I have NEVER used the products, however when I was in AZ round table, I saw gas stations that had it on their gas pads. I noticed my ECCO shoes had the stuff all over the sole. My soles of my shoes carried the stuff in the car on the rug, marking my interior rug. You could also see the tire marks ( In Gray Color) leaving the gas pad driving away to the asphalt marking the asphalt with Grey Tire Marks for about 40 to 70 ft.
We in turn get the same results with our methods and there is no powder residues when you pressure wash. There is also a question however about if your client wets the surface down / rains really hard or they happen to pressure wash. I am positive that if you put this down the storm drain, and if some time later, the client was to hose it down or pressure wash the area, an issue would exist from the run off in regards to the "Clean Water Act".
This product is not a cure all, it is a cosmetic temporary fix. The SRWQCB is looking into this product and their initial views are not promising due to run off residue. This and other similar products is not widely used here,. In fact I have never seen it used here due to the run off issues. In dryer states such as Arizona, you see it used at many Gas Stations.
Thats my 2 cents !