Coal ash is captured before it can escape at a smoke stack into the air, it's channeled into ponds near the river and contained there by earthen dikes.

NPR: In Tenn. Town, A Muddy Christmas For Some

El Mogote has an air of increasing permanence: a stack of new wood for building blocks the mud track entering the settlement.

ECONOMIST: Honduras

The blue-faced man lowered the piece of paper in his right hand onto the left-hand stack, transferred it instantly to the right-hand stack, then lifted it once again into the air.

NEWYORKER: Ziggurat