Mining of Minerals and Groundwater in India

Abhay Kumar Soni

### Abstract

Mining of minerals is essential for our day-to-day life so is the groundwater. Mother Earth is the custodian of these two essential commodities, and both are part and parcel of sustainable living for human beings. This chapter of book focuses on the need, quantity, quality, and management of groundwater encountered in mines, from where extraction of minerals takes place. By understanding interrelationship between groundwater hydrology and mining, the basic objective of sustainability, that is, conserving for future generations with particular reference to the mines, has been addressed. Such scientific approach makes the mine planning easier, ensures better water management, and solves water scarcity as well as security problems in the vicinity of mining areas.

Keywords: surface mining, underground mining, impact of mining on groundwater, quantitative estimation in a pit, statutory compliance, groundwater in hard rocks

### 1. Introduction

Minerals and their exploitation had been carried out since centuries by two major methods, namely, surface mining methods and underground mining methods. In both these methods, groundwater role is important as well as advocated because mining has influence on hydrology. While permitting mining, the disturbance to the hydrological regime should be minimum or as less as possible.

It is beyond doubt that for food security, human health, energy, and ecosystem, groundwater is absolutely important for the entire world [1].

This groundwater is continually being put under increasing stress because of the industrialization, growing needs of the population, and its improper use as a resource. Its mismanagement has led to uncalled water scarcity in present time and also threatened us with water pollution problems. Groundwater science and its accurate estimation for the mining areas are a bit cumbersome because the dynamics of groundwater keep on changing as excavation size is changed. Therefore, the role of groundwater in mining of minerals assumes special emphasis which is analyzed and discussed as a separate chapter in this book. This knowledge, though very exhaustive, will be certainly helpful for the mining areas and mega-sized mining/mineral sector in improving the quality of human life.

While dealing with water problems of mines, three keywords must always be remembered as they are extremely important, namely, mine water (MW), groundwater (GW), and surface water (SW). Our focus in this chapter has been kept on

mine water and its analysis with respect to the two principal methods of mining, that is, opencast mine and underground mine only. Besides these principal methods, other methods are not covered, though other novel methods and technologies of mining do exist, for example, solution method, mechanical method, aqueous extraction methods (hydraulic mining), etc.

The MW analysis automatically covers SW and GW, as mine water is either/or a combination of both for all mineral types (categorized as fuel minerals, that is, coal and lignite; metallic minerals, that is, iron ore, bauxite, etc.; nonmetallic minerals, that is, limestone, dolomite, etc.; and minor minerals, that is, sand, building materials, etc.) and their extraction from earth called "mining of minerals."

In this introductory paragraph, it is apt to highlight some basic points of groundwater to deal mining of minerals, scientifically. "Groundwater" in surface mines is found below the water table and covered by a layer of soil and/or rock. Groundwater is always present at below ground level and indirectly available at the mine pit as "base flow." It gets intercepted while excavating mineral(s) in open mines. Availability of groundwater in open-pit mines and underground mine workings has number of differing dimensions of basic hydrology influenced by sitespecific geology. Thus, it requires basic knowledge of water flow and water movement (Darcy's law). Groundwater of mining area occurs in aquifers which are of different categories, namely, unconfined aquifers, semi-confined aquifers, and confined aquifers. The groundwater is contained either in the rock pore spaces or rock fractures/cracks depending on the rock types. Compared to the surface water, it is generally considered to be less easily contaminated, but this does not infer that groundwater is safe from pollution perspective. The groundwater can become contaminated where polluted runoff seeps through the ground to the water table or flows down through fractures or cracks in bedrock (seepages). Wherever surface water bodies are fed from groundwater sources, water contamination may be present in both, though isolated by ground cover. In addition, groundwater often contains dissolved minerals as a result of prolonged contact with rocks containing minerals of different types and varieties which can alter its quality, for example, the presence of arsenic, nitrates, and fluoride [2–6] in aquifers has been reported, and this is an indication for this. The depth of the groundwater at which it is present in and around the mine area is a one major point of observation as well as concern for mine water-related issues.

To understand groundwater-related problems of mine, hydrological and geological setup of the area is first studied. With reference to any mine or the mining area, hydrogeological setup encompasses aquifer characteristics, that is, nature, type, parameters, etc.; all local and regional geological details; and plans for mining and total picture of hydrology, drainage, discharge, etc. The approach for scientific investigation, to search solution, usually includes field monitoring (pre-monsoon and post-monsoon monitoring), instrumental survey (e.g., Resistivity Image Profiling Survey and GPR Survey, etc.), groundwater modeling, and mine planning, that is, drainage, dewatering, etc. Mine being a production enterprise (unit) requires its assessment from industrial perspective; hence, this chapter makes no pretense of neither mining engineering nor of hydrology but explains to the reader the interrelation of mining process with water in general and groundwater in particular.

Here, it is equally important to describe briefly what new insights the work has added in terms of knowledge on top of the existing knowledge. In general, mining of minerals and groundwater pertains to the open-pit mining of minerals. Technical literature is also vogue in terms of analysis and with particular reference to the surface mines only. Very little had been dealt about different aspects of underground versus groundwater in mining science. But in this book chapter, both "underground mining" and "open-pit mining" knowledge have been dealt together

Mining of Minerals and Groundwater in India DOI: http://dx.doi.org/10.5772/intechopen.85309

forming a consolidated base and considering that groundwater is equally important for operative underground mines. Such attempt will provide total and at-a-place look to the reader. Not only this, but it will also enhance further scope of knowledge development, to be done by other researchers, in underground mines/mining and other excavations, which are less researched. Site-specific and typical field conditions will certainly add further to the existing groundwater knowledge base and make underground excavations further safe as well as productive.
