The SDWA and its implementing regulations are not concerned with whether an injected fluid is itself contaminated. Rather, they are concerned with the result of "injection activity." A permit applicant must show that the proposed activity will not allow "the movement of fluid containing contaminant." Id. Injections of clean water into the ground can cause the movement of contaminants into an aquifer. For example, contaminants may dissolve into clean water as the injected water passes through the soil on its way to an aquifer.