Tank cars shall be unloaded as soon as possible after their arrival at point of delivery, and shall not be used as storage tanks except by permit as set forth in Section 57.105.7 of Chapter 1. Unless otherwise specified by such permit, no tank car containing Class I, II or IIIA liquids shall be allowed to remain on siding at point of delivery for more than 24 hours while connected for transfer operations. During such transfer operations, a qualified person shall be in constant attendance.