This is a typical Statist opinion. Since when were the people to work for the State ..."it has little upside for the state and a lot of downside." The State is to work for the people!! However in fact,suction dreding can and  does have upside for the  state. 1) it provides some employment and revenue for the 2151 permitees 2) it actually pulls mercury out of the stream bed (if it is there) as it will be amalgamated to the recovered gold or will be amalgamated during the screening / sluicing process. 3) dredgers usually leave  well sorted (look up the geologic term) piles of gravel which make good spawning habitat for salmonids and other fish species. 4)dredging primarily occurs in the salmonid  non-spawning season and can add nutrient and mico-food to the other fish and non vertebrates in the stream.