The leak stage of the Deepwater Horizon catastrophe appears to be over, but it’s far too soon for the biggest oil spill in U.S. waters to retreat from the headlines.

Even though no oil is leaking from the deep-sea well the environmental costs of the cleanup will remain with us for years to come. So is the debate over how to better protect ourselves from something like this happening again.

A factor in both issues will be the environmental effect of chemical dispersants, which were used as never before in U.S. waters.

The chemicals seem to have worked. Although 16 times as much oil was spilled in the Gulf as was spilled in Alaska’s Prince William Sound by the Exxon Valdez, less than a quarter of the shoreline was contaminated with oil this time. But there are environmental trade-offs that will not be fully understood for some time.

Oil that would have been collected in a slick on the surface of the water, eventually washing up on shorelines and wetlands, broke up and sank below the surface, where some was eaten by microbes. But it also came into contact with underwater species, and no one knows the long-term effect it will have on fish, shrimp and other species. The safety of dispersants is a critical question when determining the future of offshore oil drilling.

A bill before the U.S. Senate is a modest effort to get ready for the next spill. In dispute is the size of a cap on liability for drill operators. A Republican version of the bill set the bar too low at $75 million. If that were in effect today, BP would have long met the maximum and American taxpayers would be financing cleanup efforts.

A stalled Democratic proposal calls for unlimited liability, which critics say would drive small companies out of business. A compromise that would set a $250 million ceiling on one company’s liability, with an industry-funded insurance policy covering costs beyond that appears to provide adequate protection for taxpayers.

These arguments do not resolve the central question of American energy policy and whether the United States should continue to chase low-cost petroleum or develop alternatives.

That discussion will have to wait for another day, but this oil spill reveals too many vulnerabilities for the nation to fail to act.