I was gold mining in southwest Montana years back and we were working a low grade property that had lenses of rich pay gravel throughout a 10 ft pay zone. We had to really push the material through. As you can see I love gravel pumps.
Gravel pumps on stationary wash plants will just give you a lot of leeway with your tailings disposal. If you just need to get it to a previously mined pit, it is cheap and helps keep your overhead down.
If you have a secondary recovery system you can pump the gravel to the additional recovery plant. The gravel pump really is a good scrubber of the fines. This is a super simple setup and I recommend it for most sluicing type operations. You can size it up or size it down. This is of course contingent on your values and your spreadsheet requirements.