![Ralsko uran](https://upload.wikimedia.org/wikipedia/commons/f/fe/Ralsko_uran.JPG)
In-situ leaching (ISL), also called in-situ recovery (ISR) or solution mining, is a
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 via ...
process used to recover minerals such as
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 ...
and
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
through boreholes drilled into a deposit, ''
in situ
''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
''. In situ leach works by artificially dissolving minerals occurring naturally in a solid state. For recovery of material occurring naturally in solution, see:
Brine mining
Brine mining is the extraction of useful materials ( elements or compounds) which are naturally dissolved in brine. The brine may be seawater, other surface water, groundwater, or hyper-saline solutions from several industries (e.g., textile indu ...
.
The process initially involves the drilling of holes into the ore deposit. Explosive or pathways in the deposit for solution to penetrate. Leaching solution is pumped into the deposit where it makes contact with the ore. The solution bearing the dissolved ore content is then pumped to the surface and processed. This process allows the extraction of metals and salts from an
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 ...
body without the need for conventional
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 via ...
involving drill-and-blast, open-cut or
underground 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 via ...
.
Process
In-situ leach mining involves pumping of a
lixiviant A lixiviant is a chemical used in hydrometallurgy to extract particular elements from its ore. One of the most famous lixiviants is cyanide, which is used in extracting 90% of mined gold. The combination of cyanide and air converts gold particle ...
into the ore body via a borehole, which circulates through the porous
rock
Rock most often refers to:
* Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids
* Rock music, a genre of popular music
Rock or Rocks may also refer to:
Places United Kingdom
* Rock, Caerphilly, a location in Wales ...
dissolving the ore and is extracted via a second
borehole
A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petro ...
.
The lixiviant varies according to the ore deposit: for salt deposits the leachate can be fresh water into which salts can readily dissolve. For copper,
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
s are generally needed to enhance
solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solubil ...
of the ore minerals within the solution. For uranium ores, the lixiviant may be acid or
sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
.
Minerals
Potash and soluble salts
In-situ leach is widely used to extract deposits of water-soluble salts such as
potash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. (
sylvite and
carnallite
Carnallite (also carnalite) is an evaporite mineral, a hydrated potassium magnesium chloride with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare ...
),
rock salt (halite),
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
, and
sodium sulfate
Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates. All forms are white solids that are highly soluble in water. With an annual production of 6 milli ...
. It has been used in the US state of
Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
to extract
nahcolite
Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate ( Na H C O3) also called thermokalite. It crystallizes in the monoclinic system.
Nahcolite was first described in 1928 for an occurrence in ...
(
sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
). In-situ leaching is often used for deposits that are too deep, or beds that are too thin, for conventional
underground 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 via ...
.
Uranium
![NRC Uranium In Situ Leach](https://upload.wikimedia.org/wikipedia/commons/9/92/NRC_Uranium_In_Situ_Leach.png)
In-situ leach for uranium has expanded rapidly since the 1990s, and is now the predominant method for mining uranium, accounting for 45 percent of the uranium mined worldwide in 2012.
Solutions used to dissolve
uranium ore
Uranium ore deposits are economically recoverable concentrations of uranium within the Earth's crust. Uranium is one of the more common elements in the Earth's crust, being 40 times more common than silver and 500 times more common than gold. It ...
are either acid (
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
or less commonly
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
) or
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
(
sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
,
ammonium carbonate
Ammonium carbonate is a salt with the chemical formula (NH4)2CO3. Since it readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as smelling salt. It is also known as baker's ammonia and is ...
, or dissolved
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
). Dissolved oxygen is sometimes added to the water to mobilize the uranium. ISL of uranium ores started in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
and the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
in the early 1960s. The first uranium ISL in the US was in the
Shirley Basin
Shirley may refer to:
Arts and entertainment
* ''Shirley'' (novel), an 1849 novel by Charlotte Brontë
* ''Shirley'' (1922 film), a British silent film
* ''Shirley'' (2020 film), an American film
* ''Shirley'' (album), a 1961 album by Shirley Bas ...
in the state of
Wyoming
Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
, which operated from 1961-1970 using sulfuric acid. Since 1970, all commercial-scale ISL mines in the US have used
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
solutions.
ISL mining in Australia uses acid solutions.
