AFŞİN-ELBİSTAN KÖMÜR ÜRETİM SAHASINDA OLASI DRENAJ SORUNLARININ HİDROKİMYASAL VE İZOTOPİK TEKNİKLERLE İNCELENMESİ
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The principal reason of the drainage problem encountered during the mining activities in Afsin-Elbistan Coal Basin, is the excess hydrostatic head of the karstic aquifer that extends beneath the coal zone. Afsin–Elbistan coal basin has a reserve of 4.5E09 tons of lignite approximately. A sustainable mining for coal production, groundwater inflow towards the open pit should be prevented effectively. There are two open pit coal mines (Kışlaköy ve Çöllolar), in which drainage activities have been carried out. In the Kışlaköy mine, the amount of annually drained groundwater from the karst and gyttja aquifers are 70E06 and 7E06 m3, respectively. In the Çöllolar mine the amount of groundwater drained in 2016 is 10.5E06 m3 and the same value of groundwater is drained today. According to the groundwater budget calculations, 837,40E06 m3/year of recharge and 868,25E06 m3/year of discharge is determined. The difference between these numbers is 30,85E06 m3/year and corresponds to the amount drained by wells. Despite extensive drainage in both mines, sufficient drawdown has not been achieved in the karst aquifer. The 50E06 tons of landslide that occurred in February, 2011, seems to be associated with the ineffective drainage of the karst aquifer. In different parts, the groundwater flows from northwest to southeast and from north to south of the pull-apart type coal basin. Water samples have been collected from 37 different locations representing the entire basin. All water samples belogs to Ca/HCO3+CO3. The isotopic composition of water samples indicates mixing of old and young waters. Hydrochemical evaluations suggest that the groundwaters, threatining the coal production originate mainly from the karstic akiquifer which is overlain by the coal layer. The groundwater system is recharged directly from the precipitation. There is no appreciable difference between the water samples representing wet and dry periods. High SO4 concentration observed in some of the water samples of karst aquifers seems to originate from the water contribution from coal layer. Different drainage techniques should be investigated due the low hydraulic conductivity of the gyttja aquitard. For a sustainable coal production, the groundwater head in karst aquifer should be lowered to a reasonable level table or the hydrostatic head to a reliable level, would solve many of the groundwater problems. Additional drainage wells should be drilled in the karst aquifer. Hurman Creek should be sealed particularly in the area where it enters the mining sector.