Above. USGS personnel conducting suction dredge testing on the South Yuba River.
In April 2015 the Western Mining Alliance issued several requests for information on mercury to different agencies. One of these agencies was the California Regional Water Quality Control Board. The WMA submitted a Public Records Act request for all mercury sampling conducted from the year 2000 to present for the Yuba, Feather and American Rivers. The purpose of the request was to evaluate mercury levels in the water prior to the suction dredging ban, and after the ban.
Although the Water Board has been conducting mercury sampling for decades in these rivers only data for the years 2000 to 2009 were provided. In a follow up communication with the Water Board they confirmed they had no data after 2009, the exact year the suction dredging ban went in place.
In the 2012 California Department of Fish and Wildlife (CDFW) suction dredging Environmental Impact Report (EIR) the State argued there was evidence suction dredges contributed mercury loading to the Water Sheds. They based this statement on one year of sampling which showed a slight decrease in mercury sampling from one year to another, but the EIR also stated additional sampling of no-dredging years would be required to confirm their theory.
It appears all too convenient for the Water Board to stop their sampling program the exact year of the suction dredging ban making it impossible to discredit their theory. If mercur was the problem they believe it to be one would think the mercury sampling program would have continued. But, according to the Water Board, it didn't.
Western Mining Alliance president Craig Lindsay believes it just a little too convenient. "Wouldn't you think if dredging was really a mercury problem the scientists would just be eageer to run out and confirm their theories." said Lindsay. "There can only be one of two answers," he continued, "Either the Water Board did do it, but they don't want us to see the results. Or they really didn't want to know what the data was without the dredges on the river."
This leads to the question of why they wouldn't want the data for mercury after the dredging ban. Data the Western Mining Alliance was able to obtain through a Freedom of Information Act (FOIA) request to the US Geological Survey begins to provide some answers.
"Mercury levels are going up." Said Lindsay. "The data we received from the UsGS clearly shows a sharp spike in measurements once the dredges are removed from the rivers. It's clear suction dredgers were removing this mercury before it had a chance to become harmful."
The data Lindsay refers to shows a significant increase in measured mercury of insects in 2012, when no dredges were running, versus earlier years which showed steadily decreasing levels of mercury in insects.
In the sampling data the same sites were selected which were also used to obtain the mercury measurements for the 2012 EIR on the South Yuba River. The sampling inclues 2007, 2008 and 2012. In the EIR the Water Board stated they had only one year of data to evaluate the effects of a no-dredging condition, but now they have six years, but they have failed to conduct any additional sampling during the dredging ban. The USGS did limited sampling and this sampling doesn't provide the results the environmentalists had hoped for, it's just the opposite.
In the Humbug Creek measuring site the sampling for three different insects shows a sharp increase of mercury levels as shown below.
Above. Chart showing mercury measurements in insects have increased since the dredging ban.
In the 2012 EIR the State pointed to the decrease between 2008 and 2007 as evidence dredging was linked to increased mercury levels. The Western Mining Alliance argued this drop was likely due to seasonal variation and had nothing to do with suction dredges. The State claimed since only one year of data was available this was the only conclusion they could reach. Now, with the addition of the 2012 data, a completely different conclusion is reached. Using the same sampling site as was used in the EIR mercury levels have actually risen since the dredging ban indicating suction dredges were an important factor in removing mercury from the watersheds.
The data for the Humbug Creek site wasn't the only site to show a marked increase in mercury. Mercury levels were found higher consistently across all sites despite no significant flooding having occurred to account for the difference.
Above. Samples of mercury levels in insects showing increasing mercury since the dredging ban. Location: Humbug Creek and South Yuba River
Another site on the South Yuba River frequently sampled for mercury because of the easy access is Edwards Crossing. Multiple years of sampling data existed for this site well prior to the suction dredging EIR and the data was easy enough to obtain. The Edwards Crossing site shows the same increase in mercury levels as the other upstream sites.
The evidence for mercury levels being associated with floods is clear. You don't need a PhD to see during flood events a huge spike in mercury is seen in the river. These major flood events disturb the mercury found at the bottom of the river in the hard packed sediments and release this mercury back into the watershed where it flows down to the lakes and reservoirs , and ultimately the Delta where it is transformed into a harmful type of mercury which can accumulate in the food chain. This harmful type of mercury, known as methylmercury, has the potential if ingested in large quantities to cause health effects. Although at the levels present in California watersheds there is no evidence of health effects, but researchers speculate it is possible.
The below chart shows mercury readings in the South Yuba River during a flood event compared to normal background levels.
With clear scientific evidence, and multiple years of data, it appears suction dredging results in lower mercury levels in the watershed, not higher. The suction dredging ban has resulted in increasing mercury levels while preventing the only removal of mercury from these watersheds. No link has been shown between suction dredging and mercury levels and evidence presented in the 2012 suction dredging EIR is pure speculation which has been attacked as poor science by multiple experts.
Suction dredging results in the removal of mercury from watersheds before it can transform into a harmful type. It is surprising even the environmentalists fail to see the environmental benefits of this.