Incident Report: SCADA Water System Fails

Wednesday, July 14, 2010 @ 08:07 PM gHale


An electronic water-pump monitoring system failed to notify city workers of low water-storage levels, causing thousands of Lake Havasu City, Ariz., residents to wake up to dry taps in their homes this past Sunday.
After learning about the problem, 30 city water division workers began a manual manipulation of the pumps to restore the water system. Crewmen said it took eight or nine tries to fire the pumps back up.
Other crewmen monitored the restoration’s progress, while others went around the city to check fire hydrants and bleed air from empty water lines.
“The failure was between the water treatment plant and the water collection well, which is the primary water source for the entire (water) system,” said Butch Wood, utility supervisor for Lake Havasu City Public Works Department Water Division. “(The reason) has not been identified yet.”
Water services came back at 11:30 a.m. Sunday, but Wood said it would take about 24 hours for each of the storage tanks to reach their six- to eight-million gallon capacity.
The incident began after pumps stopped manipulating ground water into the 106-foot-deep primary collector tank sometime Saturday night or early Sunday. Once collected, the ground water funnels through a treatment process to rid it of naturally occurring toxins.
The purpose of the water treatment plant is to prepare water for 15 water-storage tanks located within the city’s four water zones.
The overall system linked up to a Supervisory Control and Data Acquisition (SCADA) system, which notifies on-call system operators when the pumps have failed or if water levels are low in the collection tank or storage tanks.
But for some unknown reason, the SCADA system did not alert personnel to the deficient water levels or pump failure alerts.
Brent Morris, water division production field supervisor, said the SCADA system alerts workers on a monthly basis but usually for small-scale issues. On a normal basis the 24-foot tall holding tanks fluctuate between 17- and 21-feet of water. When the water level hits 17 feet, it is on the low end. On Sunday morning, the SCADA system showed about 6 inches of water in the bottom of some of the water-storage tanks.



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