Office of
United States	Ground Water and
Environmental Protection Agency	Drinking Water
What is a solution mining well?	Solution mining wells are used to extract desired minerals from mines that have already been
conventionally mined. Leaching solutions (called "lixiviants") are injected through solution
mining wells into an underground ore deposit, metals are leached from the ore, and the
resulting "pregnant" solution is pumped to the surface for subsequent recovery from the
solution. Wells used to inject lixiviant into ore bodies that have not been conventionally
mined beforehand are considered Class III solution mining wells, not Class V.
What types of fluids are injected	The characteristics of the injected solution are highly dependent on those of the ore body
into solution mining wells?	being mined because a variety of metals present in the ore are incorporated into the solution
as it goes through repeated cycles of injection, extraction, and reinjection.
Do injectate constituents exceed	Available data on the composition of solution mining fluids indicate that the concentrations
drinking water standards at the	of sulfate, molybdenum, radium selenium, arsenic, lead, and uranium exceed primary
point of injection?	drinking water standards and health advisory levels. Concentrations of total dissolved
solids, chloride, manganese, aluminum, iron, sulfate, and zinc have been measured above the
secondary drinking water standards.
In many cases, the hydrogeology of the injection zone, or mined ore body, has already been
altered by ground water pumping as well as previous mining. In uranium mining, for
example, the formation is a water-bearing sandstone. As part of solution mining operations,
ground water flow is normally modified to create a drawdown, or zone of depression, so that
the injected lixiviant is retained in the leaching zone for subsequent recovery.
No ground water contamination incidents have been identified that are directly attributable
to Class V solution mining injection wells. However, the fluids injected into these wells
inherently contain a variety of metals at concentrations above drinking water standards or
health advisory levels, and contamination resulting from a combination of mining-related
activities has been reported at several sites. Elevated concentrations of metals have been
observed in ground water in the vicinity of solution mining operations, but complex
hydrogeology and other mining and mining-related activities make it difficult to attribute the
cause to a specific activity, such as solution mining injection wells.
Are solution mining wells
No information was collected that indicates these wells are vulnerable to receive spills or
vulnerable to spills or illicit
illicit discharges.

How many solution mining wells
There are 2,694 documented solution mining wells in the United States.
exist in the United States?

Where are solution mining wells
Eight of the documented solution mining wells are associated with a uranium mine in NM;
located within the United States?
the remaining wells occur at two copper mines in AZ.
How are solution mining wells
Individual permit. AZ, NM
regulated in states with the largest

number of this type of well?

Where can I obtain additional	For general information, contact the Safe Drinking Water Hotline, toll-free 800-426-4791.
information on solution mining	The Safe Drinking Water Hotline is open Monday through Friday, excluding federal
wells?	holidays, from 9:00 a.m. to 5:30 p.m. Eastern Standard Time. For technical inquiries,
contact Amber Moreen, Underground Injection Control Program, Office of Ground Water
and Drinking Water (mail code 4606), EPA, 401 M Street, SW, Washington, D.C., 20460.
Phone: 202-260-4891. E-mail: mo re e n. a mb e r Vv c pa. go v. The complete Class VUIC Study
(EPA/816-R-99-014, September 1999), which includes a volume addressing solution mining
wells (Volume 12), can be found at http://www.epa.gov/OGWDW/uic/cl5study.html.
What are the characteristics of the
injection zone of a solution mining
Are there any contamination
incidents associated with solution
mining wells?