This article says it is leaking into the ground
Also
“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.
http://www.startribune.com/nation/192588151.html?page=2&c=y