In December 2010, EPA promulgated Federal Requirements Under the Underground Injection Control (UIC) for Carbon Dioxide Geologic Sequestration (GS) Wells (75 FR 77230, December 10, 2010), referred to in this UIC Quick Reference Guide as the GS Rule. The GS Rule establishes new federal requirements for the underground injection of carbon dioxide for the purpose of long-term storage, or geologic sequestration. While the elements of the final rule are based on the existing regulatory framework of EPA's UIC Program, the requirements are tailored to address the unique nature of CO(sub 2) injection for GS including: the relative buoyancy of carbon dioxide, its corrosivity in the presence of water, the potential presence of impurities in captured carbon dioxide, its mobility within subsurface formations, and large injection volumes anticipated at full scale deployment. The rule establishes a new well class (Class ) to ensure the protection of underground sources of drinking water (USDWs) from injection related activities. The Class VI requirements are also designed to promote transparency and national consistency in permitting of GS projects.