^^^Still, there is not enough pollutants to show up on any study, which makes sense, because there's way too much water for there to be any significant traces of oil/fuel. From what you're saying, its the oil. Fine, lets say for example I burn 10 gallons of fuel in a day at the lake and I'm using a 50:1 ratio. 30% comes out unburned, according to the enviros. Thats 3 gallons, with a 50:1 ratio. So 0.06 gallons of oil is what I put into the lake approximately. There's something like 4 trillion gallons of water in Lake Mead. So how many people like me would have to show up and ride in a day before there is even a measurable trace of oil in the water? Well, by my math, if 1 million people like me showed up and rode in a single day, you would be able to measure about 0.000000015% oil in the water. I'm not sure what an acceptable level is, but I'm pretty sure that 15 billionths of 1 percent of oil is not going to hurt a fly (ignoring for a minute that it probably takes 5 years before 1 million 2 stroke riders have launched their skis).