Officials don’t know exactly why or precisely where, but they do know that “liquid levels in Hanford single-shell tanks (SST) T-111 are decreasing.” That’s not an ideal situation, in case you weren’t up to speed on the Hanford Nuclear Waste Site in Washington State.

The U.S. Dept. of Energy Office of River Protection and its Tank Farms operations contractor, Washington River Protection Solutions, had thought the leaking was under control since the last known leak in 2005. But as crews still tried to quickly move radioactive waste from the 177 underground tanks, put into service in the 1940s, into more secure double-shell tanks, they apparently can’t move fast enough.

While monitoring wells in the T Tank Farm, where Tank T-111 is located, hasn’t popped up any “significant changes in concentrations of chemicals or radionuclides in the soil,” and heavy soil and water filtration systems are in place for the area to keep the Columbia River as clean as possible, that doesn’t diminish the concern that a single-shell tank is leaking radioactive waste directly into the soil.

Tank T-111 is a 530,000-gallon capacity underground storage tank built between 1943 and 1944. It was put into service in 1945 and still holds roughly 447,000 gallons of sludge, a mud-like mixture of solid and liquid radioactive waste from years of nuclear service and plutonium production.

Thank tank was classified as an “assumed leaker” back in 1979 and interim stabilization wrapped up in 1995, a process that pumped out all liquids from the tank. But the liquid/sludge levels have continued to decrease by as much as potentially 300 gallons a year, coming as a bit of a surprise. Gov. Jay Inslee spoke Friday, stating he’s concerned about the integrity of the other single-shell tanks at Hanford and plans a trip to Washington, D.C., this week to discuss the matter with Secretary Steven Chu.

"I am alarmed and deeply concerned by this news,” he wrote in a statement. “This was a problem we thought was under control, years ago, when the liquids were pumped from the tanks and the sludge was stabilized. We can't just leave 149 single-shell tanks with high-level radioactive liquid and sludge siting in the ground, for decades after their design life.”

With Bechtel’s $12-plus billion vitifrication plant still behind schedule due to technical concerns, the act of converting the waste into vitrified glass for safe long-term storage isn’t ready, not that crews have fully devised methods for cleaning out every last gallon of waste from these highly toxic underground storage tanks.

“This news is a sharp reminder, a wakeup call, that we can't be complacent, or waiver in any way, on our nation's commitment to clean up Hanford,” Inslee states. “I know this is a time of tight budgets, but with an active leak of high-level radioactive material into the environment, money can't be an excuse for inaction.”

And as the Hanford budget remain precariously perched, unfortunately the plot there thickens. And leaks. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He has also written for TIME, Popular Mechanics, Popular Science and more. You can follow him on Twitter at @tdnewcomb or visit his website here.