Conference Agenda

Mine Hydrogeology
Tuesday, 13/July/2021:
1:00pm - 3:05pm

Session Chair: Edward Austin
Location: Meeting Room 3

1:00pm - 1:25pm

Investigating Subvertical Dewatering Well Potential At An Open Pit Mine

Patrick Moran, Joe Ross, Ramsey Way, Rod Williams

Iron Ore Company Of Canada (IOC) / Rio Tinto, Canada

Groundwater is an operational risk at the Iron Ore Company of Canada (IOC). Orebodies being mined are currently dewatered via borefields comprised of vertical wells. While vertical wells are a proven technology, and have enabled mining to progress below water table, they are not an optimal solution. Subvertical wells are an optimal alternative. Two subvertical pilot holes were recently drilled at IOC. Both intersected favourable geological, geotechnical, and hydrogeological characteristics and are therefore interpreted as viable well targets. This paper presents investigative drilling results, in the context of well theory, and advocates for the construction of subvertical wells at IOC.

1:25pm - 1:50pm

Slope Depressurisation at Sishen Mine, Northern Cape, South Africa

Travis Hamilton White, Marnus Bester, Richard Carey

Anglo American Kumba Iron Ore, South Africa

Prior to 2014, the dewatering program at Sishen Mine focused exclusively on the deep fractured aquifer and neglected the upper shallow aquifer. In November 2014, increased pore pressures in the shallow aquifer led to slope instability with subsequent slope remediation measures costing more than USD9 million. This initiated the development of an active depressurisation program in its largest pit (GR80), to alleviate pore pressures. The system is an excellent example of the value of an effective depressurisation system which enabled slope design optimisation unlocking substantial value through a 24 million ton reduction in waste stripping and reduced production delays.

1:50pm - 2:15pm

The Use of Mineral Exploration Drilling to Kickstart Hydrogeology Data Collection for Pre-Feasibility Mining Studies and Beyond.

Kym Lesley Morton

KLM Consulting Services, South Africa

Groundwater information can be collected very inexpensively during exploration drilling, with holes used to create an early monitoring network. Information on water intersections, circulation losses, water chemistry and rest water levels can be collected by the contractor and site geologist.

Collection of basic information significantly reduces the cost of the initial hydrogeological study for the pre -feasibility reports. Decision criteria are provided for the use of the hole after drilling to optimise information and reduce risk when mining commences.

2:15pm - 2:40pm

Application Of Detailed Interval Flow Data Measured In Drillholes With PFL Tool In Hydrogeological Conceptualization And Numerical Flow Modelling For Mine Feasibility Scoping

Elias Pentti, Eero Heikkinen, Tiina Vaittinen

AFRY Finland Oy, Finland

Hydraulic drillhole measurements with the Posiva Flow Logging method have been performed at a planned open pit mining site in Northern Finland to acquire input data for numerical groundwater modelling. The high spatial resolution and low detection limit of the method enabled determining the hydraulic conductivity of bedrock, its depth dependence, and differences between two pit locations on a level sufficient for the numerical modelling. Separate FEFLOW models for two planned open pits were compiled and used to calculate groundwater inflow into the pits and effects on the water table in projected mining phases.

2:40pm - 3:05pm

Spatial and Temporal Changes of Physico-Chemistry Aspects of Mine Water, Due to Post-Closure Water Management

Lee M Wyatt, Jack Cropper, Ian A Watson

Coal Authority, United Kingdom

This paper describes how data collected from shaft sampling and electrical conductivity logging has been used to aid the assessment of complex mine systems. The paper focuses on sets of data from 4 coal mine shafts in the northeast of England, where sampling and logs have been undertaken from 2000 to 2020. The sites show both mine water level rise and ongoing mine water pumping to control the water level and prevent pollution. The paper shows how the mine water has changed over time, and also how pumping has influenced the water stratification in the shafts.