SUCCESSIVE administrations have planned for it. The House and the Senate have approved it. The Energy Department is desperate to move forward on it. But the plan to create a permanent storage site for nuclear waste at Yucca Mountain in the Nevada desert may be delayed. The construction of the underground storage system, which may eventually cost up to $60 billion, was not fully funded in the president's budget this year, because the White House assumed Congress would pass legislation making a nuclear waste fund, which comes from user and utility fees, available to the project. That was one assumption too far: Congress failed to change the rules, and it has so far failed to find other ways to provide the funding needed to get the project on schedule.

This week, the U.S. Court of Appeals for the D.C. Circuit complicated matters further, handing down a unanimous decision dismissing most of the objections that figured in multiple lawsuits against Yucca Mountain, save one -- but it's a big one. The court concluded that the Environmental Protection Agency acted wrongly when its regulations governing construction of the site demanded only that it guarantee its safety for 10,000 years. In fact, the National Academy of Sciences -- whose views Congress has said the EPA must comply with in these matters -- has declared that geological concerns should be considered for a much longer period, even up to a million years. If Yucca Mountain is to comply with the law, the entire project must be rethought or redesigned with that in mind. Alternatively, the law has to be changed.

Theoretically, the latter course should be simplest. But this is an election year, and Nevada is a swing state whose voters definitely do not approve of nuclear waste in their back yard and whose legislators constantly work against it. Sen. John F. Kerry (D-Mass.) has stoked the political fires by denouncing the Yucca Mountain project, which the Bush administration supports. According to the Las Vegas Review-Journal, Mr. Kerry's vice presidential choice, Sen. John Edwards (D-N.C.), had promised within hours of his selection to defer to Mr. Kerry on the issue, despite having voted in favor of the nuclear waste repository in 2002. Chances seem slim that Congress will hold hearings on the design of the storage site or that it will pass legislation designed to sort some of this out -- the course of action the courts suggested.

Yet without a major show of political will, the project will never be built. We support the Yucca Mountain project on the grounds that the center of a desert mountain is a better place for the nation's nuclear waste than the several dozen current repositories, many of which are near cities and some of which already are unsafe. But no project of this scale can succeed if Congress is unable to maintain consistent support. Underfunding the research and the construction is one way to ensure an environmental disaster, either in Nevada or in one of the waste dumps that won't be cleaned up if Yucca Mountain isn't built. If politics prevents this project from attracting funding and proper attention, then Congress must propose another solution for the nation's nuclear waste.