Not really. He's actually quite right. It's the same thing as deep well injection. You're talking about materials nearly a mile underground and being capped by nearly a mile of impermeable rock. The risk to human exposure is minute to say the least. Hell it's one of the safest forms of land disposal there is, if not the safest. It's certainly superior to a subtitle C landfill which is pretty much the alternative.
Mott, what of the fluids which return out of the well? You know, the so called produced water?