I just participated in an EPA webcast, and it appears that although the carbon sequestration rule will be proposed under SDWA, it's EPA's attempt at a climate change mitigation strategy in its water programs. It's not so surprising that it would be introduced under the SDWA - the underground injection control regs are in the water bureau, and EPA says that the main reason its under SDWA is to make sure drinking water is protected with the GHG strategy of sequestration. EPA says to expect the publishing of the proposed rulemaking in July 2008.

I don't know if it matters where it's proposed, as long as people are asking the right questions about the dangers and benefits of the strategy. Just because carbon has been stored underground naturally for millions of years doesn't mean that it necessarily follows that so much should be stored there unnaturally. We'll see when the rule comes out I guess.

To perform carbon sequestration, carbon gas needs to be liquefied through compression.  That’s a costly and energy-intensive process.  The liquid then needs to be transported to the right geological formation.  Some people believe the best approach is to just build the power plant right near the spot where injection can occur.  But that doesn’t account for the thousands of existing plants that are nowhere near potential wells.  Trucking or piping liquefied carbon has its own environmental and economic drawbacks.  In any case, injecting carbon deep enough so it doesn’t even pose a risk to ground water or other ecosystems (ocean-bed injection is one high-risk ecological scenario) is an excruciatingly complex, expensive, and uncertain proposition when one considers the number of U.S. fossil fuel power plants.   In my opinion, carbon sequestration as an approach to climate change falls far behind renewable energy and nuclear power.