I deliberately avoided trying to calculate an exact strip ratio...

I deliberately avoided trying to calculate an exact strip ratio for the same reason, plus I'm not a mining engineer so it's not my area of expertise.

I am talking more in general terms. With lignites like we have here a good deposit has a less than 1:1 ratio of overburden to coal. For instance Hazelwood mine in Victoria has a 150m coal seam only about 20m below the surface.

Here at NDH05 we've got 37m of coal 220m below the surface. I don't know what sort of geometry pit they are going to need but for such low value coal, I think you'd be pushing it to claim it's economic.

But who really cares? Up at their trench they've got coal almost at surface, which is where you need it to be if you're going to mine lignite.