News

Details

Written by: Angela De Palma-Dow

Published: 06 November 2022

Dear Lady of the Lake,

We just moved to a house near the Oaks Arm and I have heard there is concern with mercury on Clear Lake. Is it safe to go fishing and swimming? When will the mercury be cleaned up and how do I receive updates?

Thanks!

— Musing about Mercury

Dear Musing,

Thanks for this question and for your concern. The history of Mercury and Clear Lake is complex. I could probably write several books about the Sulfur Bank Mercury mine (hereinafter referred to as “the mine”).

Today’s column is really a brief introduction to the history of mercury in California, including in lakes and reservoirs, and Clear Lake, and the current efforts for clean-up by the United States Environmental Protection Agency, or U.S. EPA.

I also will not be covering in detail the complex impacts the mine has had, and continues to have, on the adjacent Elem Indian Colony, but I recognize and acknowledge that these impacts are significant and severe, and the Elem people deserve a robust remediation and compensation strategy to continue to live near and on the Superfund site.

Like much of the Golden State’s recent history, post-settlement growth, development, and economy of the state was long built on the exploitation of native peoples and the degradation of natural and cultural resources. While the mine has been credited, at one time, as one of the most profitable in the state for mercury, it can be strongly argued if the cost was worth the price.

For more information on the Elem perspective, experiences, and proposed solutions please visit the Elem Environmental Protection Website here.

What is a Superfund Site?

The basic definition of a superfund site is when a site, due to a previously occuring activity, poses a threat to public health and / or the environment and the responsible party (owner, manager) is no longer able to conduct appropriate clean up or mitigation. Usually, this occurs when a business has been polluting, such as dumping waste illegally, and then the company goes out of business, leaving behind a polluted site with no responsible party to conduct, remove, clean-up the waste, or remediate the pollution.

The waste itself, or it’s residue, can be hazardous or toxic and prevent people and wildlife from safely using the land or water, and so the site becomes a candidate for the federal Comprehensive Environmental Response, Compensation and Liability Act of 1980, or CERCLA, commonly known as Superfund. Sites that pose the greatest potential threat to public health and the environment are put on the National Priorities List, or NPL. The list can be viewed as a map here.

The NPL is the U.S. EPA's list of the most serious uncontrolled or abandoned hazardous waste sites identified for possible long-term remedial response under Superfund. Sites included in the NPL are mostly based on a score the site received under the Hazard Ranking System.

The Sulfur Bank Mercury mine was listed in 1990 and has a score of 44.42. The ranks are based on a scale of 0 to 100, based on the actual or potential release of hazardous substances from a site through air, surface water or groundwater.

Money from Superfund can be used for cleanup only at sites that are on the NPL. However, while the Superfund FUND, used to be mostly supported by oil and chemical taxes, expiration of those taxes occurred in 1995, leaving the taxpayers and general fund to fully support the program.

However, the recently passed Infrastructure Bill includes about $3.5 billion in cleaning up Superfund sites, and other hazardous properties like Brownfield sites, and reinstates the Superfund taxes on oil and chemical companies, making it one of the largest recent investments to address legacy pollution.

This also is probably good news for the Sulfur Bank Mine Superfund Clean-Up site, as funding shortfalls have been referenced as barriers to remediation completion.

Much to know about mercury

Mercury (Hg) is a naturally occurring chemical element. It used to be known commonly as quicksilver and has historically been used in such applications as thermometers, barometers, manometers, float valves, mercury switches and relays, and fluorescent lamps. Mercury was also used in hydraulic mining, to increase gold and silver yields.

These days, many of the above applications have utilized alternative elements or materials to replace mercury, as mercury can lead to significant health concerns if someone becomes exposed. Mercury poisoning results when someone is exposed to mercury in its liquid form through ingestion, mercury vapor inhalation, or through water-soluble forms such as methyl mercury or mercuric chloride.

Mercury poisoning can lead to potential brain damage, and permanent lung and kidney damage. Chronic exposure can lead to death.

In 2014 the US EPA aimed to fully eliminate the use of mercury in dental offices throughout the Country and in 2017 the U.S. EPA approved mercury limits in California waters and fish tissues to protect human health and aquatic wildlife.

