In-situ Leach Uranium Mining
First used in Wyoming in the 1950s, in-situ leaching (ISL) mining accounts for most uranium production in the United States.
ISL involves injecting chemicals, called “lixivants” into an aquifer that contains a uranium ore body (i.e. deposit). The chemicals used are typically sulfuric acid or ammonium carbonate.
Under natural conditions, these ore bodies are localized and the radiation and heavy metals associated with them remain confined in small portions of an aquifer. Because under natural conditions the toxic substances associated with uranium ore bodies are locally confined, their host aquifers can be – and often are – used as drinking water sources.
When lixiviant is injected into an aquifer, it creates a chemical reaction with the uranium, causing it to spread over large areas of an aquifer. The uranium plume is brought to the surface with a series of “production wells” and processed for shipment to enrichment facilities.
In the US the production life of a well field is roughly 1 to 3 years 1. However, groundwater restoration efforts can last for decades.
In situ recovery process.
Image: Nuclear Regulatory Commission
ISL operations are permitted and regulated by the Nuclear Regulatory Commission (NRC) or through agreement with states.
The NRC currently regulates ISL operations in Wyoming, Nebraska, and New Mexico.
In all cases, ISL uranium mines must obtain -
- an aquifer “exemption” permit to degrade the quality of groundwater resources, and
- an underground injection control permit from a state regulatory agency or the EPA in order to pollute the groundwater during the mining operation.
Exempted aquifers are exempted from the Safe Drinking Water Act and cannot be used as a future underground source of drinking water.
Regulation of ISL operations has proven problematic.
The primary problem with ISL regulation: the NRC acknowledges that, although ISL permits require complete restoration of groundwater conditions after mining operations, some of the “baseline parameters” have proved to be unachievable by mining companies.
While the uranium mining industry insists that ISL mining methods are environmentally safe, numerous fines and violations by regulatory agencies have shown just how problematic ISL operations can be.
The increase in ISL environmental violations in recent years has led many states to relax environmental standards rather than impose stricter regulations against the mining companies.
Of the 8 currently operating ISL operations in the United States, only one has not had any reported environmental violations (Alta Mesa, Texas). Most ISL projects have had numerous spills, contaminated underground aquifers, and have failed to reclaim non-operating on site wells.
For more information:
- Earthworks: In Situ Leach Uranium Mining. Fact sheet.
- Casper Star-Tribune: In-situ leach process drives Wyoming uranium ambitions, September 30, 2010.
- Energy Information Administration: Domestic Uranium Production Report - Quarterly
- Nuclear Regulatory Commission: In Situ Recovery Facilities
- WISE Uranium Project: Impacts of Uranium In-Situ Leaching