ROCK FALLS, Ill. — The Illinois Department of Natural Resources says a disconnect switch failure is partly to blame for the power outage Monday at the Sinnissippi Dam Control Building. The power outage caused the dam gates to unintentionally open, lowering the water levels in areas of the Rock River.
According to the IDNR, the exact time of the failure is unknown. They believe the dam control building lost power around 3 Monday morning. A disconnect switch in the transformer, which supplies power to the building, failed. The backup generator kicked in, but it only ran for about three hours before a high-temperature fault caused it to overheat. That happened at approximately 5:45 a.m.
"Without any power, the compressors that supply air to the dam stopped operating, allowing the gates to unintentionally open," Jayette Bolinski, the IDNR director of communications, said in an email to News 8.
Water levels in the upper pool of the Rock River began to drop. Its lowest point was reported by the USGS at 11:30 a.m. Monday at 4.83 feet. That was a drop of nearly a foot and a half.
An hour before that, however, the City of Rock Falls was able to repair the transformer disconnect switch, restoring power to the control building.
"The air compressors controlling the dam are operating again as usual," Bolinski said.
The water levels began steadily rising around noon Monday, reaching six feet just after 10 p.m. As of 3 p.m. Tuesday, it measured just below 6.3 feet.
The Sinnissippi Dam, completed in 1907, controls water elevation in the Hennepin Canal. The Illinois DNR expected water levels would drop 8-12 inches lower than normal, but are expected to be returning to normal on Tuesday.
"Since there was an alarm and a problem with the backup generator, IDNR is contacting vendors to come and evaluate the generator," Bolinski said. "At this point in time, IDNR does not know what caused the generator to overheat and does not have a timeframe on when the generator will be repaired. With power being restored to the control building, IDNR does not anticipate any problems before repairs to the generator can be made."
IDNR says because the opening of the dam gates was caused by an unintentional power failure, it was not able to put out any notices about fluctuating water levels.
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