In London we approach this issue at a regional level, because it's certainly a regional problem.
The sources of phosphorus going into the watershed are many. In London, around 15% is coming from urban sources, so we certainly contribute our fair share to the problem. A lot of that is coming through the wastewater treatment plants, and it's certainly coming through when we have overflow events. In some areas of our city that are older, we have combined sewers that are overflowing. They flow directly into the river. It's a very bad situation. We're working to separate those, and that's part of resolving the issue in terms of phosphorus.
There is a push at the provincial level, and I think almost an expectation, that we'll move to tertiary treatment for all wastewater treatment plants. We believe we have a better way of doing it that is cheaper and is going to solve the problem. We want to pilot that. In London, we have a great firm, Trojan Technologies, that works on wastewater treatment and sells all over the world. They have a suggestion about how we can bolt their technology onto our existing plants. It's going to be a lot cheaper. It probably will get us down to 0.1 milligrams per litre of phosphorus, which is a reduction of about 75% in what we have coming out of the wastewater treatment plants now. If that works, I think it will help with the urban sources.
The other parts of this are primarily rural. In southwestern Ontario, you are in the heartland of agriculture. There's a lot of farming going on, and there's runoff that comes from those operations. That's tougher to deal with, because a lot of it's coming off private properties owned by many different people, and a lot of the solutions are not easy to implement on private property.
Some of the solutions, such as tertiary treatment, are expensive. We don't think that's the right approach. We want to go with a more cost-effective approach that's going to let us achieve those targets. Hopefully, that pilot will prove out and other municipalities can benefit from it.