Squirrel Chewed Power Line to Water Plant
It was a squirrel that started a chain of events that lead to Tampa’s Water Treatment Facility to stop pumping water to residents and lead to an unprecedented boil-water alert in effect for 37 hours for the entire city. Officials say the squirrel was the first domino, but the squirrel by himself didn’t cause this alone, it was a combination of factors.
Tampa Water Department director Brad Baird said the squirrel crawled into a vertical stand pipe that shields an electrical supply line that drops down the length of a power pole to go underground to the water treatment plant. The squirrel apparently became stuck in the pipe, and, as it tried to turn around and get out, it gnawed into the power supply line. About 5:30 a.m., the line shorted out, killing the squirrel and catching fire. But a water treatment plant the size of Tampa’s is required to have two power service lines from two different Tampa Electric substations. So instead of getting half its power from each, the plant began drawing all its power from the second line, while the utility sent workers to fix the first line. Trouble was, the second line was sagging about 100 yards away from the plant. Then about 1:30 p.m., it sagged close to the line directly below it. Electricity arced between the two. Blue flames rose. In an instant, instead of 13,200 volts going into the plant, there were 26,400. That surge shorted out the second line and caused a third problem. A switch that controls the treatment plant’s backup power exploded and caught fire. Typically, that switch turns on the plant’s diesel-powered generators when, for example, lightning knocks out power from one or both electrical substations — something that happens two or three times a year.
While the water treatment plant has advanced surge protection, this switch was not designed to withstand a surge of twice the power it usually gets, Baird said.Once the switch was knocked out, it took 31 minutes for water plant technicians to get the generators going on a second internal power circuit that serves the plant. During that time, water pressure in the 2,200 miles of city water mains dropped. In some spots, it dropped from 70 pounds per square inch to zero.
The city restored water pressure by 2:30 p.m. Friday, but the chance that untreated water or contaminants had leaked into the system meant that, under health department rules, the city had to advise residents to boil their water until testing showed that it was safe. After tests at 25 spots found no contamination, the city lifted the alert early Sunday.