Coal Piles are non-constructible locations that contain Coal. Coal can be extracted from Coal Piles by assigning citizens to them directly or by constructing and manning Gathering Posts in their vicinity.
Additionally, Coal Thumpers can create and replenish Coal in Coal Piles. While Coal Piles start out with 500 Coal when the scenario starts, they can have a maximum of 1,500 Coal when replenished by a Coal Thumper.
Most scenarios start with 4-5 Coal Piles. The only scenario that does not start with natural Coal Piles is The Fall of Winterhome, however this scenario has two prebuilt Coal Thumpers to supply your city.