For all dredging permits you'll first need to visit www.idwr.idaho.gov go to the "stream/dam/flood tab", from there a drop down menu will pop up when you hover over the tab and choose "stream channel protection program"
once opened choose the "map" tab and locate the section of river you wish to dredge. Once located you can find out the season you are able to use your dredge on. Save or write down the river section & season. From there you will go to "Recreational Mining Permits" then click on "Forms" if you are unsure of which form to complete given the river channel you are using give Kass Jones a call at 208-287-4800 he is great help over at the IDWR.
I have included below the season for the section of river this claim is on, however please make sure it does not change from year to year.