Thanks, found it, indeed it's hard to miss if you're looking for it.
There still is work to do! I've been there the other day mining, and taken a look: the first part from Paramount Lake is wide, but the second part of the tunnel, to Harvest Moon, is one-tile wide and we need to make it 4-tiles. I've started there mining stone till servers shutdown. Lots of work still needed to become passable by ships for all its length, and as I understand, help is welcome!
There's stone, silver veins all around, some iron vein, and organizers have taken care to bring on place the necessary (bsbs, forges, meals, stuff).