Where did the spoil pile go?

Short version: we removed it on purpose.

In the base game, dumping creates a pile — an object with an upper limit. With us, dumped material becomes real terrain instead, with no pile limit. That is the whole point: a heap you can dig out again, drive over and reshape.

If material spreads flat instead of piling up

There is a switch for that. freeDumpHeight (since 1.4.3.0, default on) lifts TerraFarm's 0.5 m check. Dumped from a height, material can then spread wide — which looks like "no heap".

Counter-test: set it to false in miningLayers.xml and dump close to the ground. The switch exists exactly as that escape hatch.

If the material cannot be picked up again at all, that is something else — please post here with map and mod version. That would be a case for the heap memory, and we will look at it.

One more note: the heap memory is tied to the savegame. A fresh savegame starts empty — that is normal and fills up again.