The New Idria Mercury Mine encompasses 8,000 acres of land in the
Diablo Mountain range, incorporating the town of
Idria in
San Benito County, California
San Benito County (; ''San Benito'', Spanish for " St. Benedict"), officially the County of San Benito, is a county located in the Coast Range Mountains of the U.S. state of California. As of the 2020 census, the population was 64,209. The c ...
. Idria, initially named
New Idria, is situated at and 2440 feet (680m) above
mean sea level
There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set.
For a data set, the '' ari ...
. The area was, in the past, recorded in the US Census Bureau as a rural community; however, Idria has become a ghost town since the closing of once lucrative mining operations in the early 1970s.
[ New Idria, California]
In 1990, the
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...
(EPA) investigated the
mercury contamination level in soils, groundwater, surface water, and air of
Idria, and concerned with the impact that the
mining
Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...
industry had had on the local environment. However, the contamination was not ranked high enough to be listed on the EPA’s
Superfund Site List, nor its
National Priorities List.
On March 10, 2011, after the site had been reassessed in 2002 along with an expanded site in 2009, the EPA finally proposed adding Idria to
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
's
Superfund List.
Mercury, along with
heavy metals and
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
, were found in nearby
San Carlos Creek, Silver Creek and a portion of
Panoche Creek
Panoche Creek is a creek in San Benito and Fresno Counties, California, in the United States.
Historical names include Arroyo de Panoche Grande (Big Sugarloaf Creek)Mildred B. Hoover, et al. ''Historic Spots in California''. 3rd edition. Stanfo ...
at high
toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
level to
aquatic organisms and nearby populations. The contamination was also shown to be potentially threatening to habitats extending to the
San Joaquin River
The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
and
San Francisco Bay.
History
The
New Idria Mercury Mine was claimed in 1854, with the first brick furnace built in 1857. During the
California Gold Rush,
mercury was the key component to extract
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...
from
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
s. Mercury, a major component in the
cinnabar
Cinnabar (), or cinnabarite (), from the grc, κιννάβαρι (), is the bright scarlet to brick-red form of mercury(II) sulfide (HgS). It is the most common source ore for refining elemental mercury and is the historic source for the bri ...
-rich rocks in Idria, could be economically extracted to support nearby
gold mining
Gold mining is the extraction of gold resources by mining. Historically, mining gold from alluvial deposits used manual separation processes, such as gold panning. However, with the expansion of gold mining to ores that are not on the surface, ...
and processing operations. Idria eventually became the second most productive mercury mine in
North America, producing over 38 million pounds of mercury during its lifetime. Mercury mining operations ceased in 1972, with the closure of the New Idria Quicksilver Mining Company.
However, the environmental consequences of mercury mining remained well past the abandonment of the town.
Geology
The New Idria
Serpentine is a elongate
intrusive body, 14 miles long and 4 miles wide, surrounded by numerous former quicksilver mines. The Jurassic Franciscan
Formation
Formation may refer to:
Linguistics
* Back-formation, the process of creating a new lexeme by removing or affixes
* Word formation, the creation of a new word by adding affixes
Mathematics and science
* Cave formation or speleothem, a secondar ...
, consisting of
arkosic
Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar.
Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose.
Quartz is ...
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
, forms a discontinuous ring around this serpentine, or as inclusions. This New Idria
dome is exposed at the crest of the Coalinga
anticline
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
. The New Idria
thrust fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
is located along the northeast portion of this core, though
normal fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tecton ...
s are located along the southwest and west boundary. The New Idria Serpentine is the source of the quicksilver mineralization, and
chrysotile asbestos. Bordering this plug of rocks is the
Upper Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', th ...
Panoche Formation consisting of
silty
Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...
-
shale and
concretionary
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...
sandstone up to 20,000 feet thick. Most of the New Idria mine production came from the
hydrothermally altered shale controlled by faulting. Quicksilver deposits also occur in silica-carbonate rocks produced from serpentine, known as the "Quicksilver Rock" of California.
Cinnabar
Cinnabar (), or cinnabarite (), from the grc, κιννάβαρι (), is the bright scarlet to brick-red form of mercury(II) sulfide (HgS). It is the most common source ore for refining elemental mercury and is the historic source for the bri ...
is the chief
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
mineral.
Regional Mercury Reservoir
The land surrounding
New Idria Mercury Mine currently has an emissions flux of 9.2 ng Hg/m
2h, possibly lower than expected due to the amount of mercury confined to rock fractures and unit boundaries. The annual flux is around 18 kg per year. Since Idria has natural mercury reservoirs, it is important to factor in these background emissions in measuring the total impact from mining itself. As such, areas disrupted by human activity have been measured to contribute around 15% of these total (background included) mercury emissions into the atmosphere.
[Gustin, Mae Sexauer. "Are mercury emissions from geologic sources significant? A status report." Science of the Total Environment 304.1 (2003): 153-167]
Once abandoned, the New Idria Mercury Mine also discharged mercury-containing
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
(AMD) into San Carlos Creek, Silver Creek and a portion of
Panoche Creek
Panoche Creek is a creek in San Benito and Fresno Counties, California, in the United States.
