My father, who was in the aircraft refueling industry for decades until his passing earlier this year, would routinely rant about his customers' (the airports, generally) tolerance for leaking jet fuel into the ground.

He reported, and I have no source aside from him, that JFK allows up to 10,000 gallons of jet fuel to leak into the ground. Per day. And he claimed that most airports with hydrant systems had similarly large allowances.