I'll add in addition to my post that the water could be a...

I'll add in addition to my post that the water could be a hurdle, but I'm sure the historical miners overcame that hurdle when they started the mine.

like Chopsthecat said, they could have seen the flooded bit to help combat ice. Remember ice expands when cold and could undermine structural integrity, or just be a pain in the arse.

also remember it's a Fjord, there's both fresh and sea water, the pit may be all fresh water from metled ice

And finally remember there's a whole lot of other tenement, that pit wasn't touched since 1963, yet they still exported all the cryolite from the tailings until the 80s