Abstract: A hydrocarbon capturing device includes a retainer that is inserted into the end of an outlet pipe in a storm sewer catch basin. The retainer includes a ring that expands under a bias against the inner surface of the outlet pipe and radially extending fingers mounted to the ring that prevent insertion of the ring into the pipe too far. Two hooks are mounted to the retainer near the upper side of the outlet pipe to fasten one end of a hydrophobic, hydrocarbon-absorbing fabric sheet to the retainer. The opposite end of the sheet extends into the passageway of the outlet pipe, thereby floating atop any water that flows through the pipe during and after a rainfall or snowfall.