In June 1978, at a South Carolina resort, a young woman wearing only a bathing suit was observed in the early evening stepping into an illuminated water fountain. The fountain was circular with a diameter of 16 feet and a maximum depth in the center of about one foot. She suddenly collapsed and was unable to stand up.
Three of her similarly dressed companions stepped into the fountain in quick succession to help her and each in turn collapsed. They could not be readily removed because bystanders received severe electrical shocks from the water when they attempted to enter the fountain barefoot. The water was energized at the service voltage. The fountain's concrete bottom, coated with fungus and algae, was extremely slippery.
No one knew how to kill the power in a hurry. It took 10 to 15 minutes for rescuers wearing rubber boots to get the first person out of the energized fountain. The four young women who had entered the fountain and collapsed had died of electrical shock. Some were found with their arms in flexion in the "pugilist" position. The shocking currents were the result of potential gradients, or voltage differences between their feet in the water. The fault current traveled up one leg, flowed through the torso of a victim, and then exited out of the other leg back into the water. A shocking current as low as 20 milliamperes could cause paralysis of the leg muscles, with the resulting fall of a walking person. This would be followed by breathing paralysis while lying in the water, with ensuing asphyxiation and cardiac arrhythmia.
The well-established duration of 10 minutes in an oxygen-deprived state before a person's brain damage becomes irreversible, and the lack of a readily accessible disconnect switch, as called for in Rule 380-8 of the 1968 National Electrical Code (NEC), clearly identified as called for in Rule 110-22, were fundamental causes of the deaths of the four young people.
An after-accident inspection established that the noncurrent-carrying metal parts of a light fixture, pump motor and junction box submerged in the fountain were not bonded with a grounding conductor back to a panelboard in the fountain equipment room. Lack of grounding and bonding violated Rules 250- 42, 680-4, -7, and Ð8 of the 1968 NEC, which was in effect when the fountain was constructed. Article 680 was devoted to swimming pools. Fountains had not yet been included.
Upon removal of the junction box's gasketed cover, the energized 115-volt conductor was found welded to the inside wall of the junction box. This was the cause of the "hot" condition of the water in the fountain, which could have existed for weeks or longer. A photoelectric cell controlled the electricity to the fountain. Thus the water was not energized for most of a typical day. If the fountain's electrical equipment had been grounded as required, either the circuit breaker at the panel box would have tripped open or the water's potential gradient due to the fault would have been decreased to a low level.
The submerged junction box contained water, and had tarnished conductors and wire insulation covered with a corrosion-type scale. Thus the adequacy of the design, construction and gasketing arrangement for the junction box was called into question. Several descriptions of underwater light systems in the junction box manufacturer's brochure indicated the desirability of encapsulating wires so that they not touch the sides or walls of the shell.
The 1968 NEC stated under Rule 680-4 (g) that avoiding a shock hazard during a fault in an underwater lighting fixture could be assured by either the design and construction of the fixtures or by the use of a ground fault circuit interrupter (GFCI). No other components in underwater installations such as submersible pumps or junction boxes were considered in the 1968 NEC. The design of the fountain's electrical supply for the pump and underwater light elected to not incorporate a GFCI, but instead to rely on selection of appropriate fixtures. The county in which this event took place adopted the 1971 NEC in 1974, and initiated requirements for electrical inspections at that time. At the time of the accident, there were as yet no licensing procedures for electricians and building contractors. However, it was only in Article 680D of the 1975 NEC that fountains were included for the first time. GFCIs were now mandatory, instead of optional, in a branch circuit supplying fountain equipment. Under the 1975 NEC, Rule 680-42 (b) (3) required that the junction box be filled with a potting compound to prevent the entry of moisture.
Considered the substantially increased hazards of electricity in wet environments, final inspection and maintenance were inadequate in this situation. EC
MAZER is a consulting electrical engineer who specializes in electrical safety issues. He may be reached at 202.338.0669 or email@example.com.