Dredges can harm streambanks and streamside vegetation as the equipment is hauled in and out of the water, or used to dredge beneath streambanks.That’s why restrictions, limitations or statewide bans have been put in place in Idaho, Oregon, California, and other western states. Fisheries biologists, hydrologists, and others agree that suction dredge mining can be harmful to fish and threatens water quality.

Mercury can be released into the water column, threatening public health, aquatic species, and downstream users.Holes created by the dredging can persist and change river hydrology, leading to downstream erosion and creating dangerous wading conditions for boaters and anglers.Gravel deposited behind the dredges can create unstable spawning beds, which can be attractive to fish yet fail to provide the stable substrate that eggs need to survive.Sediment discharged by the dredges can smother fish eggs.Suction dredge mining can wreak havoc on fish habitat and water quality in many ways. Dredge miners chew their way through the bed of the stream, using their dredge, along with crowbars, picks, hammers, and chisels to break up the bedrock in search of small flecks of gold – harming our water in the process. The dredged material (sediment, gravels, rock, and water) is then discharged through a sluice box on the back of the floating dredge, capturing the gold and spewing sediment and gravel back into the water. The miner dives to the bottom of the stream and uses a hose to suck up gravel and sediment. Suction dredge mining is a form of recreational gold mining that utilizes a high-powered floating vacuum. In response to that story, we’ve received a number of questions asking what dredge mining is, if it’s legal in Idaho, and why ICL cares about it. Suction dredge mining has been in the news lately, with a federal judge in Idaho recently levying a record $150,000 fine against an out-of-state miner who refused to follow rules that protect the South Fork Clearwater River and the sensitive, threatened, and endangered fish that live there.

Dredge mining scars