Mining activities will eventually end, while one of the options for the use of post-mining land is to make it a pit lake. To ensure the management of the pit lake in the future, it requires a study about geochemistry of the water to be formed. Quality of the developing water is results in the reaction between water and rock on pit wall. This research was conducted with the aim of identifying quality of the water to be formed. To determine quality of the water, a direct test was conducted in the field using the pit wall leaching method. The location of this test was in PT Kaltim Prima Coal, one of the largest coal producers in Indonesia. There were three locations considered to represent rock stratification exposed on the pit wall. Dimensions in test was 1 x 1 meter, while leachate yield was 2 liters. Test cycle was conducted in daily, three-day, and weekly cycles. Based on the result of static tests, sample A was classified as NAF rock, while samples B and C were classified as PAF rock. Meanwhile, leachate test shows the result that range of pH values was from 7.61 to 8.02 for sample A, from 1.99 to 2.77 for sample B, and from 2.89 to 4.09 for sample C. Based on test result, the most dominant metals were SO4, Mg, and Fe. The conclusion of this research is that the exposed rock on pit wall is dominated by PAF rock, thus having a potency to form acid mine drainage.
Oleh :
Edy Jamal Tuheteru
