re COAL STORAGE
It really depends on your rainfall patterns.
As long as you don't have long periods of heavy rain in your location, and the moisture content of the coal is not a limiting factor, well-drained outside storage should not be a problem. Although you may need to occasionally cover the stockpiles with plastic tarpaulins in very heavy rain events.
In dry, windy weather, there could also be an issue with dust blowing off the stockpiles.