I hear what you're saying, and I'm not trying to argue with you. But think of Fukushima, and how that unfolded. Multiple failures that were never envisioned. Now think of Chernobyl, and the mitigation to protect the water table, and the engineering solution. Now this isn't a nuclear contamination problem, I get it. But you are still dependent long term on no failures of electrical/mechanical mitigation. Maybe you seal the bottom of the quarry, and maybe that is ridiculous and can't happen, I don't know. But I do know that this type of mitigation will inevitably lead to failures, and you won't see them coming. The solutions currently used are band aids, maybe the best that can be done now, but they are not long term. The ideal long term solution will be passive and simple in design, and will take a different approach to solving the problem.