"Under [the U.S.] EPA's regulations, the grounds for terminating a permit include noncompliance by the permittee with any condition of the permit. The transfer of a permit without advance notice to EPA violates a permit condition. Thus, the grounds for terminating WTI's permit or imposing a penalty were present, and EPA could have taken either action or both. In addition, EPA could have decided to take neither action. An agency's decisions on enforcement actions are generally winthin that agency's discretion. (Heckler v. Chaney, 470 U.S. 821 (1986). In this case, EPA chose to impose a penalty of $64,900 on WTI for its failure to notify EPA in advance of adding Von Roll (Ohio), Inc. as an operator. In our view, this choice was within EPA's discretion."