it took about 6 hrs, the material had built up for over a year, so it actually represents several hundred thousand tons of material concentrated down to about 2 ton.
My sluice isn't large enough, 20"w x 40" L, I'm making a larger one that can handle more material, 24"w x 6 ft long. I believe my recovery could have been better, my box was over loaded too often. I hook it up to a drain on a large tank where the heavies collect, and it can be hard to control the feed rate.
Look for an update in a couple months.