So I have stayed out of this debate up to this point, but I will add a few thoughts into this discussion. I grew up in the Caribbean (Puerto Rico, Haiti & Dominican Republic) and my Dad spent time in the PR Economic Development Assoc back in the late 60's thru the mid 70's. The US EPA was just getting started in late 71 and early 72. I saw many instances of this "river overflow" in my time, I also noticed that very few if any of the locals ever went in the water when the tannic water was present. My dad told stories for years about how the Economic Dev Assoc would never release info about any story that brought negative attention to tourism. It didn't matter about attacks on US citizens, robberies or a pollution release. He always said to us, when the fisherman don't go out or the lifeguards don't get in the water it's time to stay away from the ocean and spend the day at the pool.
Currently I work for a Global Environmental, Heath & Safety consulting firm, I'm not nor have I ever been an environmental consultant (been selling regulatory compliance services to them for 26 years) but I have learned many things over the years. Having been around many treatment facilities I have experienced the in' sand out's of poo. One thing I have always noticed is that once poo has been treated it doesn't smell like poo. Also one of my co-workers who is an environmental specialist worked in Ochi for 3 years and has been involved in a number of projects around the island. She said to me you would be surprised at the amount of pollution on the Island, in the rivers and how the Gov't has looked the other way to protect the tourism $'s. I also lived in Miami and saw many cruise ships dumping trash and emptying "tanks" offshore. Our waters are nasty all over, we have just done a better job in the last 15-20 years making sure we take better care of the water.
I don't have hard cold facts, but this is what I have experienced in my life with living in the islands and being close to tourism with my dad.