![Ion exchange resin beads](https://upload.wikimedia.org/wikipedia/commons/0/08/Ion_exchange_resin_beads.jpg)
In-situ recovery involves the extraction of uranium-bearing water (grading as low as .05% U
3O
8). The extracted uranium solution is then filtered through resin beads. Through an ion exchange process, the resin beads attract uranium from the solution. Uranium loaded resins are then transported to a processing plant, where U
3O
8 is separated from the resin beads and
yellowcake
Yellowcake (also called urania) is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before f ...
is produced. The resin beads can then be returned to the ion exchange facility where they are reused.
At the end of 2008 there were four in-situ leaching uranium mines operating in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, operated by
Cameco
Cameco Corporation (formerly Canadian Mining and Energy Corporation) is the world's largest publicly traded uranium company, based in Saskatoon, Saskatchewan, Canada. In 2015, it was the world's second largest uranium producer, accounting for 18 ...
,
Mestena and Uranium Resources, Inc., all using sodium bicarbonate. ISL produces 90% of the uranium mined in the US. In 2010, Uranium Energy Corporation began in-situ leach operations at their Palangana project in
Duval County, Texas
Duval County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 9,831. The county seat is San Diego. The county was founded in 1858 and later organized in 1876. It is named for Burr H. Duval, a soldier in ...
. In July 2012
Cameco
Cameco Corporation (formerly Canadian Mining and Energy Corporation) is the world's largest publicly traded uranium company, based in Saskatoon, Saskatchewan, Canada. In 2015, it was the world's second largest uranium producer, accounting for 18 ...
delayed development of their Kintyre project, due to challenging project economics based on $45.00 U
3O
8. One ISR reclamation project was also in operation as of 2009.
Significant ISL mines are operating in
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
and
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. The Beverley uranium mine in Australia uses in-situ leaching. ISL mining accounted for 41% of the world's uranium production in 2010.
![LEUPowder](https://upload.wikimedia.org/wikipedia/commons/2/2f/LEUPowder.jpg)
Examples of in-situ uranium mines include:
* The
Beverley Uranium Mine
The Beverley Mine is Australia's third uranium mine and Australia's first operating in-situ recovery mine. It is located in South Australia in the gazetted locality of Wooltana about 35 km from Lake Frome at the northern end of the Flinder ...
, South Australia, is an operating ISL
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
mine and Australia's first such mine.
* The
Honeymoon Uranium Mine
The Honeymoon Mine was Australia's second operating in-situ recovery uranium mine, beginning production in 2011. It is located in South Australia and is northwest of Broken Hill, New South Wales.
Honeymoon is a sandstone-hosted paleochannel de ...
, South Australia, opened in 2011 and is Australia's second ISL uranium mine.
*
Crow Butte
Crow Butte is a uranium mining operation located southeast of the city of Crawford in Dawes County, Nebraska, United States. Cameco Corporation owns and operates Crow Butte through its wholly owned subsidiary, Crow Butte Resources, Inc.
Hist ...
(operating),
Smith Ranch-Highland (operating), Christensen Ranch (reclamation), Irigaray (reclamation), Churchrock (proposed), Crownpoint (proposed), Alta Mesa (operating), Hobson (standby), La Palangana (operating), Kingsville Dome (operating), Rosita (standby) and Vasquez (restoration) are ISL uranium operations in the United States.
* In 2010 Uranium Energy Corp. began an ISL mining operation in the Palangana deposit in
Duval County, Texas
Duval County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 9,831. The county seat is San Diego. The county was founded in 1858 and later organized in 1876. It is named for Burr H. Duval, a soldier in ...
. The ion exchange facility at Palangana trucks uranium-loaded resin beads to the company's
Hobson processing plant, where
yellowcake
Yellowcake (also called urania) is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before f ...
is produced. Uranium Energy Corp. has three additional South Texas deposits permitted or in development.
Rhenium
There are technologies for the associated extraction of
rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one ...
from productive solutions of underground leaching of uranium ores.
Copper
In-situ leaching of copper was done by the Chinese by 977 AD, and perhaps as early as 177 BC.
[ Copper is usually leached using acid (]sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
or hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
), then recovered from solution by solvent extraction electrowinning
Solvent extraction and electrowinning (SX/EW) is a two-stage hydrometallurgical process that first extracts and upgrades copper ions from low-grade leach solutions into a solvent containing a chemical that selectively reacts with and binds the co ...
