The SPCC general applicability in 40 CFR §112.1(b) refers to a discharge of oil in quantities that may be harmful, as described in Part 110.  Part 110 is often referred to as the sheen rule.  Does a product or substance have to create a sheen to be subject to SPCC?

The appearance of a sheen is not a necessary factor in determining SPCC applicability. The applicability criteria are based on total oil storage capacity of the facility and reasonable expectation that a discharge would affect navigable waters or adjoining shorelines. For example, the presence of a sludge or emulsion of discharged oil deposited beneath the water’s surface or upon adjoining shorelines, or the violation of an applicable water quality standard also indicates a harmful discharge. See 40 CFR 110.3(a) and (b).