On July 15, 2008, the Environmental Protection Agency (EPA) proposed regulations under the Safe Drinking Water Act (SDWA) governing carbon sequestration, which is the long-term underground storage of carbon dioxide (CO2) emissions associated with power plant and industrial facility operations.1 Comments will be accepted for 120 days after the proposed rule is published in the Federal Register.

Underground sequestration involves taking CO2 or other greenhouse gas (GHG) emissions and depositing the material deep underground in stable geologic formations. The gasses are first captured, typically converted to a liquid state through compression, and then deposited underground using underground injection control (UIC) wells specifically designed and constructed for the task. The underground formations into which the materials are injected (including deep saline formations, unmineable coal seams, and depleted oil and gas fields) contain the sequestered material by both physical and geochemical processes. Low permeability “confining” layers physically prevent the buoyant CO2 from migrating upward. The material is also immobilized when the dissolved CO2 reacts with minerals in the injection formation. These physical and geochemical processes mimic the manner in which naturally-occurring CO2 is trapped in underground formations.

A well-established regulatory program to protect underground sources of drinking water already exists under the SDWA. The EPA currently regulates the underground injection of such things as industrial wastewater and even hazardous waste. The United States has abundant sources of underground formations for such injections. Certain properties of CO2, however, present specific challenges with respect to underground injection. Issues unique to the underground injection of CO2 include CO2’s buoyancy and its potential mobility in geologic formations, potential impurities in captured CO2, its corrosivity in water, and the large volumes of CO2 that potentially may be required to be captured and sequestered underground.

The proposed rule establishes a new class of UIC well (Class VI) for carbon sequestration wells. The EPA has proposed requirements that facilities wishing to install Class VI wells must, among other things:

  • Adequately characterize the proposed geologic injection formations and areas of review;
  • Insure that the UIC wells are constructed to resist corrosion and otherwise prevent fluid movement into unintended underground areas;
  • Operate the UIC wells pursuant to specific conditions; 
  • Monitor that the injected material is going to the intended injection zone; 
  • Periodically test the mechanical integrity of the UIC wells and monitoring equipment; 
  • Provide financial assurance mechanisms for proper well plugging, closure, site care, and emergency corrective action; and 
  • Obtain permits after providing opportunities for public comment and hearing.

The proposed rule also provides procedures for states that want to obtain primary authority over the Class VI UIC wells in their states.

The EPA has been gearing up for the proposed carbon sequestration rules for some time. In the past, Class II UIC wells have been used to inject CO2 for the purposes of enhanced oil recovery (EOR) and enhanced gas recovery (EGR). The EPA announced in October 2007 that the Agency planned to propose regulations to ensure consistency in permitting full-scale geologic sequestration projects in the summer of 2008. In March 2007, the EPA provided UIC Program Guidance to assist state and EPA regional UIC programs in processing permit applications for near-term geologic sequestration pilot projects prior to full-scale deployment using Class V experimental technology permits. Several such projects have been permitted, including projects in the Midwest.2 Since 2005, the EPA has held nine workshops on carbon sequestration around the country.

The proposed rule only governs CO2 once it is placed underground. The EPA specifically cautioned that the rule does not govern emissions of CO2 or any other greenhouse gas under the Clean Air Act.3 The rule also does not address the capture or transportation of CO2 to sites for sequestration. Carbon sequestration, according to the EPA, is one of a “portfolio of options” to address the impacts of GHG emissions, and the EPA wanted to make sure that the UIC program rules were updated to address the particular issues involved. In short, although no one will be required to sequester CO2 underground, the rule sets up the regulatory framework should anyone choose to do so.