The owner of a bulk petroleum storage facility discovered that the toluene storage tank (10 feet in diameter and 20 feet in height) was contaminated and would have to be drained and cleaned. Since the tank’s only access portal was located on top of the upright cylindrical tank, the owner decided to have a clean-out access portal installed at the bottom of the tank when emptied. A contractor was called to provide cost estimates for installing the portal. The contractor performed a site survey of the tank and told the owner that the tank must be drained, all sludge removed, and thoroughly ventilated before he would install the portal. The owner directed his maintenance supervisor to get the tank prepared for the contractor.

On the day of the incident the supervisor and an unskilled laborer (a San Salvadorean immigrant on his first day back on the job after working another job for approximately 2 months) drained the tank to its lowest level – leaving 2 to 3 inches of sludge and toluene in the bottom – and prepared for a “dry run” of entry into the tank via the top access portal.

The supervisor rented a self-contained breathing apparatus (SCBA) from a local rental store and instructed the laborer in use of the SCBA and in the procedure they intended to follow. Since a ladder would not fit into the 16-inch diameter access hole, the supervisor secured a knotted, 1/4-inch rope to the vent pipe on top of the tank and lowered the rope into the hole. The 16-inch diameter opening on the top of the tank was not large enough to permit the laborer to enter wearing the SCBA. Therefore, it was decided the SCBA would be loosely strapped to the laborer so it could be held over his head until he cleared the opening. Once entry had been made, the supervisor was to lower the SCBA onto the laborer’s back so it could be properly secured.

Immediately prior to the incident, both employees were on top of the tank. The laborer was sitting at the edge of the opening. The supervisor turned to pick up the SCBA. While he was picking up the unit, he heard the laborer in the tank. He turned and looked into the opening and saw the laborer standing at the bottom of the tank. He told the laborer to come out of the tank, but there was no response. The supervisor bumped the rope against the laborer’s chest attempting to get his attention. The laborer was mumbling, but was still not responding to his supervisor’s commands. At this point, the supervisor pulled the rope out of the tank, tied the SCBA to it and lowered the unit into the tank. Again, he yelled to the laborer in the tank, bumped him with the unit and told him to put the mask on. There was still no response. The laborer fell to his knees, then fell onto his back, and continued to mumble. At this point, the supervisor told the facility manager (who was on the ground) to call the fire department.

The first call went to the police department who relayed it to the fire department. Included in the fire department response was the hazardous materials team, due to the information received about the material in the tank. The fire department (including the rescue and the hazardous materials teams) arrived on the scene approximately 10 minutes after the initial notification. After apprising the situation, fire officials decided to implement a rescue procedure rather than a hazardous materials procedure. Therefore, removal of the disabled person inside the tank was given top priority.

The 16-inch diameter opening at the top of the tank was not large enough to lower a firemen donned in full rescue gear. Therefore, it was decided to cut through the side of the tank to remove the victim. The firemen were aware of the contents of the tank (toluene) and the possibility of an explosion.

The procedure developed by the fire department involved making two 19-inch vertical cuts and a 19-inch horizontal cut with a gasoline-powered disc saw. After the cuts were completed, the steel flap would be pulled down and the victim removed.

While the hazardous materials team was cutting, other firemen were spraying water on the saw from the exterior to quench sparks. Two other firemen were spraying water on the interior cut from the top opening. Three firemen with the hazardous materials team were doing the actual cutting; they were alternately operating the saw because of the effort required to cut through the 1/4-inch thick steel. Sometime during the horizontal cut a decision was made to bring the two firemen off of the top, which meant no water spray on the interior. Simultaneously, the exterior water spray was removed to put out flammable liquid burning on the ground as a result of the shower of sparks from the saw. Thus, at the precise time of the explosion, no water was being sprayed on the saw/cut from exterior or interior. Both vertical cuts were completed and the horizontal cut was 95 percent complete when the explosion occurred.

One fireman was killed instantly from the explosion and several were injured. The man inside the tank was presumed to be already dead at the time of the explosion.