ON APRIL 16, 1973 THE ARIZONA DEPARTMENT OF HEALTH ISSUED A CERTIFICATE OF APPROVAL TO CONSTRUCT A SEWAGE TREATMENT PLANT AT KACHINA VILLAGE SUBJECT TO THE CONDITION THAT THE PLANT EFFLUENT CONCENTRATION OF PHOSPHORUS BE LESS THAN 1.0 MG/1. BY LETTER OF 10/10/73 THE DESIGN CONSULTANT FOR THE PLANT, WHEELER, PETERSON & COFFEEN, STATED THAT THE PLANT WAS DESIGNED TO MEET A 3.0 MG/1 PO4 EFFLUENT CONCENTRATION. IN A LETTER DATED 11/29/73 FROM THE ARIZONA DEPARTMENT OF HEALTH, THE STATE EXPLAINED THAT BECAUSE OF TERTIARY TREAT- MENT REQUIREMENTS OF ANY DISCHARGES IN THE OAK CREEK AREA, A 3.0 MG/1 PO4 INSTANTANEOUS LIMIT IS NEEDED IN THE KACHINA VILLAGE NPDES PERMIT. THE STATE OF ARIZON HAS ADOPTED AND THE EPA HAS APPROVED WATER QUALITY STANDARDS FOR THE BODY OF WATER INTO WHICH THE DEFENDANT IS PERMITTED TO DISCHARGE. THE KACHINA VILLAGE IMPROVEMENT DISTRICT APPLIED FOR AN NPDES PERMIT ON APRIL 8, 1973, FOR THE DISCHARGE OF MUNICIPAL WASTEWATER FROM THEIR SEWAGE TREATMENT PLANT (HEREIN CALLED STP) TO THE PUMP HOUSE WASH, A WATER OF THE UNITED STATES. THE PUMP HOUSE WASH IS A TRIBUTARY TO OAK CREEK, WHICH IS A TRIBUTARY TO THE VERDE RIVER. NUTRIENT STANDARDS FOR THE VERDE RIVER AND ITS TRI- BUTARIES SPECIFY LIMITS ON PHOSPHOROUS CONCENTRATES. ON MARCH 15, 1974, EPA, REGION IX, S & A DIVISION PER- SONNEL CONDUCTED A SAMPLING INSPECTION AT THE STP AND FOUND THAT THE PLANT WAS NOT MEETING THE PO4