Improving deep-level mine water usage through dynamic baselines and accountability methods

Abstract

South African gold mines are extremely complex and dynamic operations in terms of several factors such as logistics, depth of mining, infrastructure and variable geological conditions. These operations progress deeper, well below 4 000 m, searching for new gold-bearing ore reserves. As mines progress deeper, additional cooling and ventilation requirements are needed to combat the high virgin rock temperatures. This results in bigger and more complex water reticulation systems that provide cooling and services to underground end users.

Gold production is decreasing while operational costs continue to increase, reducing the profitability and sustainability of mining operations. External factors such as rising electricity tariffs, declining gold grade, and unstable gold prices contribute to this trend, but remain beyond the mine's control. Inefficient operations, particularly water losses from leaks and misuse or malpractice, which account for up to 50% of underground water use, present a key opportunity for intervention. To decrease operational costs, focus must be placed on identifying and addressing water inefficiencies.

Water leaks tend to occur closer to the working areas as this is where personnel spend most of their time. However, current methods used to localise water leaks in working areas are time and resource intensive. Furthermore, these methods fail to continuously identify water leaks in the working areas as they occur due to their static and infrequent nature. Zero-waste baselines (ZWBs) were highlighted as the best method for wastage identification. Still, limitations in current approaches include static and broad applications. These are typically implemented only up to half levels and rely on fixed timetables and best operating points for equipment.

Identification alone will not solve the problem and leak mitigation is often overlooked where focus is placed on supply-side initiatives such as water isolation and pressure management. These measures are only effective during non-operational times. Furthermore, large leaks are only attended to when normal production is disrupted, making them part of everyday operations, which neglects smaller leaks. Furthermore, no reliable system is in place to confirm whether leaks have been fixed. Employees also rarely fix and report leaks themselves as the operation's focus lies with production and roles regarding leak fixing remain unclear.

To address the problem, the study introduces an accountability framework that applies dynamic ZWBs to identify and mitigate water leaks within operational working areas. The framework incorporates core accountability components to improve performance and drive sustainable operational improvements. The development of dynamic ZWBs will enable faster and more accurate detection of inefficiencies within working areas. Additional metering is installed in working areas with a life of mine over one year to measure the actual water consumption, compare it to the ZWB and identify wastage. Using accountability will ensure that water leaks are not only identified but mitigated to reduce operational costs.

The developed method was implemented on a South African gold mining operation, referred to as Mine A. ZWBs were developed for each working area, which reduced the identification period significantly when compared to current methods. The ZWBs were used as performance measures where a responsible person was assigned to each working area to ensure that identified leaks were mitigated. A monthly cost saving of R235 000 was obtained for the case study working area, resulting in a payback period of 9 days for the installed equipment. This equates to an annual cost-benefit of approximately R28.7 million for Mine A. The results obtained validate the effectiveness of the developed method. All objectives of the study have been met by the evaluation and the validation thereof.