how much chlorine (free/total) is allowed in a creek for normal health of the creek?

Answer 1

that is a very simple answer. 0.0 mg/l of free CL2(chlorine). Now for total CL2 it might be possible for a small amount, something like 0.3 mg/l to be run off into a creek or river. The way you asked the question leads me to believe that you know the difference between the Free and Total CL2 residuals. So you will know that a Free CL2 in a water system means that there is enough CL2 in the water to kill all organisms and still have some left over. This would kill not only the fish but all food sources such as algae and bacteria. A low Total CL2 reading would show that while there is some CL2 in the water there is not enough to do major damage to the eco-system of the creek. But all things considered you would not want any CL2 at all in a creek/river/lake. CL2 needs to be controlled as it is very dangerous when not used correctly.