A small airport I used to fly out of switched to an aboveground tank when the old underground one was found to have a leak. The permitting and construction cos

A small airport I used to fly out of switched to an aboveground tank when the old underground one was found to have a leak. The permitting and construction costs for an underground tank were much higher with double walls and I believe sensors to detect leaks. The rationale was exactly as you say -- with an aboveground tank you can easily see fuel leaking out and fixing a leak is also very easy by comparison.