Suction Dredging and Mercury

The basis for SB670, AB120 and the California Department of Fish and Game regulations that attempt to drive suction dredgers out of the rivers is weak science and flawed analysis relating to both mercury and frogs. These bills and the structure of the regulations were driven by extreme environmental groups with no interest in the truth, facts or science. They are pursuing their own agenda of a Utopian landscape seen through pastel colored glasses. Their vision of the environment disregards a thousand years of mans interaction with his environment and attempts to impose a vision of the environment where man is only an observer In this article the WMA will highlight the presented evidence on mercury and dredging and next month we will cover the Sierra Mountain Yellow Legged Frog.

Suction Dredging and Mercury

The mercury analysis in the SEIR is based on the picture to the left. Does this look like a dredge to you? Based on the experiment to the left the SEIR concluded that a small number of dredgers could produce more mercury in the watershed than the entire spring floods could produce.

Interesting – but is it true?

Not even close. The contraption in the picture was used to power spray bedrock that had been dug by hand and used the water in the tank to blast the bedrock and then suction up the resulting mercury from the bedrock. Notice the motor and pump attached to the hoses in the picture. The water contaminated by mercury was forced back through the impeller thousands of times causing the mercury to become atomized. We all know that mercury does not go through the impeller of the dredge even one time, let alone thousands of times. Secondly, the experiment had no sluice box ensuring that no mercury was recovered. All the mercury was smashed into extremely tiny particles, mixed with very fine sediment and then measured for mercury to sediment levels. This is what passes for government science, it’s very weak science, but hey, it’s something they can write a paper on figuring miners weren’t smart enough to see the flaws in this.

The entire conclusion of mercury as “Significant and Unavoidable” is based on this experiment. From this experiment the SEIR then concludes that a very small number of dredgers would be able to pollute the entire river. We evaluated this conclusion and found that no number of dredgers could ever possibly approach the natural loading of the river under any circumstances. The graph below provides the differences in bad science and the real world impacts.

graph of dredging hours
SEIR versus Real Hours Required to Reach Natural Load

OK, we know the graph is pretty hard to decipher, but this is fairly complex stuff we evaluated and tried to distill down to one chart. Let’s cut to the chase: The SEIR states that only 1,100 hours of dredging time would be required to put as much mercury in the water as the spring floods do; our analysis says that 2,800,000 hours of dredging would be required – with everyone dredging in the exact same spot. Is this realistic?

Let’s be clear, we’re not arguing mercury is a good thing. We’re arguing that the mercury produced by a suction dredge, as measured in government sponsored testing, is insignificant. We, at the WMA, are prepared to challenge the CDFG suction dredging regulations when they are posted. We believe, that despite evidence presented that contradicts the SEIR findings that the final regulations will not differ from the draft that was posted in March of this year.

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