(SX-EW) or by chemical precipitation.
Ores most amenable to leaching include the copper carbonates malachite
Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures ...
and azurite
Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the Type locality (geology), type locality at Chessy, Rhône, Chessy-les-Mines near ...
, the oxide tenorite
Tenorite is a copper oxide mineral with the chemical formula CuO.
Occurrence
Tenorite occurs in the weathered or oxidized zone associated with deeper primary copper sulfide orebodies. Tenorite commonly occurs with chrysocolla and the copper c ...
, and the silicate chrysocolla
Chrysocolla ( ) is a hydrated copper phyllosilicate mineral and mineraloid with formula (x<1)[ or .][
The structure of the mineral has been questioned, as a 2006 spectrographic study suggest material identified as ...]
. Other copper minerals, such as the oxide cuprite
Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper.
Its dark crystals with red internal reflections are in the isometric system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, ...
and the sulfide chalcocite
Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system.
The ...
may require addition of oxidizing agents such as ferric sulfate
Iron(III) sulfate (or ferric sulfate), is a family of inorganic compounds with the formula Fe2(SO4)3(H2O)n. A variety of hydrates are known, including the most commonly encountered form of "ferric sulfate". Solutions are used in dyeing as a morda ...
and oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
to the leachate before the minerals are dissolved. The ores with the highest sulfide contents, such as bornite
Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5 Fe S4 that crystallizes in the orthorhombic system (pseudo-cubic).
Appearance
Bornite has a brown to copper-red color on fresh surfaces that tarnishes to v ...
and chalcopyrite
Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mo ...
will require more oxidants and will dissolve more slowly. Sometimes oxidation is sped up by the bacteria ''Thiobacillus ferrooxidans
''Acidithiobacillus'' is a genus of the '' Acidithiobacillia'' in the "Pseudomonadota". The genus includes acidophilic organisms capable of iron and/or sulfur oxidation. Like all ''"Pseudomonadota"'', ''Acidithiobacillus'' spp. are Gram-negative. ...
'', which feeds on sulfide compounds.
Copper ISL is often done by ''stope leaching'', in which broken low-grade ore is leached in a current or former conventional underground mine. The leaching may take place in backfilled stopes or caved areas. In 1994, stope leaching of copper was reported at 16 mines in the US.
At the San Manuel Mine in the US state of Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, ISL was initially used by collecting the resultant solution underground but in 1995 this was converted to a well-to-well recovery method which was the first large scale implementation of that method. This well-to-well method has been proposed for other copper deposits in Arizona.
Gold
In-situ leaching has not been used on a commercial scale for gold mining. A three-year pilot program was undertaken in the 1970s to in-situ leach gold ore at the Ajax mine in the Cripple Creek district in the US, using a chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
and iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
solution. After obtaining poor results, perhaps because of the complex telluride ore, the test was halted.
Environmental concerns
According to the World Nuclear Organization:
In the USA legislation requires that the water quality in the effected aquifer be restored so as to enable its pre-mining use. Usually this is potable water or stock water (usually less than 500 ppm total dissolved solids), and while not all chemical characteristics can be returned to those pre-mining, the water must be usable for the same purposes as before. Often it needs to be treated by reverse osmosis, giving rise to a problem in disposing of the concentrated brine stream from this.
The usual radiation safeguards are applied at an ISL Uranium mining operation, despite the fact that most of the orebody's radioactivity remains well underground and there is hence minimal increase in radon release and no ore dust. Employees are monitored for alpha radiation contamination and personal dosimeters are worn to measure exposure to gamma radiation. Routine monitoring of air, dust and surface contamination are undertaken.
The advantages of this technology are:
*Reduced hazards for the employees from accidents, dust, and radiation,
*Low cost, no need for large uranium mill tailings deposits.
After termination of an in-situ leaching operation, the waste slurries produced must be safely disposed, and the aquifer, contaminated from the leaching activities, must be restored. Groundwater restoration is a very tedious process that is not yet fully understood.
The best results have been obtained with the following treatment scheme, consisting of a series of different steps:
*Phase 1: Pumping of contaminated water: the injection of the leaching solution is stopped and the contaminated liquid is pumped from the leaching zone. Subsequently, clean groundwater flows in from outside of the leaching zone.
