One of the many strategies being considered for combating climate change is to capture carbon dioxide emissions and bury them below the surface. Commonly known as carbon sequestration, this process has yet to be proven on a large scale as a viable remedy, though it has been studied for decades, and is routinely used on a smaller scale as part of operations such as oil and gas drilling.
EPA has been working on regulations designed to protect drinking water from this type of underground injection process, and on July 25, 2008, published a proposed rule. For information related to that rule, and work prior to and after it, see:
The public comment period closed Dec. 24, 2008.
But new data that has surfaced since the proposed rule was published has spurred the agency to open a short new public comment period. The new information comes from test projects around the country and the world, and research by the Lawrence Berkeley National Laboratory.
- DoE, Lawrence Berkeley Lab Research Projects: CO2 Geological Storage & Groundwater Resources  (includes extensive information on the sequestration process, specific studies, names of researchers, and publications) .
- DoE, Carbon Sequestration Regional Partnerships  (which support various test projects).
- Federal Register notice for new comment period  (EPA-HQ-OW-2008-0390).
EPA had been planning to issue a final rule some time in 2010, but the timing now depends in part on feedback on this new information. In addition, the agency is contemplating whether it needs more comprehensive regulations to address growing concerns beyond risks to drinking water.
Among the potential concerns are intrusion of CO2, as well as other contaminants that could be injected with the CO2, into water supplies and surrounding rocks that could alter acidity and possibly increase toxicity of the water by affecting underground metals, solvents, and other substances (a plausible outcome for contaminants such as arsenic, barium, lead, and zinc, according to Lawrence Berkeley Lab studies).
Another concern is the potential effect the injected volumes will have on moving or displacing existing subsurface waters and brines, potentially causing harmful ripple effects. A third potential concern is land uplift caused by the injected substances (which is the counterpart of land subsidence that occur at times when water, oil, or gas are extracted). A fourth issue is pressurization of the subsurface that could cause unpredictable geological changes. One of the new studies has confirmed that pressure changes could occur at least 250 miles away.
Any of these adverse effects could occur in vastly different ways in settings very close to each other, depending on the exact nature of the local geology.
The new 45-day public comment period will last until Oct. 15, 2009. As part of this process, there will be a public hearing Sept. 17, 2009, from 9 a.m. to 4 p.m., at the EPA Region 5 office in Chicago,  77 West Jackson Blvd., Lake Michigan Room (12th Floor). Contact is Sean Porse,  202-564-5990.
In addition to the agencies and researchers involved, others with an interest in this topic include various environmental groups. One source for identifying prospects is SEJ's "Climate Change" page. 
To get viewpoints from major CO2 sources such as coal-fired power plants, try your local utility or its parent organization, such as American Electric Power, Southern Company, Duke Energy, the Tennessee Valley Authority, Xcel Energy, or Pacific Gas and Electric. You can also try an umbrella group such as the Edison Electric Institute.
Another type of industry source is local gas, oil, coal, and salt companies that may be proposing that their tapped fields or excavated caverns be used as reservoirs for the CO2. Check with your local companies, or organizations such as the American Petroleum Institute, the American Gas Association, or the Salt Institute.
Local water utilities, state drinking-water regulatory agencies, or other agencies or users concerned about groundwater, including farmers, are another obvious source.
You can also check on specific exploratory and test carbon sequestration projects in many parts of the country. The Dept. of Energy's Regional Partnerships noted above cover almost the entire country, and are working on various aspects of the issue from a regional perspective. A primary task is to implement nine major demonstration projects to test the feasibility of — and mitigation measures necessary for — carbon sequestration in different circumstances in the US and Canada.
One of the projects under way involves a field test of CO2 injection in a Marshall County, WV, coal seam. The test, expected to last more than two years, involves both CO2 sequestration and coalbed methane recovery.
- DoE: press release of Sept. 8, 2009. 
In Hopkins County, KY, fieldwork has begun with injection of CO2 into an old oil field. This test is tied to effects on oil recovery. This project will also last more than two years.
- DoE: press release of June 25, 2009. 
One of the results of research near Shadyside, Ohio, has been a number of surprises regarding the local geology's physical response, with one outcome being unexpected pressure changes in the formation.
- DoE: press release of May 20, 2009. 
In Decatur, IL, work is under way in conjunction with an ethanol facility, which will dump its CO2 emissions into the underlying sandstone formation. That process is expected to last about three years.
- DoE: press release of April 6, 2009.