Once CO2 reaches a freshwater aquifer, the quality of the drinking water is site specific, and depends on an array of factors including the size of the leak and the types of bacteria in the water, Little said. “By no means would all sites be susceptible to problems of water quality,” Jackson added.
Other researchers are trying to determine how a very large leak might affect the subsurface environment, while the Department of Energy (DOE) and private investors are beginning studies of potential groundwater contamination in the field, rather than in a lab as Jackson and Little did.
The paper was published just as EPA finished from contamination following a CO2 leak. Announced on November 22, the rule is written for the owners and operators of potential CCS wells. It’s designed to ensure that the wells are appropriately sited, constructed, tested, monitored, and closed, according to EPA.
Sally Benson, director of the Global Climate and Energy Project at Stanford University, said EPA’s rule should protect groundwater because it will make it difficult to inject CO2 too close to a possible drinking water source. She also said the new study doesn’t present any surprises and is not likely to put an obstacle in the way of those CCS projects in the planning stages.
“Really, it gets down to making sure projects are designed carefully and that the project has monitoring so that one has early warning of any CO2 movements,” Benson added.
But drinking water utilities aren’t convinced that EPA’s rule will protect water sources from metal contamination resulting from the bubbling up of CO2, which is sure to occur in small amounts at least.
Cynthia Lane with the American Water Works Association (AWWA), a nonprofit research and advocacy organization representing researchers and water utilities, said this rule doesn’t include specific site selection criteria. Rather, the rule leaves many of the decisions about site selection and permit approval up to each state.
“It is not as protective as we might like,” said Lane. “We are concerned about the quality of drinking water. There is a definite shift in certain parts of country to use saline or more brackish water for drinking.”
Groundwater protections should be in place for areas in the southwest, such as Las Vegas, where utilities are having a difficult time finding water sources, Lane said. “They are using anything that is wet no matter what the saline content is,” Lane added.
After observing the CO2 percolating through aquifer sand and sediment for a year, Jackson said the study strongly suggests to him that long-term monitoring for CO2 leakage into freshwater aquifers should be part of every CCS project.
The CO2 caused concentrations of manganese, cobalt, nickel, and iron to increase by more than 100 times the original levels (or 2 orders of magnitude), and potentially dangerous uranium and barium increased throughout the entire experiment in some samples. In general, they found that iron and manganese concentrations increased within 100 days. The response of other potentially harmful metals was more varied.
“We don’t want a private homeowner with a well that is not regularly monitored by the local utility to suddenly have elements in their groundwater that they don’t even know about.”
The two researchers are now collecting data on sites that are under consideration by DOE and private consortiums.
“Our next step is to do incubations under a variety of conditions,” said Jackson. “I think we could contribute to a list that indicates why certain sites are better than other sites.”
Photo: Artur Jan Fijałkowski