eCFR Subpart Ka 
[ecfr.gov]
This subpart applies to:
- Petroleum liquids storage vessels with a capacity of more than 40,000 gallons (151,412 liters) that commence construction after May 18, 1978 and prior to July 23, 1984.
Storage vessels constructed, reconstructed or modified after July 23, 1984 are subject to NSPS Kb.
Not subject to this subpart:
- Petroleum liquid storage vessels with a capacity of less than 420,000 gallons (1,589,873 liters) used for petroleum or condensate stored, processed, or treated prior to custody transfer.
Important Distinction:
Petroleum liquids means petroleum, condensate, and any finished or intermediate products manufactured in a petroleum refinery but does not mean #'s 2 through 6 fuel oils as specified in ASTM D396-78, 89, 90, 92, 96, or 98, gas turvine fuel oils #'s 2-GT through 4-GT as specified in ASTM D2880-78 or 96, or diesel fuel oils #'s 2-D and 4-D as specified in ASTM D975-78, 96, or 98a.