Mercury is unique from other elements in that it retains its liquid form under standard, or everyday normal conditions of temperature and pressure, which makes it extremely pliable for common use applications as listed above!

Mercury history in the Golden State

In California, mercury was historically used to improve hydraulic mining efficiency since mercury creates an amalgam with gold and silver. Basically, when miners added mercury to flowing water washed from mine site, in sluices or troughs, the mercury would readily attach to the gold or silver, making the desired elements heavier so they would sink out of the water and separate from other gravel and sands materials.

This process improved the recovery rates of gold and silver mining. After collection, to separate the gold or silver from the mercury, the amalgam was heated, the mercury vaporized leaving behind only the gold or silver. The vaporized mercury then became airborne and both more easily inhaled and released into the atmosphere.

Mercury mining was conducted to harvest enough material to provide for the booming industrial age in California, and other western states, but also to improve gold and silver mining.

In fact, during the California Gold Rush, gold miners used over 26 million pounds of mercury, and research estimates suggest that at least 13 million pounds of that mercury were released into the environment, mostly through waterways.

Mercury in lakes and reservoirs

Mercury contamination in lakes and reservoirs in California is not unique to Clear Lake. Due to the heavy and widespread mining activity across the State that transported mercury to surface sediments and waters, most, if not all of the waterways in California are considered contaminated by mercury.

In fact, the Office of Environmental Health Hazard Assessment, or OEHHA, has a blanket fish advisory recommendation for all California lakes and reservoirs for a majority of the most commonly fished species and site specific advisories, such as this one for Clear Lake.

Studies of sediments in river flows during flood events has led researchers to predict that for at least the next 10,000 years, mining legacies in California will continue to release mercury-laden sediments into the environment, including waterways.

Mercury deposition is also a pathway for mercury to enter waterways, through rain and snowmelt. Mercury can become mobilized into the atmosphere during coal-combustion electrical power generation activities. Majority of this deposition occurs in the eastern and mid western United States.

You can track mercury deposition in your area by following the Mercury Deposition Network.

The history of mercury in California Lakes and Reservoirs is complex, and research is still ongoing to understand the full impact mining has had on ecological systems.

For more information I suggest these resources:

“Statewide Mercury Control program for Reservoirs”
Available: https://www.waterboards.ca.gov/water_issues/programs/mercury/reservoirs/docs/factsheet.pdf

“ Mercury Contamination: Toxic Legacy of the Gold Rush Assembly Natural Resources Committee March 24, 2014 Hearing Background Paper” Available: https://antr.assembly.ca.gov/sites/antr.assembly.ca.gov/files/hearings/Background%20paper032414.pdf

“Mercury and methylmercury concentrations and loads in the Cache Creek watershed, California”
Available at: https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1497&context=usgsstaffpub

Legacies of the Sulfur Bank Mercury Mine on Clear Lake

The mine is currently located in Clear Lake Oaks and stretches about 1,300 feet of shoreline on Clear Lake. The mine site contains a 160-are abandoned open-pit mercury mine, which is spring-filled with water and called the Herman Impoundment.

Note that the mine was not a hydraulic mine, but a pit mine. Pit mining, also known as open-cast or open-cut mining, is basically surface mining in descending fashion, down into the earth, as opposed to ascending fashion of surface mining on the side of a mountain or hillside.

The mine was mined for sulfur than mercury, intermittently, between 1865 and 1957. Mercury mined from the mine was transported around the state and used in hydraulic mining processes and in industrial applications.

After removing sediment from the pit, and mercury or sulfur was extracted, piles of removed sediment was dumped around the mine, sometimes into piles, called tailings, along the surrounding hills or into the lake or along the shoreline. The mine site has about 150 acres of mine tailings, which equates to about 200 million cubic yards of mine waste.

In general, the site geology, and surrounding sediment, is rich in mercury, which is why the site was selected as a mine location in the first place. Further human activity and modification of the area has allowed the mobilization of mercury from deep in the sediment to the surface where it can pose more contamination risk to humans and wildlife, and flow into the lake easier.

