Note bene: Under construction. Any info on mercury mines would be appreciated. FWIW, every time I make an edit, Blogger keeps taking this post down, claiming it "violates community standards."but it doesn’t specify what it wants me to remove. I don't see how historic information from public sources violates any standards. All the research, and the writing is my own, and the photos too. Most of the information and maps were created via government funds, and should be copyright free or fair use. Plus I've provided the links.
According to the California Office of Environmental Health Hazard Assessment (OEHHA), there is an fish advisory or warning that Nicasio Reservoir mud contains methyl-mercury, as does Bon Tempe Reservoir on the slopes of Mt. Tamalpais, which hosted several historic mines, including mercury, copper, gold, and even a nickel mine.
And I assume that all the rest of the Marin Municipal Water District (MMWD) reservoirs (our drinking water supply) also contain trace amounts of some form of (inert) mercury too as they’re all downstream of Bon Tempe dam and empty into each other, exiting via Kent Lake into Lagunitas Creek that drains into Tomales Bay. Naturally occurring mercury oxide does not enter the food chain the way methyl-mercury does.
But at the Nicasio Reservoir methyl-mercury pollution is significant enough to trigger OEHHA advisory warnings about cumulative mercury poisoning from carp, sunfish, black, and large-mouth bass species (apex predators such as bass contain the most cumulative methyl-mercury in their systems). Why Nicasio? it doesn’t butt up against any known mercury mines, not like the unrelated Solejoule Reservoir watershed to the north (there’s an OEHHA advisory warning for black bass and crappie. There’s more on Solejoule dam methyl-mercury pollution below.)
I don’t know if Halleck Creek, a tributary of Nicasio Creek that feeds the reservoir, also has mercury in it. If so, then there’s probably an old mine shaft or two somewhere up-canyon on Big Rock Ridge. There is Lunny’s (LaFranchi?) gravel quarry across the way, but I don’t think they use cyanide for rock blasting! Nor are they transporting mercury ore for their gravel business as it wouldn’t be very good for business.
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| Note the MMWD mercury warnings are in English, Spanish and Vietnamese. |
The fish warning signs along the Nicasio Reservoir serve as a grim reminder that mercury poisoning is cumulative. Mercury oxide is a naturally occurring inert mineral in the soil, but there are numerous cinnabar mine tailings throughout Marin and Sonoma counties that have added to the mercury levels of our reservoirs, not to mention, Tomales Bay. (Why I won’t eat Tomales Bay oysters….)
Red earth is often a sign of the presence of cinnabar (Remember Napa’s Silverado Mine on Mt. St. Helena, made famous by Robert Louis Stevenson’s 1884 novel, The Silverado Squatters). And if there were heat-processed mine tailings to extract the mercury, then the leftover mercury particulates leaches out of the rock tailings whenever it rains.
But some of those old red earth mine sites were hematite, a type of iron, not cinnabar—like the Sausalito mine and the prehistoric site on Mt. Burdell. Inert red dirt. Sometimes a red rock quarry is just a red rock quarry.
That said, there are also several historic cinnabar mines in Novato (an unnamed claim, the Mazza Ranch Prospect, and Gaul mines), and other mine sites in West Marin. I remember seeing an old mining map of Bolinas Ridge dotted with several old cinnabar (and copper) mining claims. And another potential cinnabar site is on Elephant Mountain near Black Mt. Ranch and Platform Bridge, though only a gravel quarry is listed on the other side of the mountain.
Mercury ore mined in California, originally used for silver and gold extraction, was processed in high-temperature smelting ovens. Those unstable leftover tailings are what has caused the mercury runoffs into our watersheds, including in the San Francisco Bay. But Tomales Bay has higher mercury levels than San Francisco Bay—and not from naturally occurring cinnabar deposits, as the mineral mercury is inert unless it’s been heated and extracted.
The methylmercury is coming from somewhere. Question is, where?
Moving north to an adjoining Tomales Bay watershed (Walker Creek), on Hicks Valley Road, as you make the turn past Lincoln School, there’s a rock quarry at the top of the ridge to your left, (Hammock Hill) the exposed Franciscan rock is as red as can be. It looks like mine tailings galore. But not even a rock quarry is listed on that hill, though I can clearly see it from the road.
Rancher Sam Dolcini said it was a historic gravel pit used for making roadbeds. However it’s also a fair distance from Hick’s Mountain (see mining list) and Hick’s Valley Road. And it’s pretty darned red for Franciscan strata. It could also be an old Native American hematite mine.
Question is, why did the Marin County road builders go all the way up that mountain for gravel? Surely there were more accessible rock outcrops? Maybe it was a speculatory dig that didn’t pan out—the entire northern Marin region has several mercury mines.
