Courtesy graphic edited by Coly McCauley This map shows the two power lines leading into the Wood River Valley, as well as the approximate areas of where the transmission line failures took place on Dec. 24 (circles).
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Idaho Power Co. representatives on Tuesday added new details to a description of events that led to a prolonged power outage in the Wood River Valley that lasted from Christmas Eve through a good portion of the following day. They also emphasized the importance of adding redundancy to the single line serving Ketchum and Sun Valley.
At a Blaine County Commission meeting at the Old County Courthouse in Hailey, Idaho Power's Vern Porter, vice president of engineering and operations, and Brian Hobson, senior planning engineer, described the events that transpired over the holiday.
About 50 members of the public were on hand to hear Hobson explain that both of the power lines that provide electricity to the valley failed on Dec. 24 due to a combination of ice, freezing temperatures and high power demand. He also said the incident highlighted the need to begin implementing the proposed Wood River Electrical Plan, which would provide additional transmission lines, increasing the capacity and reliability of the system.
Currently, the valley is served by two transmission lines that merge at Hailey. The more powerful of the two is the Midpoint-Wood River line starting south of Shoshone and linking to Hailey via Carey, Picabo and Gannett.
The second is the King-Wood River line, starting near Hagerman and connecting to Hailey by way of Gooding and the western part of the Bellevue Triangle.
North from Hailey, only one line serves Ketchum and Sun Valley.
On Christmas Eve, the Midpoint line was the first to go at 9:50 p.m. Hobson said thick ice coating the line caused a circuit breaker near Picabo to open, de-energizing the line and causing power outages to Richfield, Carey and Hailey.
The system automatically shifted the power demands to the weaker King line, just about doubling its load, and causing that line to fail as well. Hobson said the failure on the King line took place near U.S. Highway 20 about 18 miles east of Fairfield at a point where the line had been spliced together.
When this second line failed at 10:25 p.m., there was no more electricity flowing into the valley.
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One of the most common concerns for residents was the time it took to restore power, as some homes did not receive power until 1 a.m. on Dec. 26.
Hobson said the delay was in part caused by difficulties in locating the problems on both lines, a process hampered by dense fog, snow and cold weather.
Idaho Power Foreman Cary Darling said the fog was so thick that employees needed to use GPS devices to locate substations and that the associated snowstorm hampered the use of trucks to inspect the lines.
The following day, a helicopter was employed to help in the search.
Even though the Midpoint line was working again at 10:15 a.m. on Christmas Day, a little more than 12 hours after it went down, power still couldn't be fully restored to all 17,000 customers in the region until both lines were up and running.
Repairs were completed by 3:30 p.m., but the return of electricity was delayed due to the distribution system.
Hobson said the "cold load pickup," when water heaters, appliances and other electrical devices switch on at once after a prolonged power outage, increases the demand for power by three to four times the normal amount.
Because of that, power had to be returned throughout segments of the system to prevent an overload and another outage.
Further delays were caused by car accidents that involved power poles.
More than 60 Idaho Power employees were working throughout the valley to get the power restored.
Construction of a second power line running from Hailey to Ketchum and Sun Valley was proposed in a Wood River Electrical Plan created by Idaho Power and a community advisory committee in 2007. Though a second line would not have prevented the recent outage, it's seen as important to decrease risk.
The plan, which outlines needed improvements and additions to the high-voltage transmission and substation infrastructure to address the long-term needs of Blaine County, also includes a third line beginning north of Shoshone. This line would split into a pair of lines as it heads north and would help provide additional capacity to combat a similar situation to that which occurred last month.
Hobson said Idaho Power would likely be before the commission sometime this spring as part of a public permitting process for the Hailey-to-Ketchum line.
Though he said he could not give a timeline for the southern line, the plan calls for the two new lines to be installed within the next five years.
Karen McCall, an advocate for renewable energy resources through Ketchum-based Dynamic Energy Systems Institute, said Idaho Power should prioritize the southern line so as to prevent such an event from happening again.
Porter said Idaho Power is ready to put its plan into action, but will require the support of both the community and its elected officials.
"Redundancy and reliability are necessary for the safety and economic viability of the valley," Porter said at the end of the presentation.
Jon Duval: jduval@mtexpress.com
