There area a couple of things. First, we have to decide which ones we're going to assess, and then we do an assessment on those. Then we look at things like the degree of contamination, who's going to be affected by it, and frankly some of the practical realities of addressing the situation. We try to identify those sites where we think spending the dollar will give us the biggest bang for the buck.
It's always a little bit difficult when you put competing pressures in there, but we do try to find the ones where we think each dollar we spend gives us the maximum benefit. I don't have the full list of criteria we use but that would be the basic element, where the contamination is the most serious and where we can have the biggest impact by cleaning them up.