Hey Joe, The answer is yes, when you are not working your shift you are free to do any mining you want, dredging, highbanking, sluicing.
And no the paydirt piles for the dig are just for the highbankers that are running for the dig.
But there might be other common piles around the holding ponds, that are available to members that are not participating in the dig, and these you should be able to pull from. Or you can go find your own area.
One thing about the creek, there's been a lot of rain lately, so there's the possibility of the creek being refreshed with "flood gold".
Paul