Think Dante's Inferno with gauges. The engineers are three years into an eight-year test of how the heat from the stored waste will cook the rock and redirect the flow of liquid through it. This is what they want to hear, since it means the water and any possible contaminants won't percolate up and out as gas or mix with surface water. The idea is that, if subsistence farmers 10,000 years from now were using the local aquifer to irrigate crops and water livestock, they would ingest less radiation per year than they'd get from two dental x-rays. The redesigned groundwater shield that Jim Niggemeyer was describing is one such improvement.
Radiation is basically chaotic movement at the atomic level, and it disorders atoms around it.
That's why the canisters that hold the waste will come apart sometime between 300 and 1,000 years. Diverting groundwater from the decaying canisters seems a good idea. The plan is to make sure at least 200 meters of earthen material sit on top of any given point of the repository. And they want to watch the water. We leave Jim at the mouth of the tunnel, and the rest of us head uphill on a dirt road to eat lunch atop the ridge.