KELCO, A DIVISION OF MERCK & CO., INC., OWNS AND OPERATES A KELP PROCESSING AND BIOGUM MANUFACTURING FACILITY IN SAN DIEGO, CALIFORNIA. THE FACILITY, WHICH CONSISTS OF AN ALGINIC FIBER PLANT, 3 COMMERCIAL PLANTS, 2 PILOT PLANTS, AND A COGENERATION PLANT, MANUFACTURES VARIOUS ALGIN PRODUCTS BY PROCESSING SEA KELP HARVESTED OFF THE CALIFORNIA AND MEXICO COASTS, AND PRODUCES SEVERAL BIOGUMS BY A PROCESS OF BIOPOLYMERIZATION. ISOPROPYL ALCOHOL, PROPYLENE OXIDE, AND PROPYLENE GLYCOL, WHICH ARE VOLATILE ORGANIC COMPOUNDS AND PRECURSORS TO GROUND LEVEL OZONE FORMATION, ARE EMITTED TO THE ATMOSPHERE DURING THE MANUFACTURING PROCESS. KELCO'S FACILITY IS THE LARGEST STATIONARY SOURCE OF VOC EMISSIONS IN SAN DIEGO, COUNTY, ACCOUNTING FOR APPROXIMATELY 36% OF SAN DIEGO'S TOTAL EMISSIONS FROM STATIONARY SOURCES ACCORDING TO THE 1991 EMISSIONS INVENTORY. KELCO MODIFIED ITS PILOT PLANT NO. 2 IN 1982 AND 1988 WITHOUT OBTAINING AN ATC FROM SDCAPCD. THE MODIFICATIONS EXPANDED THE CAPACITY OF PILOT PLANT NO. 2 AND RESULTED IN VOC EMISSION INCREASES ABOVE THE NSR THRESHOLD. KELCO ALSO MODIFIED PLANT B IN 1989 AND PLANT C IN 1991 PURSUANT TO ATCS ISSUED BY SDCAPCD. THE MODIFICATIONS RESULTED IN VOC EMISSION INCREASES THAT EXCEEDED THE NSR THRESHOLD. HOWEVER, THE ATCS FOR THE PLANT B AND C EXPANSIONS DID NOT REQUIRE KELCO TO INSTALL EQUIPMENT THA