The excavation part felt unsatisfying. It was possible to build excavation rigs anywhere, but they weren't actually needed anywhere but Lakebed zones. This means that in most places, they just instantly finished... as opposed to in the places where they were actually needed, in which they finish almost immediately, making it seem hardly necessary. I'd suggest that the excavation process ought to take longer than a minute, as opposed to several seconds, to make the process feel more significant instead of just a checkbox.