Section 309(a) of the Clean Water Act (CWA), 33 U.S.C. Section 1319(a), provides that, whenever the United States Environmental Protection Agency (EPA) finds that any person is in violation of any condition or limitation which implements, inter alia, Sections 301(a) and 402 of the CWA, 33 U.S.C. Sections 1311(a) and 1342, the EPA may issue an order requiring such person to comply with such condition or limitation, and shall specify a time for compliance that the EPA determines to be reasonable.