This article says it is leaking into the ground
“Before the last of the pumpable liquids were removed from single-shell tanks in 2004, an estimated 1 million gallons of waste leaked or spilled from the tanks and their distribution systems. Some of that has reached the groundwater, but movement from central Hanford to the Columbia River five miles away is slow.”
The federal government already spends $2 billion each year on Hanford cleanup one-third of its entire budget for nuclear cleanup nationally. The Energy Department has said it expects funding levels to remain the same for the foreseeable future, but a new Energy Department report released this week calls for annual budgets of as much as $3.5 billion during some years of the cleanup effort.