I would say it has been very unsuccessful.
I had a small role in a 2004 review of the program. It was largely done by three federal scientists from the fisheries and environment departments. Of a 100-page report, about 99 pages were scathing criticisms of how they changed chemical analyses, changed sites of sampling, changed timing of sampling, all the things that violate all of the first principles of monitoring programs.
What I've heard since from people who have been involved leads me to believe that it hasn't improved very much. The other thing I find deficient in the program is that it's not transparent. There have been no analyses of the data. The data are not available to the scientific community at large to analyze and there has been no public release of what the program shows. Probably if there were, because of the deficiencies in design, it would show nothing. You can show no effect either by designing a very poor study or by nothing happening, and my guess is it's the poor design that's at fault here.
I think that program really needs to be changed. I would recommend an oversight by an independent committee of scientists and some first nations representatives, and that the program be required to report every three years, perhaps, with a public report as well so that people can understand what's happening to the river, if anything.