Most likely the gas tanks are still buried under the ground, and whatever was in them when it closed is still there until eventually they leak. Here in California the state that believes they have to protect us from ourselves. Even gas stations in the 1960s had to put double wall tanks in, and then by the 19'80s you had to have a liner with a gravel bed a double wall tank and a gas leak detection system. If that system triggered more than so many times in a year it required you to dig up the tanks. That happened to a small Shell station near where I live. It was the old fashioned two car garage with the hydraulic floor lift. Had been here since the early 60s. The original tanks leaked the owner came up with the money to replace them, after spending almost a half million dollars to replace the tanks. 2 years later the gas detector started going off saying there was a leak. His insurance company refused to cover the cost of the repairs, he somehow found the money to have one tank dug up and repaired, turned out to be a bad fitting installed by the manufacturer. 3 years later there was another leak. This time he couldn't afford to have them repaired. Station was sold the old tanks removed everything was leveled, there's absolutely no Trace there was ever a gas station at that corner. It's now a Starbucks. And we prove that it ever existed or a few photos I took as a young kid.