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| Sweetwater Springs mine on Mt. Jackson. Michael Kiesling photo |
A little retrospective on reusing mine tailings, which was viewed as an easy source of cheap gravel. In Sonoma County, ca. 1974, the Guerneville sewage plant used mercury-laden tailings from an abandoned mine on Mt. Jackson for roadbeds. (I once hiked up to the Sweetwater mine via an eroded mule trail off Sweetwater Springs Road.) Luckily, it was a tempest in a teapot, the tailings were found to be inert, there was no leeching mercury. (See Mercury Rising 1999). The unlisted Hicks Valley rock quarry on Hammock Hill could be an old prospector site, and a gravel pit for road bed material. Both.
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| Hammock Hill, Hick’s Valley Road c Maureen Hurley 2020 |
There’s another rock outcrop that was probably also mined for roadbed material at the Point Reyes-Petaluma/Red Hill Road and Nicasio Valley Road junction at the old Gallagher Ranch. Geoff Davis said there was also cinnabar present there too, but it looks like it’s a limestone outcrop, or a ribbon chert reef, not cinnabar. Half the rock outcrop is gone, and other outcrops were left untouched. Apparently the host rock for mercury ore is serpentinite from the Upper Jurassic period. So, wherever there’s serpentine? All of West County!
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| This outcrop was twice as big, was it used for gravel or a mercury prospect? |
Also within the Walker Creek watershed, the worst (and latest, 1970) mercury mine offender of all was the Gambonini Ranch mine complex on Walker Creek Road. The Gambonini Ranch family was not the problem, PG&E was, as they, or rather a sub-contracted mining company, Buttes Gas & Oil Co., leased at least four mines—the Gambonini, Turner, McFarland and Buena Suerte mines. When the mercury ore ran out, and the mines were “closed,” Buttes Gas & Oil Co. got off scot-free by claiming bankruptcy in 1985, leaving the state of California holding the bag, and liable for a massive Superfund cleanup.
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| You can explore the types of mines at Minedat. Most are mercury mines. |
(You can explore the types of mines in the North Bay at Minedat. Most are mercury mines. See also the the Cycle, and Franciscan mines. I know they exist, but can’t find supporting data, the adjoining Edwards mines (Panco No. 1; Chileno Valley; Bueno Chilano; Chileno Valley), and Bently Ranch.) And there is the mercury Bivalve Mine, near Soulajule Dam, and another mercury mine, Petaluma Mine (Superior Gypsum Company Mine), on Red Hill Road.)
Not only was liquid mercury useful in extracting silver and gold ore from mine tailings during the gold rush, it was used for barometers, thermometers, clock pendulums, dental amalgams, auto parts, batteries, plating silver mirrors, fluorescent bulb filaments, and delicate electronics. The military also used liquid mercury for calibrated gauges, ammunition primers, and detonators, so it was a valuable restricted resource. (Military mercury uses PDF.)
Until recently, liquid mercury was also used in the construction of legacy PG&E electrical transformers. Later, PCB laden oil was used. (Sources of PCBs and Mercury contamination). Curious, I can’t find information on how PG&E used mercury. I found this downloadable PDF from Internet Archive Scholar, The Needs of Miners: Political Ethics, Mercury Abatement, "The need for a global mercury pollution reduction strategy emerged from scientific revolutions of the 1950s and 1960s.” Mercury was becoming increasingly scarce during the 1960s, which drove its value through the roof.
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| Cool old trucks at the Gambonini Ranch c Maureen Hurley 2019 |
Back to the Gambonini Ranch story, in 1964, a PG&E subcontractor, Oakland-based Buttes Gas & Oil, did a blitzkreig open pit mining job and in 1970, when the price of mercury dropped, they folded shop and left the open pit mercury mine tailings exposed to the elements behind an earthen dam that epically failed during a series of storms in 1982—they never sealed the mines, nor capped the tailings.
Meanwhile, in 1977, Buttes Gas & Oil claimed bankruptcy and suspended operations in California, leaving the ranch owner Alvin Gambonini holding the bag—environmentally speaking. When methylmercury began showing up in Tomales Bay, it triggered a $3 million Superfund cleanup in 2000. The company had leased the land from Alvin Gambonini’s father from 1964 to 1970, and no one ever disclosed to the Gambonini family the potential dangers involved.
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| San Francisco Bay Regional Water Quality Control Board, 2012 A state funded agency |
Few knew about the danger or full extent of the mercury pollution in the North Bay until significant amounts of methylmercury began showing up in Tomales Bay in 1999 after a series of back-to-back severe storms created a deluge runoff.
