Storing large volumes of carbon dioxide from coal and other fossil fuels underground to reduce greenhouse gas emissions cannot be at the expense of the nation\u2019s drinking water supply, lawmakers said at a Congressional hearing July 24. Committee members pointed to the serious groundwater contamination from MTBE, particularly in California, after it was added to gasoline to reduce air pollutants. The House Committee on Energy and Commerce\u2019s Subcommittee on Environment and Hazardous Materials conducted the hearing on the Environmental Protection Agency\u2019s proposed regulations for carbon capture and sequestration, a technology that is not commercially viable. Representative Doris Matsui (D-CA) noted that 50 percent of California\u2019s population depends on groundwater. \u201cIt is really California\u2019s gold,\u201d she said. A number of states have imposed restrictions on coal-fired power plants because of their inability to capture and sequester carbon dioxide, said Rep. John Shadegg (R-AZ). \u201cIt would be a grave error for us to move forward with technologies that trade one environmental problem of carbon dioxide in the air with contamination of groundwater from carbon sequestration,\u201d he warned. Committee members expressed concern that the proposed regulations that EPA administrator Stephen Johnson signed July 15 would let those involved in sequestering and storing carbon off the hook for polluting groundwater wells and aquifers. The proposed rule promulgated under the Safe Drinking Water Act would place a 50-year limit on liability after injecting carbon underground. It also would not hold polluters liable for remediation under the federal Superfund and Resource Conservation and Recovery Acts. The EPA\u2019s proposed rulemaking focuses on technical requirements and does not address liabilities under federal statutes, said Benjamin Grumbles, assistant administrator for the EPA\u2019s Office of Water. Injection of large volumes of carbon dioxide at high pressures could contaminate groundwater aquifers with saline, sulfur, mercury, and other pollutants, warned Subcommittee chairman Gene Green (D-TX). Carbon dioxide injection could be hazardous if located near active fault lines, which could release large amounts of carbon dioxide if an earthquake occurred. The EPA regulations would require carbon dioxide to be sequestered in deep and stable geologic formations at least one-half mile underground below most groundwater aquifers and containing multiple barriers to migration, Grumbles said. The critical factor in trapping carbon underground and preventing migration is encasing it in a seal, or shale rock that is impermeable to the flow of fluids, according to Robert Burruss, a research geologist with the U.S. Geological Survey. Burruss and other geologists envision injecting CO2 in substrates below 3,000 feet and physically trapping it in saline formations with an overhead rock barrier to prevent migration or groundwater contamination. Geologists are studying large volumes of naturally-occurring underground carbon from oil and gas formations to understand how to trap and contain carbon underground. There are also many places in the world, such as volcanoes, where natural CO2 vents and leaks are hazardous. The Department of Energy is responsible for overseeing development of carbon capture and sequestration technology and has funded seven regional partnerships, said Scott Klara, director of the DOE\u2019s Strategic Center for Coal. The DOE is developing a map and comprehensive data base of potential sites. The agency recently discontinued funding for the $1 billion Future Gen sequestration project because of unresolved technology problems and cost overruns. The agency also is studying the technology of carbon injection to enhance oil recovery. Currently 35 million tons a year of CO2 is injected for enhanced oil recovery compared to 8 million tons of CO2 a year emitted by a large power plant, he said. In the future, natural gas-fired power plants also will be candidates for carbon sequestration in states like California, he said.