THE HARTFORD REFINERY IS A COKING REFINERY, WITH THE CAPACITY TO PROCESS 60,000 BARRELS OF HEAVY, SOUR CRUDE PER DAY. THE FLUID CATALYTIC CRACKING UNIT (FCCU) IS THE SUBJECT OF THE VIOLATIONS IN THIS REFERRAL. THE FCCU PROCESSES DIFFERENT FRACTIONS OF CRUDE OIL INTO GASOLINE. THE RESULTS OF THREE CONSECUTIVE STACK TESTS, CONDUCTED ON SEPTEMBER 9, 1993, FEBRUARY 8 AND MARCH 1, 1994, INDICATED VIOLATIONS OF THE PARTICULATE MATTER EMISSION LIMIT OF THE ILLINOIS SIP. A FOURTH STACK TEST, CONDUCTED ON MARCH 22, 1994, AFTER SOME EMERGENCY REPAIRS AND UNDER REDUCED OPERATING CONDITIONS, SHOWED COMPLIANCE WITH THE LIMIT. IN SEPTEMBER 1994, CLARK SHUT THE FCCU DOWN AND CONDUCTED EXTENSIVE REPAIRS TO THE NEW CYCLONES IN THE CATALYST REGENERATOR. CLARK CONDUCTED A FIFTH STACK TEST ON THE REPAIRED FCCU ON DECEMBER 9, 1994. THE RESULTS OF THAT STACK TEST SHOWED COMPLIANCE WITH THE SIP LIMIT. THE ILLINOIS SIP INCLUDES A PERMITTING RENEWAL RULE THAT REQUIRES AN APPLICATION TO BE FILED 90 DAYS PRIOR TO THE EXPIRATION OF THE EXISTING PERMIT. ON FEBRUARY 28, 1994, THE OPERATING PERMIT FOR THE FCCU EXPIRED. ON MARCH 9, 1994, PRIOR TO DEMONSTRATING COMPLIANCE WITH THE PARTICULATE EMISSION LIMIT, CLARK SUBMITTED ITS RENEWAL APPLICATION TO THE IEPA. AFTER THE OPERATING PERMIT EXPIRED ON FEBRUARY 28, 1994, CLARK CONTINUED TO OPERATE THE FCCU, IN VIOLATION OF THE SIP REGULATION T