I have wondered why some fuel stations were not built this way.
Some fuel stations have an OWS, some have more elaborate systems than an OWS, the ones I have encountered were not designed for pressure cleaning operations of the fuel pads as detailed by their design engineers and the treated run off goes to storm.
I would be nice to have a "built in" on site system the when we arrive to clean we turn a directional flow valve that would send the wash water to a adequately designed system then to sanitary sewer.
even simple things like drive thrus, at least built and designed to run to one or two particular low points, it would be so much easier, cost effective and possibly reduce storm drain discharge form cleaning activities.
All through the 80 and part of 90 the gas station industry attempted this, does anyone remember car wash Craze on fuel stations? We wondered how they made money? The government through a program tested this on service stations. The bond money was lost and the program was not cost effective.