Supposedly the soil degrades it in a very short time. Some people use glyphosate on their pond banks with no apparent ill effects. It would probably take a gallon of pure glyphosate to get you 1ppm in a fair sized pond.
There is some question about Roundup brand having a harmful surfactant. I don't guess it's harmful 50 feet from your pond. Surely it would break down in the soil. Certain groups love to get chemicals banned. If it really was harmful, it would surely be banned by now.
