At 2 p.m. Tuesday, a power transmission line near Spokane overheated. Without a drastic reduction in power being carried by the line, there was fear that circuit breakers would trip on a major Northwest power intertie.

The Bonneville Power Administration immediately ordered Seattle City Light to reduce output at its Boundary Dam project. Within two hours, output at Boundary was dropped by 600 megawatts.

The city -- all of its businesses and all of its homes -- was using only 1,000 megawatts that day.

Other Dam Fired Up

Seattle was able to replace the power by firing up Ross Dam on the West side of the Cascades, which uses different transmission lines.

There were no power outages, but the city was forced to use water behind Ross Dam that it was holding in reserve for this fall.

The BPA order, City Light officials say, had a potentially major dollar impact. They're still calculating the exact amount, but output was reduced at Boundary for six hours.

'Reaching Their Capacity'

Power managers tell KOMO 4 News the close call Tuesday clearly show the danger of transmission problems and blackouts this winter.

"Certainly if we have cold winter days, Bonneville is telling us that the lines are reaching their capacity," said Paula Green, Seattle City Light deputy superintendent and power manager.

Green says there's no easy way to increase transmission capacity and that the incident has increased concern about the sufficiency of the Northwest power grid.

She says the answer may be creating power generation near cities and near big power users. Seattle City Light, she says, is considering building a 250-megawatt, natural-gas-fired generator on the Duwamish.