores from the Stage 1 borefield. A further 34 ML/d of lower quality water will be required for ore processing make- up and dust suppression supplies. This is currently delivered by eight separate construction water supply bores and the greater, progressively expanding dewater- ing network. Over the 20-year life of the mine, there will be two distinct dewatering systems, raw and saline. Currently on site, there are approximately 48 active raw dewater- ing bores. The raw dewatering system is estimated to peak at 105 active bores in 2023. As mining operations deepen and progress southwest, the dewatering sys- tem will turn progressively more saline; requiring the separate network. Saline dewatering operations are not expected to begin until 2018, with a peak of 75 bores expected in 2021. During peak operations, around 213 bores (138 raw and 75 saline) will pump approximately 140 ML/d through a net- work of 220 km of high density polyeth- ylene (HDPE) pipework ranging in diam- eter up to DN800. These peak quantities will be maintained as dewatering bore- fields are progressively installed and re- moved as mining operations migrate. Engineering the Network Roy Hill's Water Management Team, as part of Operations Engineering Services, is responsible for all facets of site raw water supply and dewatering, such as planning, design, construction and opera- tions. This includes but is not limited to: • Ensuring adequate supplies to the vari- ous locations; • Providing water of acceptable quality to the desired locations; • Preserving limited good quality ground- water supplies; • Supplying water to new mining locations; • Maintaining the ground water level a minimum 1 m below the base of active mining operations; • Ongoing expansion of dewatering opera- tions sufficiently ahead of mining; • Spatial fit of the water infrastructure within the operational footprint to mini- mize conflict; and • Disposing of excess dewatering by ac- ceptable methods during periods of water surplus. They are achieving this using Water- GEMS software, a mapped, fully integrat- ed hydraulic model. The model allows a detailed representation of the water system providing a full understanding of the dynamic nature of the network; both through system expansion and changing yield and quality characteristics of the bores over time (Immature -> Intermedi- ate -> Mature). Water management at Roy Hill has a to- tal sustaining capital budget on the order of A$440 million over the course of the mine's life. The Water Management team is currently looking at ways to optimize the design of future systems to reduce the potential size/rating of infrastructure and its overall cost. For example, a pipe with Water Management Models Save Time and Money Using the software to create multiple design options, engineers actively manage Roy Hill's dewatering program Modeling the hydraulic network allowed the Roy Hill water management team to cost effectively balance dewatering needs with operational consumption.