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Today's practice question

Wednesday, 23 September 2026
CSP · Environmental Management
An oil sheen is observed on a stormwater outfall discharging to a river. Under the CWA, what does the 'sheen rule' require?

Explanation

Under the Clean Water Act 'sheen rule,' a discharge of oil that causes a visible sheen (or film or discoloration) on water must be reported to the National Response Center - a visible sheen is the trigger for reporting. Ignoring it, diluting to hide the sheen, or merely keeping an internal record all violate the requirement. A visible sheen is reportable to the NRC. (Ref: 40 CFR 110; sheen rule.)
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