The military's challenge of handling the munitions discarded off O'ahu's shores is a terrible mess, but one that neatly illustrates the repercussions of a careless act.

More than six decades ago, enormous quantities of chemical munitions were stowed in deep water, in two spots five and 10 miles off Pearl Harbor and in one about 10 miles off the Leeward Coast.

At around the same time, a load of conventional weapons was dumped in shallower reef waters closer to the Wai'anae shoreline. A smattering of flammable pellets, which may have been associated with this cache, has in recent months washed up on the beach.

The dumping happened during a time of war, in an era of environmental indifference, so those acts can't be evaluated by modern standards of behavior. But that indulgence still doesn't erase the fact that we now realize the harm and now must do something about it.

The good news is that the Department of Defense seems to be going about righting the wrong in a responsible and responsive way, consulting with federal and local authorities and — most importantly — keeping communication lines open between decisionmakers in Washington, D.C., and the Isle communities most affected.

Naturally, Hawai'i isn't alone. Five years ago, Congress required Defense to compile a list of all munitions-contaminated sites in the country. Thousands of acres are involved nationally, and the funding pipeline for some of the cleanup projects in other parts of the country hasn't always flowed smoothly.

That's why the community must remain engaged with the military on this project to see that Hawai'i benefits from as thorough a cleanup as possible. Sampling and exploration at the deep-water sites should begin on schedule this fall, and officials hope studies of the near-shore reef location will begin soon, as well.

The work is slow and deliberate by necessity, but congressional delegates need to keep tabs on Hawai'i's share of the funding.

Nobody knows exactly what harm would come from failing to clean up the sites, but that's not a gamble today's leaders should take. Risking future safety and environmental quality is not an option.