hi there
we have several sites by us, the majority being in defunct petrol stations,
these sites already have interceptors installed, and would be emptied regularly of the contaminents, oil etc.
the sites are predominately staffed by our european friends, they work extremely hard and do a good job, family size car, inside and out £10.00, with the sites being open 7 days a weeks nearly 12 hours a day.
someone has struck it lucky with this concept, and is doing very nicely.
a lot of the money is being sent back home, so good luck.
the supermarket and shed car park operations seem to be a variation on this theme.
regards
martin