Remediating mercury at Reclaiming the Sierra
Mercury runoff stemming from the historic gold mining that helped make Nevada County the community what it is today continues to provide an environmental challenge from waterhead to the bay and between, according to a Thursday panel discussion at the three-day Reclaiming the Sierra conference.
The mercury was put into the environment through loss from the mercury-gold amalgamation process that was used to siphon gold from the gravel. This proved effective in extracting gold, but it also led mercury to flow downstream, binding onto fine silts and clays. Between 10% to 30% of the estimated 26 million pounds of mercury used in the Sierra Nevada and Klamath-Trinity mountains alone is believed to have been lost to the environment.
Now, engineers, environmental scientists, governmental officials and policy makers are coming together to enact the Sierra Fund’s strategy to reduce mercury contamination at the organization’s three-day Reclaiming the Sierra conference.
The Sierra Fund, a nonprofit organization with the mission of protecting and restoring the resiliency of Sierra Nevada ecosystems and communities, launched its Headwater Mercury Source Reduction project in 2017 to promote region-wide and multidisciplinary collaboration in abating mercury contamination “from the Sierra to Sea.”
The conference, held Wednesday through today, featured panels that outline and expand on its four-pillar focus for mercury remediation: hydraulic mines and mine features; mercury in forest and land management; mercury-contaminated sediment in reservoirs; and mercury exposure via fish consumption.
The conference opened with a reception and art program on Wednesday and will end today with its “Mercury in the Headwaters” tour with stops at Combie Reservoir, Englebright Dam and Blue Point Mine discussing opportunities for ecosystem restoration.
Panelists and speakers included Sierra Fund program director Carrie Monohan, Eli Ilano of the Tahoe National Forest, Charles Alpers of the U.S. Geological Survey, Lori Copan from the state Department of Health, and author and scientist Jane Hightower.
The organization’s strategy, a living document meant to be informed and improved upon by research and collaboration, largely calls for inventorying and prioritizing sources of mercury contamination as the first step in their effort.
Strategies for remediating mercury sources in hydraulic mines and their features, for instance, call for “ground truthing” the database of sites and cataloging physical and chemical hazards at each site before prioritization. Practices would then be created to minimize soil erosion and the contact contaminated soil has with water.
A similar approach is called for in managing mercury in forests and land management, with identification and prioritization of mine-impacted forest lands based on fuel-loading, potential for erosion, potential for mercury transport or other factors.
Part of the challenge on this front is the lack of resources available to forest and land management staff at the Tahoe National Forest, which will soon only have one person to deal with mining and mineral resources issues, making the ability to rely on partners with a shared vision critical.
As an example of that, in order to treat mercury-contaminated sediment found in reservoirs, the group is working with the Yuba Water Agency to find the best use for accumulated sediment coming from mines that has found its way to the agency’s dams.
In 2017, the water agency had to mechanically remove more than 70,000 cubic yards of potentially contaminated sediment from its Our House Dam alone. With the help of Sierra Fund partners, the agency will look for ways to put that sediment to use in further mitigating mercury contamination.
The final stage of the group’s strategy is to reduce the risk of mercury exposure through fish consumption, which poses the largest threat to humans.
Reservoirs can act as bioaccumulation hot spots with mercury moving up in the food chain from plankton to predatory fish, becoming more potent in the process. According to the U.S. Geological Survey, methylmercury concentrations can increase more than 1 million times from water to top predators through bioaccumulation.
On top of the direct threats posed by mercury levels, Hightower reviewed medical literature which suggests the contaminant could have larger implications on other common health diagnosis like cardiovascular disease and diabetes.
More information about the Sierra Fund and their work on Reclaiming the Sierra can be found at http://www.reclaimingthesierra.org.
To contact Staff Writer John Orona, email email@example.com or call 530-477-4229.
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