If a retail gas station stores gasoline or diesel fuel in both aboveground and underground tanks, what EPCRA thresholds do they apply to determine if they have to report gasoline or diesel fuel on their Tier I or II form?  If they have to report, do they report all the gasoline and diesel fuel at the facility?

Any retail gas station that has at least 10,000 pounds of gasoline or diesel fuel stored in tanks that are not entirely underground must report the total gasoline or diesel fuel at the facility on their Tier I or II form, including any that is stored entirely underground.  Similarly, any retail gas station that has at least 75,000 gallons of gasoline or 100,000 gallons of diesel fuel stored entirely underground must report on the total gasoline or diesel fuel at the facility, including any that is not stored entirely underground.  In other words, whether the facility triggers the threshold for underground storage or for aboveground storage, they report on the total gasoline or diesel fuel at the facility.