To complicate the issue, the initial clean-up solution, which created a wall of rock and sediment materials between the pit mine (i.e. Herman Impoundment) and the lake was constructed of waste rock from the site. This is called the Waste Rock Dam.

The Herman Impoundment, which sits higher in elevation than Clear Lake, and is spring fed, facilitates the mercury pathway into the lake. Gravity moves water from the impoundment through the contaminated soils and sediments of the waste rock dam; mercury is still slowly leaching from the mine site into the sediments at the bottom of the lake.

For the most part, mercury will stay adhered to sediments, and won’t be an exposure risk in the water itself. Swimming and boating are not at all hazardous in the Oaks arm area around the mine. Recreating in the sediments or soils at the site, or directly adjacent, should be avoided.
Please refer to this 2022 US EPA factsheet “The Sulphur Bank Mercury Mine Site: Arsenic and Mercury Risks."

Mercury exposure in water can occur when the mercury becomes methylated, under low oxygen concentrations in the water column, and moves into the water column where it can be consumed by fish. Fish and shellfish that live in, feed in, or habitat the sediments, are also more likely to ingest and become part of the mercury pathway.

The process of mercury moving from the sediments into fish, or living tissues, is called biomagnification. Biomagnification is the transfer of mercury in the fatty tissue of organisms up through the food web.

Basically, mercury transports through the tissue of one fish and is absorbed into the tissue of another fish, or human, when that fish is consumed. The larger the organism, the larger the amount of mercury potentially can be consumed.

Due to the contamination sourced from the mine, and the impact on the local tribal and Lake County communities, the site was added to the Superfund cleanup program in 1990. Since this time, the EPA has completed eight clean-ups to protect human health and the environment.

However, mercury is still present in fish in Clear Lake and in sediments near the mine, and continues to seep into the lake from the Herman Impoundment through the waste rock pile dam.

Future clean-up efforts

According to the Sulfur Bank Mine US EPA Superfund Site Team, there is a comprehensive plan to conduct the remaining clean-up on the Sulfur Bank Mine site. This team wants the community around Clear Lake to be involved and participate in this planning, so local concerns and perspectives are considered and included.

The general timeline for the Clean-up is as follows:

• Fall/Winter 2022: Final cleanup plan for the on-land mine part of the site presented to the community.
• 2025-2028 (estimated): Start cleanup of on-land, mine part of the site.
• Ongoing: Continue studying lake and sediment to see how best to control the mercury.

The proposed schedule and approach to the remaining clean-up will include a proposed cleanup plan, released sometime this month (November 2022, called a “Proposed Plan”) for the on-land mine part of the site.

The U.S. EPA communication and outreach team will conduct several open house, town-hall and virtual events where they will explain how the plan will protect human health and the environment.

After the U.S. EPA releases the plan, they will notify the community via newspaper, fliers, radio, website, postcards. They will also post a youtube presentation and open a 90-day public comment period. It’s the intention of the U.S. EPA to host several public engagement opportunities, with events dates, time, locations, and accessibility information being posted on their website and sent out to local media partners.

You can reach out to the U.S. EPA Sulfur Bank Mine team directly by contacting their Community Involvement Coordinator, Gavin Pauley, Region 9, at (415) 535-3725 | This email address is being protected from spambots. You need JavaScript enabled to view it..

To learn more about the U.S. EPA Sulfur Bank Mercury Mine site clean-up and progress and to be added to the Superfund Site’s mailing list, visit this page.

This year there have been two presentations to the Lake County Board of Supervisors by the Sulfur Bank Mine Sueprfund U.S. EPA team, you can find them here and and the County of Lake You Tube Channel.

April 19, 2022
https://lakecounty.granicus.com/MediaPlayer.php?view_id=1&clip_id=604&meta_id=201804

Sept. 20, 2022
https://lakecounty.granicus.com/MediaPlayer.php?view_id=1&clip_id=573&meta_id=186098

Sincerely,

Lady of the Lake

Angela De Palma-Dow is a limnologist (limnology = study of fresh inland waters) who lives and works in Lake County. Born in Northern California, she has a Master of Science from Michigan State University. She is a Certified Lake Manager from the North American Lake Management Society, or NALMS, and she is the current president/chair of the California chapter of the Society for Freshwater Science. She can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..