. >> reporter: for modern small scale miners like ron larson, the most effective tool is a fairly newntion known as the hydraulic dredge. >> locked and loaded. >> a hydraulic dredge is essentially a floating platform with a power plant that supplies air and power to move water over a riffle box, to sort out the heavy material. gold is heavier than any other mineral in the stream and the only way to get the gold is to remove what is called overburden. >> reporter: to strip away this layer of rock and sediment, miners are equipped with diving gear and a high-powered underwater vacuum. also known as suction dredging, this method allows miners to go through as much as forty times more sediment than non-motorized mining. but growing concern over possible environmental impacts, has caused lawmakers in california, oregon and idaho to take action to restrict it. that leaves washington as one of just a few western states to allow dredging in most of its waterways, setting up a key battle between small scale gold miners. >> there's a dredge right over here. >> oh yeah. >> reporter: and the acti