Acid Rock Drainage (ARD), also known as Acid Mine Drainage (AMD), occurs when sulfide-bearing mine wastes like pyrite are exposed to oxidizing conditions in the presence of water. In the Thar region, the Thar coal deposit, a lignite-grade coal found in the oldest sedimentary formation (Bara – Eocene/Pliocene), poses significant environmental risks. Pyrite, the primary source of sulfur in coal, contributes to acid generation and spontaneous combustion. ARD in Thar Coal Mine (Block II) could result in acidic water contaminating the dune sand aquifer, which is the main source of domestic water in the region. This study evaluates the ARD potential of the Thar coal deposit and explores mitigation methods. Acid generation testing on samples from Bara, sub-recent, and dune sand formations revealed that coal and carbonaceous claystone from the Bara formation are potential acid-forming (PAF) and prone to ARD. Meanwhile, waste layers from dune sand and sub-recent formations are classified as non-acid-forming (NAF) rocks. Acid Neutralizing Capacity (ANC) tests showed that the dune sand and sand lenses from the sub-recent formation have moderate to strong acid-neutralizing capacity, which could be utilized to counteract acid generation by being strategically placed with PAF materials.
Keywords: Acid generation potential, Acid neutralization capacity, Bara formation, Potential acid forming rock
