There is so much gear including lead on the bottom of most rivers it would blow your mind. The lead is like gold it moves to the center of the river line and acumulates in natural catch points and that is where it stays. If it was going to kill off a river the kenai would be dead. I bet there is close to a ton of lead in beaver creek hole alone. That section sees thousands of 6-12 ounce lead balls in one month. Many stay there. I picked up nearly a half of a five gallon bucket full of just spinners and spoons last spring up river of Soldotna at a not so popular spot for silvers. I picked up a coffee can full of leaded trebels at a popular snagging spot near town. The steel rusts away but the lead is there for ever.