The link below is to a report studying all possible effects of suction dredging on stream habitat, water quality and biota. It was prepared for the U.S. Environmental Protection Agency.
This may be far more than most want to read (86 pages) but it will certainly provide anyone interested with all the info they ever wanted about the impacts of gold dredging. One thing to remember is that this study was performed on the Fortymile river in Alaska. What they are studying is commercial gold dredging and the dredges there are 8", 10" and 12" class dredges. The largest dredge allowed in Washington is only a 5" hoze size.

Draw your own conclusions...

http://www.swrcb.ca.gov/water_issues/pro...ussian_1999.pdf

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