I'm wondering if anyone has details on how stacking settlers/engineers/units with engineer abilities work on long term projects like building mines in mountain tiles? It has been my experience that settler turn labor and engineer labor stack pretty well, if not evenly and can drastically reduce the time of labor but not labor turns. IN other words, roads take two labor turns to build and you have engineers with a movement of 3, they move onto movement one grassland, one engineer will build a road on the grassland in one turn, whereas two engineers will be required to build a road on a movement two hill as 2X2 is 4 labor units. I think this applies to mining and irrigation. The stacking does NOT occur with engineers and units with engineer abilities (UWEA), but I think settler and UWEA stack just fine, 80% sure of that. Not tested with multiple kinds of UWEA, but I imagine they would all stack as the code for UWEA is all the same. I'm wondering how much this stacks though. Though this is is for scenarios, if you had a super duper terrain type that took 100 turns to irrigate, could you dogpile 50 settlers on it and irrigate it into a new type in 2 turns? And while I don't think this works with terraforming, if I'm wrong, please do tell.