The Environmental Protection Agency wants to make sure curbing global warming doesn't contaminate drinking water.
In its first regulations on the burial of carbon dioxide underground, the EPA on Tuesday unveiled measures to protect drinking water from the gas behind the bubbles in carbonated beverages. The fledgling technology, known as carbon sequestration, is critical to reducing carbon dioxide released into the air from coal-fired power plants.
"This rule paves the way for technologies that will protect public health and reduce the effects of climate change," said Benjamin Grumbles, an assistant administrator in the agency's water office.
The proposal upgrades the 1974 Safe Drinking Water Act to include a new category of injection wells solely for carbon dioxide storage, and creates extensive siting, testing and monitoring requirements to prevent leaks. The EPA already regulates injection wells used to boost oil production and dispose of hazardous and non-hazardous waste.
While carbon dioxide in water itself isn't a problem _ think Perrier or Diet Coke _ too much of the benign bubbles can turn water slightly acidic, and leach toxic heavy metals and other contaminants out of the surrounding rock and into water supplies. Injecting carbon dioxide underground can also push other pollutants, such as saltwater, into underground aquifers.
"The risks are small, but if sequestration was to be used very widely, a small risk becomes large," said Susan Hovorka, a scientist with the Bureau of Economic Geology at the University of Texas in Austin who has done research on long-term storage of carbon dioxide.
The United States has the capacity to store 3,900 gigatons of carbon dioxide at 230 different underground storage sites, according to Energy Department estimates. The U.S. emits a total of about seven gigatons of carbon dioxide every year.
To date, the bulk of carbon dioxide being injected underground has been done to enhance oil production. But if coal-fired power plants, as expected, start to embrace carbon sequestration technology, more of the carbon dioxide belched out of smokestacks is expected to be entombed in microscopic spaces in underground rock.
A final rule is expected in late 2010 or 2011, the EPA said. The House Energy and Commerce Committee will hold a hearing next week to look at the environmental effects of sequestration.