It's not like they just dumped nuclear waste into a hole in the ground. Those reactors are incased in some pretty thick steel, and you can drive into that hole in the ground. It takes all day to move the reactor containments from a barge. There's probably over hundred reactors (fuel removed) from Cruisers and Subs in that hole.
Unfortunately the older containment vessels have cracked and have been leaking radioactive material into the ground and into the river for decades. The problem is going to get worse as those containment vessels age.
It was interesting times in the 1990's and early 2000's when I got old enough to start paying attention to such things and realizing the issues Hanford posed, along with the Umatilla Army Chemical Weapons Depot - the old dirt covered concrete igloos are still there - but in the 1990's they built a facility on-site to incinerate the chemical weapons (mustard gas, mostly as I recall) stored there. Being down stream and down-wind of both there was always that little thought in the back of your head about what would happen if there was an accident. They claimed a poison gas cloud would take 3 or 4 hours to reach the Portland metro most days IF there was a major leak. Thankfully they only had a minor incident during the operation of the incinerator and there was never a gas release, and none of those ancient munitions (dating back to WW2 and older) never let go.
It was mildly disconcerting and amusing when I later learned that across the highway from the depot was the USAF Boardman Bombing Range. I'm sure they always came in on a north-to-south flight path, with the actual targets miles away from the depot and the chances of an oopsie by a pilot dropping a hot load was next to zero.