“The mercury, in a particularly toxic form called methylmercury, was discovered in a test of Tomales Bay fish conducted in 1999 by the San Francisco Bay Regional Water Quality Control Board.…The mercury is believed to have infiltrated Tomales Bay from an open-pit mercury mine located 6 miles upstream from 1968 to 1972. The mine is now an EPA Superfund site.” —Mercury Warning For Fish / 7 Tomales Bay species show contamination, 2000
Since 1964, every time it rained, it means that methylmercury spilled into Tomales Bay. Soulajule Dam, constructed in 1980, conceals an environmental atrocity. Luckily, Soulajule is a reserve reservoir not used for drinking water. The old mines are above waterline, but the lethal tailings around the reservoir are the real problem. And dare I ask the question: what actual earth was used to build that dam?
"If you take a sample of soils anywhere in this county, you will find mercury in it, but in the form of oxide, so it's not a dangerous element," geologist Dylan Whyte says.“The mine site, leased to the Buttes Gas & Oil Co. by Gambonini's parents, is across Wilson Hill Road from the ranch house six miles southwest of Petaluma, and up a steep ridge.” Mercury Rising 1999.
From MMWD: “The District also can transfer Soulajule Reservoir water to other District locations, as needed.” How? I don’t imagine that MMWD would transport water from Solajoule to Nicasio via truck. Someone suggested the water can be moved overland via stock ponds. If mercury oxide is inert, then it suggests that the methylmercury isn’t coming from natural sources. So where is the mercury coming from?
Reference Notes and questions.
In Chileno Valley, I found that there are at least five mines; four Edwards Ranch mines: Pancho No.1, Chileno Valley (2), and Bueno Chiliano. Also the Corda mine. Are all the mines located on San Antonio Mountain? There’s a mine reference to the mountain west of Wilson Hill Road. It seems the tailings were processed at the mother site, the Gambonini Ranch mine.
Does the drainage for the Edwards mines drain into Chileno Creek, downstream of Laguna de San Antonio? Or to Walker Creek? Either way, most it eventually drains into Tomales Bay. The Corda mine drainage goes east into San Antonio Creek to the Petaluma River. Laguna (Lake) de San Antonio is the crest of that watershed. All the rest go into Tomales Bay.
There were several gold and cinnabar mines in San Rafael, one on San Rafael hill near Lincoln Ave., (same?) in Terra Linda; and more mine shafts near Santa Venetia (Skettrini Fire Road above the Civic Center?), on the San Pedro Mountain Preserve above Dominican University. I hiked up San Pedro Ridge via Aquinas Street in 2020 which led to the writing of this blogpost. Too bad the nuns had to sell off their land. Worth more than gold now.
The name Gold Hill fire road near Henry Barbier Memorial Park (near the Nike microwave tower) should be a clue that the San Pedro ridge complex hosted many mines. Another reference to (same?) mine above the Country Club, and at China Camp—all are on San Pedro ridge I suspect there were more mine shafts than actual producing mines.
There were at least a baker’s dozen of active mercury mining districts in Muir Beach, Tomales, Inverness, Point Reyes Station (I wonder if this is the mine on Black’s Mountain), Lagunitas (Deer Point on the north slopes of Mt. Barnabe near Nicasio), Chileno Valley (5 mines), and six mining sites in northern Marin county within the Petaluma mining district, including the west Mayacamas mine. I had no idea there was even such a thing as the West Mayacamas mining district.
I found these links useful.
Marin County mercury mines The Diggings uses BLM data, a public source.
Hicks Mountain, Marin County, mindat.org, Hudson Institute of Mineralology, an interactive map!
Soulajule Reservoir and Arroyo Sausal Methylmercury Control Project
Mercury Rising, Abandoned mercury mines leave toxic legacy in North Bay Jan 1999
Toxic mercury cleanup ordered in West Marin. Mercury mines in NW Marin include Gambonini, Chileno, Franciscan and Cycle mines. Soulajule Reservoir was built on top of Franciscan and Cycle mines tailings…. Buttes Gas and Oil Co. closed the Gambonini mercury mines in 1970. They built an earth dam to contain mercury sludge and tailings, but for more than two decades mercury polluted Walker Creek, settling in the mud of Tomales Bay. It became a superfund cleanup site. Mercury was used in thermometers, dental fillings, fluorescent lights and military gauges. The military listed mercury as a controlled substance but it was removed it in 1970, and the mercury market plummeted.
Thank you Michael Kiesling for use of your Sweetwater photo, ca. 1988, I too hiked to the mine and had to spent the night out there as my friend thought he could read a topo map. Never trust a man with a topo map.
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| Managing Inactive Mercury Mine Sites in the San Francisco Bay Region p.27 |
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