Research on the distribution pattern of the potential forming of acid mine drainage
(AMD), has been conducted on one of the coal mines of Loajanan block in
Samarinda, East Kalimantan, which is administratively not far from the city of
Samarinda and is traversed by the Mahakam River. AMD problems need special
attention in the world of mining before, while or after the mine ceased operations.
Loajanan block is one of the main block in the coal mine with an area of IUP
11648.715 Ha, which have sub blocks Simpang Pasir, Tegal Anyar, Purwajaya,
South Purwajaya, North Tani Bakti, South Tani Bakti and Sambutan.
Making the distribution pattern of potential acid rocks forming / non acid
forming (PAF / NAF) and the distribution of water pollution is computerized by using
Software Surfer. In this case, the distribution of rocks PAF / NAF in Loajanan block
was made based on parameters of geochemical characteristics of the rocks that is
total sulfur (TS), Pasta pH, net acid generating pH (NAG pH), NAG pH = 4.5, NAG
pH = 7, maximum potential acidity (MPA), acid neutralizing capacity (ANC), net acid
production potential (NAPP). Rocks in the west, northeast and south in the Loajanan
block included in the PAF type of low capacity (class II) with an area of 2085.783 Ha
and in the northeast also has rocks PAF type of high capacity (class IV) with an area
of 1682.247 Ha. While the rocks which belong to the type of NAF (class I) are in the
south and east in the Loajanan block with an area of 7880.679 Ha. So in general
(70.6%) of rocks on the Loajanan block not potentially acid forming (NAF).
Next is the distribution of water pollution in Loajanan block are made based
on the water quality parameters namely pH value, assays of Fe, Mn and TSS. Water
conditions in the eastern of Loajanan block has been polluted because it has a low
pH, contain heavy metals, total suspended solids and may be indicated to form AMD
that area is 9011.314 Ha. As with the water conditions in the western of the
Loajanan block which do not have the pollution, the area is 2637.395 Ha. So in
general (66.6%) of water on Loajanan block in polluted conditions.
There is a correlation between the distribution of rocks PAF with the
distribution of water pollution in the west, northeast and south in Loajanan block.
Similarly, distribution of rocks NAF with the distribution of water pollution in the west
and south in Loajanan block that have a correlation each other. Meanwhile, in the
south and east in Loajanan block not found a correlation between the distribution of
rocks NAF with the distribution of water pollution.
Pola penyebaran batuan potential acid forming / non acid forming (PAF / NAF) dan penyebaran pencemaran air dilakukan secara komputerisasi dengan menggunakan Software Surfer. Dalam hal ini, sebaran batuan PAF / NAF pada blok Loajanan dibuat berdasarkan parameter karakteristik geokimia batuannya. Batuan di daerah barat, timur laut dan selatan di blok Loajanan termasuk ke dalam tipe PAF kapasitas rendah (golongan II) dengan luas 2.085,783 Ha dan di daerah timur laut juga terdapat batuan tipe PAF kapasitas tinggi (golongan IV) dengan luas 1.682,247 Ha. Sedangkan batuan yang termasuk ke dalam tipe NAF (golongan I) berada di daerah selatan dan timur di blok Loajanan dengan luas 7.880,679 Ha. Sehingga 70,6 % batuan pada blok Loajanan tidak berpotensi membentuk asam. Selanjutnya ialah sebaran pencemaran air pada blok Loajanan yang dibuat berdasarkan parameter kualitas airnya. Kondisi air di daerah timur blok Loajanan telah tercemar karena memiliki pH rendah, mengandung logam berat, padatan tersuspensi dan dapat diindikasikan membentuk AAT yang luas daerahnya ialah 9.011,314 Ha. Lain halnya dengan kondisi air di daerah barat blok Loajanan yang tidak mengalami pencemaran, yang luas daerahnya ialah 2.637,395 Ha. Sehingga 66,6 % air di blok Loajanan dalam kondisi tercemar. Terdapat korelasi antara sebaran batuan PAF dengan sebaran pencemaran air di daerah barat, timur laut dan selatan blok Loajanan. Sama halnya sebaran batuan NAF dengan sebaran pencemaran air di daerah barat dan selatan blok Loajanan yang memiliki korelasi satu sama lainnya. Sedangkan, di daerah selatan dan timur blok Loajanan tidak ditemukan adanya korelasi antara sebaran batuan NAF dengan sebaran pencemaran air.