RICHLAND, Wash. — A stainless steel tank the size of a basketball court lies buried in the sandy soil of southeastern Washington state, an aging remnant of U.S. efforts to win World War II. The tank holds enough radioactive waste to fill an Olympic-sized swimming pool. And it is leaking.

For 42 years, tank AY-102 has stored some of the deadliest material at one of the most environmentally contaminated places in the country: the Hanford Nuclear Reservation. This complex along the Columbia River holds a storied place in American history. It was here that workers produced the plutonium for the atomic bomb dropped by the U.S. on Nagasaki, Japan, in 1945 — effectively ending the second world war.

Today Hanford’s legacy is less about what was made here than the environmental mess left behind — and the federal government’s inability, for nearly a quarter-century now, to rid Hanford once and for all of its worst hazard: 56 million gallons of toxic waste cached in aging underground tanks.

Technical problems, mismanagement and repeated delays have plagued the interminable cleanup of the 586-square-mile site, prolonging an effort that has cost taxpayers $36 billion to date and is estimated will cost $115 billion more.

Add to that the leaks involving AY-102 and other tanks at the site, and watchdog groups, politicians and others are left wondering: Will Hanford ever really be free of its waste? If not, what will its environmental impact be on important waterways, towns and generations to come?

“One corner of our country and my state acted as a stalwart during World War II and the Cold War and did the right thing,” Washington Gov. Jay Inslee said in a recent interview. “We want the federal government to fulfill its obligation to our state.”

There is no greater challenge at Hanford today than its underground tank waste. The leaks inside AY-102, a double-walled tank that was supposed to provide more protection against spillage — as well as newer leaks found this year in six other single-walled tanks — show how critical the situation has become.

Put simply: Time is running out on Hanford’s deteriorating tanks and, in turn, for completing work on a more permanent solution to store what’s in them.

The federal government created Hanford at the height of World War II, moving 50,000 people to sagebrush fields, dotted with small farms, near the Washington-Oregon border for a top-secret construction project. The influx quickly made this area Washington’s fourth-largest city, but most workers didn’t even know exactly what they were building — the world’s first full-scale nuclear reactor — until the bomb was dropped on Nagasaki.

In ensuing years, workers built eight more reactors to produce plutonium for the nation’s nuclear weapons arsenal. They also built hundreds of ancillary projects, including large canyons where toxic chemicals were used to reprocess the plutonium and extract uranium.

All of this work produced massive amounts of radioactive and toxic waste, as reprocessing of the spent nuclear fuel created byproducts that were far too dangerous for human contact. Workers poured some of that waste directly into trenches in the ground at Hanford, but most of the deadliest waste was stored in 177 underground tanks, grouped into areas known as tank farms.

There isn’t much to see at these tank farms. Gravel fields cover the tanks themselves. Exhaust pipes jut out of the ground above each of them. Underground, they hold a bubbling, brewing stew of radionuclides, hazardous chemicals and nitrates. Two radionuclides comprise much of the radioactivity: cesium-137 and strontium-90. Both take hundreds of years to decay, and exposure to either would increase a person’s risk of developing cancer.

The first storage tanks, 149 of them, were built between 1943 and 1964 with just a single, stainless-steel wall. They were designed to last only 10 to 20 years, because they were intended as a stopgap measure until a more permanent solution could be found to deal with the waste. It turned out the tanks were susceptible to corrosion; some even buckled from the extreme heat radiated by the waste.

As early as 1956, workers suspected one tank was leaking. Between 1959 and 1968, the U.S. Energy Department confirmed that 12 tanks were leaking.

Around that time, workers started building 28 double-walled tanks to provide better protection, then began pumping the most dangerous liquid waste out of the leaking tanks into these vessels. By 1995, they had gotten as much of the liquid out as possible, leaving behind sludge the consistency of peanut butter.

AY-102 was the first double-walled tank, put into service in 1971 with an intended lifespan of 40 years. The tank contains chunks of solids — many common metals, including aluminum, nickel, lead, silver, copper, titanium and zinc — as well as other common elements. It also holds more than a dozen radionuclides, such as plutonium, uranium, strontium and cesium, all of which can cause cancers upon contact.

Last fall, at 41 years of age, AY-102 was found to be leaking into the space between its inner and outer shells. So far, no waste has escaped the outer shell to the soil surrounding the tank, and a video review of six other double-shell tanks that began holding waste in the 1970s showed none of them was leaking.

“None of these tanks would be acceptable for use today. They are all beyond their design life, and yet they’re holding two-thirds of the nation’s high-level nuclear waste,” said Tom Carpenter of the watchdog group Hanford Challenge.