That new $165 million water plant in DeKalb County will cost ratepayers another $180,076.

County commissioners on Tuesday authorized the additional expense to prop up a high-tech backup power system at the Scott Candler Water Treatment Facility that keeps failing during storms.

Water faucets across half the county sputtered on a Sunday morning in June when a storm knocked out power to the plant, and the backup generators failed to fire. Then, last month, an outage dropped water pressure enough to trigger a boil water advisory across two-thirds of the county.

Residents had to boil their drinking water during a two-day period. It was more than an inconvenience for water-dependent businesses, which spent untold dollars coping. Restaurants had to buy ice and bottled drinks, since their ice machines and soda fountains rely on tap water. And grocery stores had to chuck produce moistened by automatic misters.

The late-night outage on July 22 idled the new Scott Candler plant near Doraville that became operational last year. It was billed as a high-tech facility that met "high standards for reliability and risk-based redundancy," yet Mother Nature wasted little time humbling it.

The latest outage led the county's watershed management department to seek a Band-Aid for the plant. Officials asked for money to rent a diesel-driven pump to prevent further storm-related disruptions.

Department director Francis Kung'u told commissioners Tuesday that the pump, which will be rented from a Marietta company, will serve as a temporary backup. Workers can turn on the diesel generator before a storm and during tests of the permanent system that will be designed to replace it, Kung'u said.

He said the plant's computerized backup system failed because of faulty software. "We realized there was a defect in the computer logic control," he told commissioners.

Commissioner Kathie Gannon asked if the diesel generator would prevent further "blips in the power," and Kung'u said it would.