Regarding the June 26 article on mysteriously rising waste levels in Hanford tanks. The tanks are giant tin cans, 75 feet wide, with several risers, which are long pipes that go fom the top of the tank to the surface through about 12 feet of soil that covers the tank.
The risers are capped with various devices that also act as seals. The tank level measurements are from the top of a riser flange to the top of the waste. The distance from the flange to the waste is the "level."
How can that distance change? Do you see where I'm going with this? Think of a tin can, 75 feet in diameter with 12 feet of dirt on top of it, and then periodically drive some vehicles over it. Over a period of years, it will probably sag, and the distance between the waste and the flange will be less, thus giving the impression of rising waste level. This phenomenon could easily explain the small "increases" in the tank level. There are probably other reasons for mysterious level increases, but absent any other data, this explanation seems the most likely. Check it out, Hanford.
George Block, Kennewick