State and congressional leaders must push harder for the U.S. Department of Energy to clean up toxic wastes at the Savannah River Site.

A key processing plant to help get that done is almost four years behind schedule and hundreds of millions of dollars over budget.

But the Department of Energy and Congress cannot quit now.

Even though the salt-waste processing plant is only 65 percent complete and might not open until 2018, it must remain a top priority at the 310- square-mile federal nuclear weapons complex near Aiken. The plant is needed to clean up 47 tanks filled with highlevel nuclear waste. The aging tanks are prone to leaks.

Even if the plant’s cost — originally estimated at $400 million — goes higher than current estimate of $1.3 billion, so be it. It offers a concrete solution to a dire problem, and when it comes to cleaning up the atomic waste of America’s Cold War, few alternatives offer such hope.

Cost-overruns are not nearly as catastrophic as other bad news on nuclear waste disposal.

It was much worse when President Barack Obama foolishly terminated the proposed Yucca Mountain repository for nuclear waste nationwide. It also is worse to hear the Savannah River site mentioned as a possible place to store highly radioactive spent nuclear fuel from the nation’s nuclear reactors.

Cost overruns and delayed delivery are commonplace in the long slog that has turned into the nation’s greatest environmental challenge: storing nuclear waste and cleaning up sites like the Savannah River Site.

It is not quick, and it is not cheap. And Congress must stay the course.

The federal government created the dangerous situation at the Savannah River site, and it cannot be allowed to falter in cleaning up the mess.

— The Island Packet of Hilton Head (S.C.)