What causes clear, fresh country well water to turn orange or black, or smell so bad that it's undrinkable?
Some residents of a small western Pennsylvania community say it was nearby fracking for natural gas. Others say it's pollution from old coal mines. And experts say it could even be a baffling mix of natural and manmade reasons that change the water over time, like the leaves change on trees.
State officials and two federal agencies haven't found evidence that gas drilling caused the problems. But a Duquesne University team suspects that drilling may have indirectly impacted groundwater.
Local officials say they're trying to bring water lines to the area, but residents aren't sure they support that, either.