In Kerala, over 90 percent of operational quarries are
dedicated to granite mining, highlighting its significance in this part of the
country. However, challenges arise due to Kerala's dense population and limited
available land for mining, with forests, landslide-prone areas, and assigned
lands posing constraints. The state's topography, characterized by slopes,
further complicates finding suitable mining sites, as flat land is scarce.
Community resistance is a common occurrence, as residents
oppose having quarries near their homes. Therefore, mining operations are under
strict vigilance, with public scrutiny ensuring adherence to approved mining
plans and rules. Any deviation from these plans can lead to the suspension of
quarry operations. Quarry owners must follow mining plans prepared in
accordance with the Metalliferous Mines Regulations of 1961 and the Kerala
Minor Mineral Concession Rules of 2015.
The mineral rights are vested in the Government. The
Department of Mining and Geology grants permissions for mining of minor
minerals (such permissions are known as mineral concessions) in Kerala, in line
with the Kerala Minor Mineral Concession Rules, 2015. According to these rules,
before granting mineral concessions, the applicant must receive a letter of
intent. Upon receiving the letter of intent, the applicant must submit a mining
plan prepared by a recognized qualified person (RQP) and also shall obtain
other statutory licenses. The letter of intent is granted by the Director of
Mining and Geology based on a field inspection report and Form II submitted by
the district geologists. For preparation of Form II, the geologist has to
assess the mineable quantity of mineral available and has to assess lease
period in years. However, there is a challenge in computing mineable reserves
accurately, as geologists sometimes miscalculate the recommended mining period.
The tendency to use a general rule of thumb, such as 3,20,000 MT of granite per
hectare, may result in inaccurate estimates.
This paper aims to explore the intricacies of mining of
granite (building stones) in Kerala, providing insights for stakeholders on
selecting suitable locations for mining operations while considering mineable
reserves. The goal is to educate quarry owners and other stakeholders,
including officials involved in granting mineral concessions, to make informed
decisions for sustainable and efficient mining practices in Kerala.
As per the current regulations and rules, there are three
essential requirements for conducting mining operations: 1) mining must take
place in benches, typically with a permitted bench height and width of 6 m (but
RQPs tend to submit mining plans with 5 m height and width) 2) mining should commence after maintaining a
7.5 m distance from the mine boundary, and 3) mining has to progress from top
to bottom (bench mining is feasible only when conducted from the highest
elevated area to the lowest lying area). In the context of a mining plan, the
geological reserve in a designated mining area encompasses the combined total
of mineable mineral reserve and the mineral reserve blocked in benches and
non-mining zone.
In Kerala, identifying barren rocky terrain is challenging, and in most cases, there is a substantial layer of soil, varying in thickness up to 10 m. Due to the high cost associated with managing overburden, miners prefer terrains with a soil cover ranging from 1 to 3 m. It may be noted that the only mineral exploration work required for granite mining is the estimation of overburden thickness.
In the preparation of mining plans for granite (building
stones), the mineral reserve is categorized into geological reserve, mineral
blocked in benches and non-mining zones, and mineable reserve. The geological
reserve comprises the total of mineable reserve and blocked reserve.
Since the mineral rights are vested in the government, a
quarrying lease must be obtained by the miner from the government. Both the government
(lessor) and the mine owner (lessee) primarily focus on the mineable reserve in
the applied land, as the determination of royalty is based on this reserve. For
the lessee, assessing revenue is also contingent on the mineable reserve.
Before 2015, mine owners
in Kerala practiced high wall mining for extracting granite building stone from
quarries. Although mining of granite building stone fell under the purview of
Metalliferous Mines Regulations, the mining operations typically resembled
box-type mining, as depicted in Figure 1. During this period, environmental
clearance was not required for mining areas less than 5 hectares, and there was
minimal consideration for blocked reserves with this mining method.
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| Fig. 1 Mining method adopted prior to enactment of Kerala Minor Mineral Concession Rules 2015 |
However, in 2012, the Hon'ble Supreme Court of India, in the
case of Deepak Kumar vs. State of Haryana, mandated environmental clearance for
mining minerals, regardless of the size of the mining area. In this judgment, all states were instructed to adhere
to guidelines issued by the Indian Bureau of Mines for mining minor minerals.
Consequently, the Government of Kerala enacted the Kerala Minor Mineral
Concession Rules 2015, replacing the Kerala Minor Mineral Concession Rules
1967.
Under the new rules, mining guidelines were made more
stringent, and a separate chapter was introduced for Mining Plans. As a result
of the updated regulations outlined in the Kerala Minor Mineral Concession
Rules 2015, mine owners in Kerala were compelled to cease high wall mining
practices and transition to benched mining methods.
Topographic Influence on Mineable Mineral Reserves:
When bench mining is practiced, the depth of the quarry is
restricted to less than half of the width of the quarry. The topographic
influence on mineable mineral reserves is depicted in the following diagrams.
All such quarries have almost the same area. These scenarios occur in Kerala,
although the numbers vary.
Scenario 1: Mining in Low to Medium Sloping Land
Most of the quarries in Kerala fall into this category.
Given Kerala's undulating topography, the likelihood of finding such locations
is higher. The mineable reserves in these quarries are sufficient to run the
quarry profitably.
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| Fig. 2. Slope mining in low to medium sloping areas |
Scenario 2: Mining in Steeply Sloping Land
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| Fig. 3. Mining in steeply sloping land |
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| Fig. 4 Mining in steeply sloping land with concave slopes |
Scenario 4: Mining a Mound – Top Slicing Method
If the quarry encompasses a mound, then it is possible to
conduct top slicing of the mound. The mineable reserves in such quarries will
be very high compared to quarries located on slopes or plain land. However, in
Kerala, such situations rarely occur as the mining area in most quarries is
less than 10 hectares. To encompass a mound in a quarry, the quarrying area
should be very large.
 |
| Fig. 5 Mining a mound -top slicing method |
Scenario 5: Mining in Flat Land
Mining in flat land yields a good mineable reserve compared to mining in sloping areas, provided the area is the same. However, there are no plain lands available in Kerala's midlands and highlands. Wherever plain land is available (for example, in lowlands), the thickness of the soil/overburden will be very high. It may be noted that maximum mineable reserve for a given area which does not involve mound mining, is limited to the mineable mineral reserve in a flat terrain. For example, for a given area and shape, the mineable reserve in a slopping area will always be less than the mineable reserve in plane land.
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| Figure 6. Mining in flat land |
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Conclusion
When selecting land suitable for mining, it is crucial to
consider the topographic features, particularly when dealing with limited land
area. Ideally, a mound presents the most favorable scenario for mining, given
that the shape of the mine remains constant. The next preferable option would
be flat land. However, acquiring suitable flat land for mining can be
challenging. In such cases, a sloping land with a moderate incline becomes a
viable alternative. It is advisable to avoid steeply sloping areas, especially
when the slopes exhibit a concave shape.
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