Swimming in the Rain

So I just got back from Race Registration and Packet Pickup for the 2005 New York City Triathlon, where I got my free t-shirt, free water bottles, free Heel Balm and free Butt Paste (not kidding).

Two years ago, they cancelled the swim portion. Apparently there were unsafe levels of E. coli in the Hudson River (go figure) due to heavy rain on the days leading up to the race. It's been raining pretty heavily today, and it's supposed to rain a little bit tomorrow, but according to the race officials, the swim will definitely take place this Sunday.

That makes me wonder... What qualifies as a safe level of E. coli to swim in?