by Arash Roshdieh — Principal Engineer
Water is Balance
ATC Williams endeavours to provide leadership in sustainable Tailings, Water and Waste management solutions. Tailings, Water and Waste are engraved in our DNA, with Water as the glue that connects it all. We have found our fortieth anniversary to be a perfect time to reflect on both the journey and future perspective.
Our company founder Paul Williams has an infamous saying, “if you want to sort out your tailings problem, sort out your water problem, tailings will follow”. That explains why ATC Williams has always had a special interest in water management in mining activities.
We have always aimed to provide innovative and integrated water management solutions. From the early adoption of Walter Boughton’s 3 parameter yield estimation model in our early daily water balance utilising GW-Basic programing language to our recent and more sophisticated Monte Carlo analysis.
A Philosophy of Conservation and Protection
Our philosophy when considering water is: Any activity undertaken within the environment is somehow related to water. The activity could be a mining activity, a town, a waste dump, a production plant, etc.
Therefore, water is defined in relation to the environment, the activity and society.
In an integrated perspective, water is:
- Considered as a resource for the activity, or
- Must be managed around the activity.
In the former, our objective is water conservation. In the latter, it is environmental protection.
This perspective defines our values as follows:
- We have an integrated view to water solutions
- We create solutions that are both safe and cost-effective
- We mitigate adverse environmental impacts
- We strive for excellence with progressive thinking
On this basis, we trust that the combination of integration, unique culture, values and a set of exceptional skills will provide sustainable water solutions that result in success for our staff, clients, communities and environment.
Water Solutions – from philosophy to practise
Holistic Water Solutions
Our skills in providing Water Solutions are:
- Hydrology and Hydrogeology
- Hydraulic Structures and Engineering
- Water Resources Management
- Water Quality and Geochemistry
- Environmental Engineering
These WATER skills are utilised in conjunction with TAILINGS and WASTE skills to generate an integrated and holistic approach to our client’s problems. Key areas where our holistic water skills are applied in practise are outlined below.
Water and Tailings Management in Mining
The ATC Williams approach to mine water and tailings management is holistic, focusing on water conservation. We combine the latest dewatering technologies with safe tailings management plans to achieve the optimum water conservation objectives. A range of specialist laboratory tests enables us to understand tailings and water behaviour in more depth.
The typical tailings deposition schemes that are used, such as Paddock or Ring-Dyke impoundment, Valley impoundment either Down Valley discharge (DVD), Up Valley discharge (UVD) or Central thickened discharge (CTD), Dry stack (Filtered tailings), etc. are combined with the latest dewatering technologies, including various thickening and filtration technologies to provide the most efficient water recovery and tailings deposition solution.
We use sophisticated modelling techniques to generate climatic and environmental scenarios and combine them with different operational conditions. The outcomes are used for stochastic analysis of water management systems. This provides clients with a powerful tool to predict and reduce environmental risks.
Seepage Modeling at TSFs
Seepage management is crucial in reducing failure events which can have unintended consequences associated with water balance and social operating licence. Hydrogeological risks associated with seepage from Tailings Storage Facilities (TSFs) are connected to impacts on groundwater levels and reduction in environmental water quality.
Of concern is foundation failure which is the most common cause of TSF failure, and environmental and regulatory consequences due to potential migration of contaminants offsite. Seepage emanating from the TSF can migrate in both the vadose and saturated zone along preferential pathways. In general terms, two seepage pathways are present, one through the embankment and a second associated with seepage through the footprint area.
Representative conceptual models are relevant to site conditions and are essential to reduce risks associated with seepage and migration of contaminants in groundwater.
The groundwater-tailings interaction problem is a hydrogeological and geotechnical issue. Our approach provides an improved understanding of groundwater-tailings interactions underpinned by a conceptual framework, and analytical and numerical modelling, depending on the complexity of the aquifer system. An integrated team works together to provide appropriate hydrogeological design at all stages of the study.
Tailings Dam Break Analysis
Another area in which ATC Williams has developed a unique approach is dam break analysis for tailings embankments. A breach in the containing structure of a TSF can lead to catastrophic environmental, social and economic impacts and potentially result in loss of life.
Unlike a water dam break, the flow of the released tailings from a TSF is mainly dominated by the non-Newtonian behaviours of the tailings slurry, which is determined by the hyper-concentrated solids effect and rheological characteristics of the material. Modelling tailings flow as water (Newtonian flow) may lead to unrealistically larger inundation areas, shallower depth of flow and higher velocities, which may consequently result in an unrealistic consequence category assessment. At ATC Williams, we include the Rheological properties of tailings, measured at our Laboratory in Melbourne, in our tailings dam break analysis.
The estimation of tailings released volume is another crucially important factor for a tailings dam break analysis. Most of the methods currently used to estimate the tailings released volume are based on empirical correlations that do not consider important aspects such as dam raise type, deposited in-situ density, strength and liquefaction potential, and post-liquified residual strength.
At ATC Williams, we utilise our geotechnical expertise to estimate the quantity of the released tailings volume with a realistic approach that utilises the tailings post-liquefied shear strength ratio and the tailings in-situ density. Using this approach, our clients receive an accurate understanding of the risk and consequences of TSF breaches.
Creating a Legacy
The first forty years have been a long and exciting journey, and we cherish every moment. We strived to place integration, innovation and excellence at the forefront of our activities to the benefit of our clients. Looking ahead, it remains our mission to transfer these values from the first generation of water solution experts to the next.
Arash Roshdieh is a Principal Engineer in ATC Williams’ Melbourne office. Arash is a civil/water-tailings engineer, specialising in dry climate hydrology, tailings and water management and engineering.