THE PROCTER AND GAMBLE MANUFACTURING COMPANY OWNS AND OPERATES A MANUFACTURING FACILITY IN SACRAMENTO, CALIFORNIA. AT THE FACILITY, P&G OPERATES A HYDROGENATION FOR METHYL ESTERS OF COCONUT OIL. DURING THE HFA PROCESS, METHANOL, WHICH IS A VOLATILE ORGANIC COMPOUND, IS EMITTED TO THE ATMOSPHERE. VOCS ARE A PRECURSOR TO GROUND LEVEL OZONE. ON MAY 11, 1982, P&G APPLIED FOR AN ATC TO THE SMAQMD TO MAKE NUMEROUS MODIFICATIONS AT THE FACILITY, INCLUDING INSTALLATION OF A SOUTH CENTRIFUGE TO BE USED IN THE HFA PROCESS. IN ITS ATC APPLICATION, P&G ESTIMATED THAT TOTAL METHANOL EMISSIONS FROM THE FACILITY WOULD DECREASE BY 4,282 LB/YR. ON JUNE 22, 1982, SMAQMD ISSUED A 1-PAGE ATC TO P&G FOR THE MODIFICATIONS REQUESTED IN P&G'S ATC APPLICATION. THE ATC CONTAINED NO EMISSION LIMITS, AND DID NOT REQUIRE P&G TO INSTALL EQUIPMENT THAT COMPLIED WITH BACT. P&G COMMENCED CONSTRUCTION OF THE SOUTH CENTRIFUGE IN JUNE 1982, AND BEGAN OPERATION OF THE SOUTH CENTRIFUGE IN AUGUST 1983. IN 1990, P&G ENTERED INTO A CONTRACT WITH THE MIDWEST RESEARCH INSTITUTE WHICH PROCEEDED TO CONDUCT A STUDY OF ROC EMISSIONS FROM P&G'S FACILITY IN AUGUST 1990. MRI PREPARED A REPORT IN OCTOBER 1990 THAT IDENTIFIED THE CENTRIFUGE VENT TANKS AS SIGNIFICANT SOURCES OF METHANOL EMISSIONS. MRI ESTIMATED THAT METHANOL EMISSIONS FROM THE SOUTH CENTRIFUGE VENT SEAL TANK TO BE