Here is a picture of the stormwater ditch running alongside Dean Road in Jacksonville, Florida last week after a short rainfall event - probably less than one half inch total. Notice the obvious oil and grease sheen across the surface of the water. The distance from the particular spot the photo was taken to the St. Johns River tributaries is very short - less than a mile.
Most of us don't realize how much the first flush carries into our stormsystems. Intercepting the pollution at the source is important.