Megan Davies, North Carolina’s chief epidemiologist, resigned this week in the latest bit of drama over drinking water safety — drama that involves the state’s biggest utility and the administration of Republican Gov. Pat McCrory. Davies, who accused state officials of deliberately misleading residents, gives up her post of seven years and an $188,000 annual salary.

The story begins in 2014, when a Duke Energy power plant spilled 40,000 tons of toxic coal ash and 27 million gallons of wastewater into the Dan River. The ash is a byproduct of burning coal, and it’s harmful to people and ecosystems, containing silica, mercury, cadmium, and arsenic.

In the aftermath of the spill, public concern grew over Duke’s 32 coal ash storage sites around the state. Many of them were revealed to be unprotected, sitting in unlined basins — just heaps of coal ash in giant pits, leaching toxic elements and a carcinogen called hexavalent chromium into the water table.