Historical names include Arroyo de Panoche Grande (Big Sugarloaf Creek)Mildred B. Hoover, et al. ''Historic Spots in California''. 3rd edition. Stanfo ...
. AMD discharge accounted for about 50% of the water downstream from the mine and heavily impacted downstream ecosystems. It's estimated that AMD inputs into the surface water was 24 L/s during the six months of wet season and 5 L/s during the six months of dry season, with downstream unfiltered total mercury concentrations of 3400 ng/L (measured in 1997). 1500 g of mercury have been released from the mine each year.,
[Ganguli, Priya M., et al. "Mercury speciation in drainage from the New Idria mercury mine, California." Environmental science & technology 34.22 (2000): 4773-4779
]
Mercury Speciation in New Idria
Three main sources of mercury are industrial discharge,
atmospheric deposition, and discharge from inoperative gold and mercury mines. Idria, as well as the western United States as a whole, faces a sizable threat of
mercury contamination from the latter due to the prevalence of such mining operations.,
Mercury, known to be highly toxic, has been found in various forms in Idria:
elemental mercury (Hg(0)),
inorganic mercury (Hg(II)) and
monomethyl mercury(CH3Hg+, also called MMHg). MMHg, a potent
neurotoxin, poses the greatest threat to organisms.
Measurements were taken by collecting water samples, which were later analyzed by
tin chloride reduction,
atomic fluorescence, and
cold vapor atomic fluorescence spectrometry. The samples showed that mercury discharge and interaction was occurring throughout the course of the San Carlos Creek. The biggest contributions were found in the acid mine drainage and the mine tailings 1.2 km downstream from the drainage input.
[Ganguli, Priya M. Mercury speciation in acid mine drainage: New Idria Quicksilver Mine, California. Diss. UNIVERSITY OF CALIFORNIA, 1998]
However, mercury was not simply detected in steady increments; in some areas, there was mercury scavenging of unfiltered total mercury. Dissolved mercury also underwent
abiotic atmospheric evasion as gaseous mercury was released into the atmosphere. Both processes accounted for the loss of measured mercury concentrations downstream.
Effects and Consequences
New Idria utilized the process of
calcination
Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), gener ...
to mine
mercury, which involved crushing and roasting
cinnabar
Cinnabar (), or cinnabarite (), from the grc, κιννάβαρι (), is the bright scarlet to brick-red form of mercury(II) sulfide (HgS). It is the most common source ore for refining elemental mercury and is the historic source for the bri ...
, then condensing the release of mercury vapor.
The leftover
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
s or
calcines from this process were piled along with other waste rock, totaling between 0.5 and 2 million tons and cover over 40 acres of mining ground.
After the end of production in the 1970s,
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...
eventually flooded the mine and reacted with
high iron and
sulfur content of the bedrock. This created the ubiquitous
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
and
acidic solution in New Idria, which was contaminated and allowed to run into the San Carlos Creek. The issue was compounded by the proximity of 2,500 feet of the creek’s flow to the calcine tailing piles, contaminating the water with mercury and other metals including
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
,
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
,
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
, and
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
Although there are few regularly occupied developments near the mine, there is a significant ecological concern associated with the uncontrolled drainage.
A small concentration of mercury can harm aquatic organisms, poison water streams and surrounding
ecosystems
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
in highly contaminated areas like Idria.
Waters enriched in mercury were detected as far as 20 miles downstream from the mine in
Panoche Creek
Panoche Creek is a creek in San Benito and Fresno Counties, California, in the United States.
Historical names include Arroyo de Panoche Grande (Big Sugarloaf Creek)Mildred B. Hoover, et al. ''Historic Spots in California''. 3rd edition. Stanfo ...
, at levels toxic to aquatic life.
The lengths of San Carlos, Silver, and Panoche Creek run through a regionally unique wetland habitat housing several threatened and endangered species, including the California
red-legged frog and the
steelhead trout
Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and ...
. The river system eventually flows into the
San Joaquin River
The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
, and, subsequently,
San Francisco Bay, areas of both recreational and commercial fishing.
Cleanup
The proposal to add the
New Idria Mercury Mine to the
Environmental Protection Agency’s
Superfund List was made in March 2011. EPA worked to reroute the
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
out of the way of the waste pilings, construct a settling pool for the
AMD
Advanced Micro Devices, Inc. (AMD) is an American multinational semiconductor company based in Santa Clara, California, that develops computer processors and related technologies for business and consumer markets. While it initially manufactur ...
, and minimize the erosion of the pilings into San Carlos Creek. These actions were completed in November 2011, with follow-up investigations scheduled for late 2013.
See also
*
New Idria, California
*
Mercey Hot Springs, California
*
Panoche, California
*
San Joaquin River
The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
*
San Francisco Bay
*
California Gold Rush
*
List of Superfund sites in California
This is a list of Superfund sites in California designated under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) environmental law. The CERCLA federal law of 1980 authorized the United States Environmental Prote ...
References
External links
*
New Idria Mercury Mine Superfund site
{{San Benito County, California
Mining in California
Mercury mines in the United States
Mining communities in California
Asbestos mines
Diablo Range
Buildings and structures in San Benito County, California
California Historical Landmarks
History of San Benito County, California
Companies based in San Benito County, California
Superfund sites in California