Abstract: On February 14, 1997, during the shutdown/turnaround period for an unsaturated gas plant, Delta Tech, the contractor, completed a water/chemical wash of debutanizer tower 8C-6 and heat exchanger 8E-39. At approximately 8:05 a.m. on February 15, 1997, Employee #1 was requested by the control room of the unsaturated gas plant to drain any water/chemical residues from heat exchanger 8E-39. Employee #1 drained the material through the heat exchanger's bottom drain valve into the refinery's sewer. As the residue was released, it changed into gasoline. Once the supervisor took notice of the gasoline, he attempted to close the bottom drain valve. The valve bushing broke and Employee #1 notified maintenance that assistance was needed to close the valve. Maintenance responded by putting in a sipe valve and tapping it into packing. Mobil's fire brigade and its safety and emergency response team brigade were notified and barricade the immediate area around the debutanizer and heat exchanger. Industrial hygienists monitored the perimeter and sewer system for benzene, with results indicating levels between 1.9 and 11.6 benzene. Employees #1 through #9 were taken to a medical clinic for benzene testing. Urinary phenol evaluations indicated levels that did not require additional testing.