A good understanding of mine water management issues related to underground and open pit mines depends on collecting a comprehensive hydrogeological data set. Data collection is the most time-consuming and costly stage since it requires gathering substantial amounts of long-term seasonal data. With this data available, a conceptual model can be constructed and subsequently converted into a 3-dimensional numerical model to simulate and evaluate the mine development.
Where possible, SRK recommends that clients use exploration and geotechnical boreholes for hydrogeological purposes; this approach has many advantages. Exploration holes can be used for hydrogeological and environmental data collection, producing large savings in cost and time. Besides these advantages, it is possible to save on operational costs and protect the environment.
Operational cost savings. Drilling exploration holes can have adverse effects on mine development because they can link different groundwater systems hydraulically. In open pit mines, slope stability can be affected if groundwater seeps into sensitive slopes, thereby reducing stable slope angles or necessitating dewatering costs. In underground mines, hydraulic connection can lead to inflows and higher pumping and treatment costs.
The solution is to develop a preliminary understanding of the groundwater system integrated with a good exploration drilling management plan to ensure that boreholes are properly sealed after data collection if these leakage risks are present.
Environmental protection. When investigating sites such as waste dumps, tailings facilities and leach pads, special care must be taken to avoid opening up pathways for contaminants through investigation and exploration holes.
In recent years, SRK Ankara used many exploration holes for hydrogeological data analysis. At one of the largest gold mine projects (Koza Gold) located in Western Turkey, geotechnical drills with depths ranging from 200-400m were used. Important features were tested using packer testing and holes were converted to piezometers to monitor phreatic levels or groundwater response during pumping tests. At the Kısladağ gold mine project, which will be the largest open pit mine in Turkey, a total of approximately 3000m exploration drills were utilised for hydro testing; a total of 100 packer test and airlift tests were conducted and holes were converted to piezometers for long term monitoring. For another feasibility study, the Yenipazar project, where a total of 1700m of exploration holes were converted to piezometers to monitor groundwater levels, the precise shape of the piezometric surface was modelled in a very early phase.
SRK advises mining clients to consider using all types of boreholes, particularly those developed in the early stages of a project for characterising the groundwater system. A properly structured and managed approach to borehole development can result in an efficient, environmentally-sound and cost-effective hydrogeological data collection program.
