1.Ahmad owns a Spin-N-Market in Texas, a convenience store and gas station. One of the Spin-N-Market's gasoline tanks developed a leak. Jewel McCoy of CIT Environmental Services inspected the tank and said it needed to be drained and then pumped. McCoy gave Ahmad the cost of draining, and he suggested he would do it himself despite McCoy's warning about violations of the law. Ahmad rented a pump at the local hardware store and pumped over 5,000 gallons into a manhole near his store (4,690 of those gallons were gasoline). The gasoline made its way to the storm sewer system and then a creek as well as the city sewage treatment center. While firemen were working to divert the gasoline, the treatment center and two nearby schools had to be evacuated. Ahmad was charged with violation of the Clean Water Act and was convicted of two charges. Ahmad raises the defense that he did not know that he was pumping gas, that he thought that he was pumping water. What issue is he raising as a defense? Is his defense valid? [United States v. Ahmad, 101 F.3d 386 (5th Cir.)]