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Water: Class VI Injection Wells

Geologic Sequestration Class VI Wells

What is a Class VI Well?

Class VI wells are wells used for injection of carbon dioxide (CO2) into underground subsurface rock formations for long-term storage, or geologic sequestration. Geologic sequestration refers to a suite of technologies that may be deployed to reduce CO2 emissions to the atmosphere to help mitigate climate change. (For information about geologic sequestration and climate change, see EPA's Geologic Sequestration and Climate Change pages)

How do Class VI wells protect drinking water resources?GS Class VI well

 Class VI well requirements are designed to ensure that wells are sited, constructed, operated, tested, monitored, and closed in a manner that is protective of underground sources of drinking water (USDWs). The regulations are based on the existing Underground Injection Control (UIC) Program regulatory framework with modifications to address the unique nature of CO2 injection for GS, including: the relative buoyancy of CO2, its mobility in the subsurface, its corrosivity in the presence of water, and the large injection volumes anticipated at GS projects.

What are the requirements for Class VI wells?

EPA developed specific criteria for Class VI wells:

  • Extensive site characterization requirements

  • Well construction using materials that are compatible with and can withstand contact with CO2 over the life of the GS project

  • Comprehensive monitoring of all aspects of well integrity, CO2 injection and storage, and groundwater quality during the injection operation and the post-injection site care period

  • Wells Financial responsibility requirements to assure the availability of funds for the life (including post-injection site care and emergency response) of the GS project.


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