THE MOBIL OIL CORPORATION OWNS AND OPERATES SEVERAL PETROLEUM LIQUID STORAGE VESSELS AT A PETROLEUM REFINERY IN TORRANCE, CALIFORNIA. THE STORAGE VESSELS AT THE REFINERY CONTAIN PETROLEUM LIQUIDS IN VARIOUS FORMS SUCH AS GASOLINE AND CRUDE OIL. MOBIL OPERATES TWO EXTERNAL FLOATING ROOF PETROLEUM LIQUID STORAGE VESSELS AT THE REFINERY THAT ARE AFFECTED FACILITIES PURSUANT TO THE ACT'S NEW SOURCE PERFORMANCE STANDARDS. THE RELEVANT NSPS REGULATIONS ARE SET FORTH AT 40 C.F.R. PART 60, SUBPART KA. THESE VESSELS ARE EQUIPPED WITH SLOTTED GUIDE-POLES WHICH EXTEND THROUGH AN OPENING IN THE ROOF. PURSUANT TO 40 C.F.R. SECTION 60.112(A)(1)(III), ALL OPENINGS IN THE ROOFS OF MOBIL'S EXTERNAL FLOATING ROOF STORAGE VESSELS MUST BE EQUIPPED WITH A COVER, SEAL OR LID WHICH IS TO BE MAINTAINED IN A CLOSED POSITION AT ALL TIMES (I.E. NO VISIBLE GAP) EXCEPT WHEN THE DEVICE IS IN ACTUAL USE. THE SLOTS IN THE GUIDE-POLES ARE VISIBLE GAPS THAT ALLOW THE RELEASE OF VOC EMISSIONS INTO THE ENVIRONMENT. MOBIL HAS VIOLATED THE NSPS SUBPART KA REQUIREMENT BY INSTALLING AND OPERATING ITS SUBJECT TANKS WITH THESE VISIBLE GAPS. IN ADDITION, MOBIL OPERATES FOUR PETROLEUM LIQUID STORAGE VESSELS THAT ARE AFFECTED FACILITIES PURSUANT TO NSPS SUBPART KB AND ARE SUBJECT TO THE REQUIREMENTS OF SECTION 60.112B(A)(2)(II). THESE VESSELS ARE ALSO EQUIPPED WITH EXTERNAL FLOATING ROOFS AND SLOTTED GU