A harmful quantity is any quantity of discharged oil that violates state water quality standards, causes a film or sheen on the water’s surface, or leaves sludge or emulsion beneath the surface. Under EPA regulations, reporting oil discharges does not depend on the specific amount of oil discharged but on the presence of a visible sheen created by the discharged oil. As a rule of thumb, a light fraction of petroleum will create a sheen on water at or above 15 ppm (parts per million).
