Natural Resources committee  They overlap in some cases, but there are other places where they're independent.

Natural Resources committee  No, there was a joint federal-provincial exercise a few years ago to try to come up with the key aquifers and then to attach a priority to the sequence of them. We have changed that priority a little bit. For example, we're not dealing with one that's close to the oil sands, because of concerns about whether there's an interaction between them.

Natural Resources committee  Yes. We're still working on others, but 12 have been completed.

Natural Resources committee  Yes.

Natural Resources committee  Yes, I can certainly understand how the logic follows from that. From a scientific perspective, though, I would say there's a slightly different view. We know that things like gas contamination of an aquifer occurs in places, and the cause of that can actually be determined scientifically.

Natural Resources committee  I'm talking about the logic of it. We can't possibly know what's happened, because we had to have studied everything in advance. I'm saying there is actually a way of telling where methane came from, and some of the things that have been talked about, in terms of potential contamination near oil and gas developments, have actually been shown to be biologically determined or to have created methane from the near surface.

Natural Resources committee  Right, not things from reservoirs.

Natural Resources committee  Right.

Natural Resources committee  Thank you, Mr. Chair. We're the scientific arm of Natural Resources Canada, so we restrict ourselves to trying to provide the facts and make sure they're publicly available.

Natural Resources committee  The way to try to answer your question is to talk about some of the geological knowledge we have. I'll turn to Monsieur Lavoie in a second to talk about how we know that reservoirs are under impermeable layers. The geology has acted to trap highly mobile materials over time. So that's part of the knowledge that we have, that there is a geological understanding of how long fluids and gases have been trapped in the subsurface, and they're trapped quite effectively.

Natural Resources committee  We're not the exact experts to answer that with a clear answer, but I can tell you that there are regulations and requirements for the industry to monitor their fracturing process. For example, they have to have sensors close by to the hole to monitor how large a motion in the ground is created by the fracturing of the rock, and they can tell how far the fractures extend.