I'll see if I can be another one to add my thoughts of where the water comes from, and how EPM can mine the pit
From the overview of the tenement, we can see that the pit represents a mini cue amount of the tenement. Note that the brown hill is reasonably flat with lots of ice on it (especially in the winter) form the satellite view there does appear to have small creeks running from the the brown hill out to the water.
Let's zoom in to the pit in question we can see there are 3 other 'puddles' of water
located here and
Streams here
Not too sure how deep either one is, and appears the labeled source of water would be a reliable source of fresh water considering there is a network of creeks flowing straight to it.
we can see from this view the depression. though it appears on google earth (which I suggest you all have a play from here (https://earth.google.com/web/@61.2046522,-48.1710647,31.87961189a,0d,59.25000983y,149.17421285h,85.75497629t,0r/data=IjAKLEFGMVFpcE1TdWhjTWFSbDEtRWgyUFl3ZGZMRmZ0TXV3T3VTZWpIYlRCbFpXEAU) hit the yellow man when you want the satellite view.
Now none of us can tell from an Australian website where the assumption will be we are located in Australia, the source of water in the pit but it does appear to be fresh water from the colour of the water in this picture. Keep in mine that the pit water has had ice form on it.
here's a sea level photo of the sea wall 
make some comments on this, seems that the concrete was laid to ensure the road is flat and to also keep the sea out.
from the pit's cross section diagram we can see how thick the walls are between the pit and the ocean.
Finally I'd like invite people to have a guess as to when the pit was flooded. and to Find the last photo of the pit being dry, I'll post it later on (being the latest one I can find) though remember, the old miners didn't really dig and use the pit after 1960s, in the 70s and 80s they mainly continued to export Cryolite from the tailings. the pit is probably full of water from the sea, since it is on par with sea level, this suggests the pit is filled with sea water, keeping in mind it is in a fjord and could be fresh water, we know that salt water freezes at a much lower level, yet ice has formed on the pit.
My thoughts the water is fresh waterFor the concerns of contamination like nro brought up with Thorium. Th is slowing attacked by water. Check out the Environmental effects of thorium in this link as well as the facts on Th.
https://www.lenntech.com/periodic/elements/th.htmAs far as water being treated, there are some pits of water, I'd say my second red circle (the left one) could be used to temporary hold waste water from the pit, treated and then piped back to the ocean. NRO that question is way to loaded for anyone here to answer.
You're also assuming there's a whole heap of thorium in the mine where the levels from what I've seen in the announcements appear to be minimal, again a geologist report is needed to determine the Environmental impact of pumping the water straight out to sea.
This is a speculation thread, how are we to know what the water contains. Would like to see your facts and research on this thread regarding your opinion on where the water comes from. It seems nro you haven't participated in sharing, rather you are just asking randoms on the internet.
(20min delay)