Issues with open cast mines

What is the issue?

Open cast mines in Jharkhand continues to be a death trap.

What are open cast mines?

• Open-pit mining, also known as opencast mining, is a surface mining technique that extracts minerals from an open pit in the ground.
• It is the most common method used throughout the world for mineral mining and does not require extractive methods or tunnels.
• Generally a traditional ‘cone-shaped’ excavation is done.
• The technique is used when mineral or ore deposits are found relatively close to the surface of the earth.
• Open-pits are sometimes called ‘quarries’ when they produce building materials and dimension stone.
• Dhanbad has 105 mining leases altogether comprising underground, open cast and exhausted mining areas.
• Some leases are not operational because of lack of statutory clearances.

How the mining is done?

• Opencast mining operations involve the removal of huge quantities of overburden, dumping, and backfilling of the excavated area
• Overburden removal refers to the removal of top-soil to expose the coal seams making them ready for mining.
• Tailings are a by-product of mining. After ore is processed the resultant waste stream is termed “tailings”.
• Backfill typically contains these tailings.

What are the advantages of Open cast mining?

• Full visualization of exposed orebody and negligible ore loss
• Greater concentration of operations, better grade control and blending,
• No need of artificial light with natural ventilation round the clock.
• Greater safety, minimum mining hazards like gasification, roof and wall support.
• Easy pumping of sub surface water
• No restriction of working with heavy and bulky machineries.
• Lower capital and operating costs,
• Minimum mine development work
• Early production and quick return of capital invested.

What are the impacts of such mining?

• Ecosystem Damage - The ecosystem that was present at the time prior to mining activity is basically destroyed.
• Soil degradation – Various mining activities, particularly open pit, affect the topsoil and subsoil to a great extent by changing the natural soil characteristics. e.g. texture, grain size, moisture, pH, organic matter, nutrients etc.
• Overburden differs substantially from previous local soils, and some maybe even toxic for plants.
• Loss of agricultural and forestland - In case of open cast mining there will be complete loss of agricultural land and deforestation in and around the pit.
• Water pollution - Water pumped into mines can affect local water table depths, resulting in the release of acidic mining water into surface waters.
• The damage of natural drains and waste dumps may act as a barrier to the natural flow of rainwater
• Water logging and Flash Flood - This will result in water logging and flash floods which will damage the agriculture and to local properties downstream.
• The seasonal filling of nearby reservoirs and recharging of the groundwater around the area will be affected.
• Landslides - Opencast mining on hill slopes, particularly in areas of heavy rainfall, is vulnerable to landslides causing loss of human life, property and deforestation.
• This can be controlled by geo-technically designed slope of the mine and adequate support system.
• Affects livelihood - The land owners, often tribal population, and contractual farmers living within the Mining Lease area are affected.

How to overcome these issues?

• Loss of Agriculture - New agricultural land is developed and aforestation is done under overall land-use planning.
• Soil degradation - Topsoil and subsoil must be removed separately and stockpiled at an easily accessible place.
• These soils can selectively be re-laid to reclaim degraded land for agriculture
• Water logging and Flash Flood - The changes in the drainage pattern can be anticipated from the expected post-mining surface contours.
• Action plan for the surface drainage pattern can be designed accordingly.
• Landslides - This can be controlled by geo-technically designed slope of the mine and adequate support system.
• Rehabilitated people must be compensated by cash, separate housing, employment, health care, education, and other facilities.

 Reference

1. https://indianexpress.com/article/explained/jharkhand-open-cast-mines-death-trap-7753272/
2. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/opencast-mining