"(a) …any citizen may commence a civil action on his own behalf
(1) against any person … who is alleged to be in violation of (A) an effluent standard or limitation… or (B) an order issued by the Administrator or a State with respect to such a standard or limitation, or
(2) against the Administrator where there is alleged a failure of the Administrator to perform any act or duty under this Act which is not discretionary…"
(CWA, section 505(a))