[harry-wood]

The bit about petroleum solvents, makes me wonder about sinkholes. "causes it to dissolve and break down into a non-load-bearing sludge", so if some joker tips a bottle of that in the park then a sludgy hole in the ground will start forming?

[mikewarot]

If there is any reasonable amount of soil above it, I suspect the bacteria and fungi will eat it well before it gets down to the foam.