An incident involving external floating roof tanks highlight the risks associated with open and closed roof drain valves.

A gas detector alerted operations to a possible hydrocarbon leak near the tankfarm area. Shift personnel immediately investigated the area and found gasoline/condensate escaping from the roof drain outlet at one of the double deck floating roof tanks. The gas cloud that formed had triggered a nearby gas detector. The release led to excess emissions and a difficult cleanup but no injuries.

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