Interstate Bank Building Fire;

SPRINKLERS AND STANDPIPE SYSTEM

The building was served by a single zone combination standpipe system with four risers, one in each stairway. The standpipe risers provided a 2 l/2 inch outlet in each stairway at each floor and also supplied 1 l/2 inch hose cabinets in the occupied areas of each floor. At the time the fire broke out the building's fire pumps had been shut down, and the risers had been drained down below the 58th floor to allow a sprinkler line to be connected to a standpipe riser. This job took only a few minutes and the jockey pump was in operation to refill the system when the sprinkler crews noted smoke rapidly filling the stairway. Being only four floors from the roof, the workers went up to the helipad to await rescue.

The sprinkler system was virtually complete on the floors that burned, but the valves were closed between the standpipe riser and the sprinkler system on each floor. During the fire a Battalion Chief was assigned to confer with the sprinkler installation supervisor to explore the possibility of opening these valves to control the fire. It was determined that the fire on the involved floors would probably overwhelm the sprinklers and deprive the handlines of needed water. Eventually, the systems on floors 17, 18, and 19 above the fire were activated, in case the fire extended past the 16th floor.

The four standpipes are supplied by two stationary fire pumps, one diesel and one electric, each rated at 750 gpm at 600 psi pressure. The standpipe system operates with a single vertical zone, depending on the pressure reducing valves at each outlet to control the pressure.

With the main fire pumps shut down, the only water pressure available for the first hoselines was the static head in the risers, and crews reported poor water pressure for the first few minutes. This condition was rapidly corrected when the combination of both building pumps and three Fire Department pumpers were placed in operation.

The building pumps were started manually by the sprinkler installation supervisor who had been rescued from the rooftop by a Police helicopter, taken to a Police facility, and transported back to the scene in a Police car. He arrived at the Fire Department Command Post and informed the Incident Commander of the situation. An engine company was assigned to drive him into the basement loading dock area in a car, to avoid the falling glass, and to assist him in starting the pumps.

The building's two 750 gpm fire pumps drew water from an 85,000 gallon reservoir in the sub-basement. The resupply from the public water supply system was unable to keep pace with the outflow, estimated at over 2,000 gallons per minute, and there were fears that the tank would be emptied.The tank was down to less than one-third of its capacity when the fire was controlled. If the tank had emptied, only fire department pumpers would have been left to supply the standpipes.

The single zone riser system was designed to operate at 585 pounds per square inch (at basement pump discharge) and relied upon the pressure reducing valves to limit the discharge pressure at each outlet on each landing. Problems were encountered with several of these valves allowing excess pressure to be discharged, including one that provided over 400 pounds per square inch. The overpressure caused several hose ruptures and made handlines difficult to control. The heat of the fire caused several aluminum alloy valves in the occupant hose cabinets to fail, creating high pressure water leaks. These leaks took water from the supply that was available for handlines and caused additional water damage on floors below the fire.

It was estimated that a total flow of 4,000 gallons per minute was delivered by the standpipe risers. The total effective fire flow, provided by hoselines attacking the fire, was approximately 2,400 gpm. The attack lines included 1 3/4, 2, and 2 l/2 inch handlines. No exterior streams or master stream appliances were used.

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