*Phase 2: as 1, but with treatment of the pumped liquid (by reverse osmosis) and re-injection into the former leaching zone. This scheme results in circulation of the liquid.
*Phase 3: as 2, with the addition of a reducing chemical (for example hydrogen sulfide (H2S) or sodium sulfide (Na2S). This causes the chemical precipitation and thus immobilization of major contaminants.
*Phase 4: Circulation of the liquid by pumping and re- injection, to obtain uniform conditions in the whole former leaching zone.
But, even with this treatment scheme, various problems remain unresolved:
*Contaminants that are mobile under chemically reducing conditions, such as radium, cannot be controlled.
*If chemically reducing conditions are later disturbed for any reasons, the precipitated contaminants are re-mobilized.
*The restoration process takes very long periods of time, not all parameters can be lowered appropriately.
Most restoration experiments reported refer to the alkaline leaching scheme, since this scheme is the only one used in Western world commercial in-situ operations. Therefore, nearly no experience exists with groundwater restoration after acid in- situ leaching, the scheme that was applied in most instances in Eastern Europe. The only Western in-situ leaching site restored after sulfuric acid leaching so far, is the small pilot scale facility Nine Mile Lake near Casper, Wyoming (USA). The results can therefore not simply be transferred to production scale facilities. The restoration scheme applied included the first two steps mentioned above. It turned out that a water volume of more than 20 times the pore volume of the leaching zone had to be pumped, and still several parameters did not reach background levels. Moreover, the restoration required about the same time as used for the leaching period.
In USA, the Pawnee, Lamprecht, and Zamzow ISL Sites in Texas were restored using steps 1 and 2 of the above listed treatment scheme.
Relaxed groundwater restoration standards have been granted at these and other sites, since the restoration criteria could not be met.
A study published by the U.S. Geological Survey in 2009 found that "To date, no remediation of an ISR operation in the United States has successfully returned the aquifer to baseline conditions."
Baseline conditions include commercial quantities of radioactive U3O8. Efficient in-situ recovery reduces U3O8 values of the aquifer. Speaking at an EPA
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 be ...
Region 8 workshop, on September 29, 2010, Ardyth Simmons, PhD, Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
(Los Alamos, NM
Los Alamos is an census-designated place in Los Alamos County, New Mexico, United States, that is recognized as the development and creation place of the atomic bomb—the primary objective of the Manhattan Project by Los Alamos National Labora ...
) on the subject "Establishing Baseline and Comparison to Restoration Values at Uranium In-Situ Recovery Sites" stated "These results indicated that it may be unrealistic for ISR operations to restore aquifers to the mean, because in some cases, this means that there would have to be less uranium present than there was pre-mining. Pursuing more conservative concentrations results in a considerable amount of water usage, and many of these aquifers were not suitable for drinking water before mining initiated."
The EPA is considering the need to update the environmental protection standards for uranium mining because current regulations, promulgated in response to the Uranium Mill Tailings Radiation Control Act of 1978, do not address the relatively recent process of in-situ leaching (ISL) of uranium from underground ore bodies. In a February, 2012 letter the EPA states, "Because the ISL process affects groundwater quality, the EPA’s Office of Radiation and Indoor Air requested advice from the Science Advisory Board (SAB) on issues related to design and implementation of groundwater monitoring at ISL mining sites."
The SAB makes recommendations concerning monitoring to characterize baseline groundwater quality prior to the start of mining operations, monitoring to detect any leachate excursions during mining, and monitoring to determine when groundwater quality has stabilized after mining operations have been completed. The SAB also reviews the advantages and disadvantages of alternative statistical techniques to determine whether post-operational groundwater quality has returned to near pre-mining conditions and whether mine operation can be predicted not to adversely impact groundwater quality after site closure acceptance.
See also
* Heap leaching
Heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and re-separate them after their division from other e ...
* Hydraulic fracturing
Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "frack ...
* Mineral exploration
Mining in the engineering discipline is the extraction of minerals from underneath, open pit, above or on the ground. Mining engineering is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, and ...
References
External links
Heathgate Resources Acid Leach Infopage
{{DEFAULTSORT:In-Situ Leach
Mining techniques
Economic geology
Uranium
Solution mining