I think there was some free gold that was dropping to the bottom...

I think there was some free gold that was dropping to the bottom of the tanks, when they tested the sludge it had 1kg of gold per ton so they tested a pilot gravity plant to remove the free gold before it went into the system.
That was my understanding, correct me if i am wrong.

Another poster on here seemed to think it was lunacy to install a gravity plant, he did seem to basing his research on hotcopper post's.