I. SYNOPSIS OF THE CASE CENTRAL ILLINOIS PUBLIC SERVICE COMPANY ( CIPSCO ) AS AN ILLINOIS CORPORATION DOING BUSINESS IN COFFEEN, ILLINOIS. CIPSCO'S PUBLIC UTILITY FACILITY IS LOCATED IN MONTGOMERY COUNTY, WHICH HAS BEEN DESIGNATED AN ATTAINMENT AREA FOR SO2 BY THE USEPA. CIPSCO'S COFFEEN GENERATING STATION SUPPLIES ELECTRICITY TO MUCH OF RURAL ILLINOIS. THE COFFEEN STATION HAS TWO COAL-FIRED BOILERS AND ELECTRIC GENERATING TURBINES, DESIGNATED UNITS 1 AND 2. NEITHER UNIT 1 NOR 2 HAVE ANY SUL FUR DIOXIDE ( SO2 ) EMISSION CONTROL EQUIPMENT. BOTH UNITS FIRE HIGH-SULFUR ILLINOIS COAL FROM THE MONTEREY MINE NEAR CARLINVILLE, ILLINOIS. ON AUGUST 13, 1985, DAVID SCHULZ, ENVIRONMENTAL ENGINEER, AIR COMPLIANCE BRANCH, USEPA, CONDUCTED AN INSPECTION OF THE COFFEEN STATION. SEE ATTACHMENT 1. BASED UPON HIS INSPEC- TION AND A REVIEW OF COAL ANALYSIS DATA FOR THE COFFEEN STA- TION, AN ENGINEERING CHECKLIST RECOMMENDED THE ISSUANCE OF A NOTICE OF VIOLATION ( NOV ) TO CIPSCO. SEE ATTACHMENT 2. ON OCTOBER 11, 1985, THE NOV WAS ISSUED. SEE ATTACHMENT 3. THE NOV CITED CIPSCO FOR, AMONG OTHER THINGS, VIOLATION OF ILLI- NOIS RULE 204 WHICH LIMITS SO2 EMISSION TO 6.0 POUNDS PER MI LLION BTU (LB.MMBTU)> THE NOV WAS AMENDED AND REISSUED ON MAY 21, 1986. SEE ATTACHMENT 4. THE AMENDED NOV REFLECTS THE AGENCY'S MOST RECENT RULEMAKING ON SO2 EMISSION LIMITA- TIONS UNDER THE ILLINOIS SIP. SEE A