Abandoned coal mines across the Donbas are filling with water, threatening drinking water quality on both sides of the separation line

, Veronika Melkozerova reports for NBC News from Toretsk, in government-controlled Donetsk. As water fills the mines, methane is pushed to the surface triggering explosions, she reports. Of the 121 working mines in the Donbas, 88 are in the Russia-controlled sector, says Ukraine’s Energy Ministry. Over the next 20 years, Ukraine intends to close most of its coalmines, partly with German and Polish aid. Ukrainian experts say the separatists have stopped pumping water from a dozen mines, including Yunkom site of a controlled nuclear detonation in 1979.