Rebuilding work is nearly completed for several transmissions line destroyed by last June’s tornadoes that left more than 76,000 customers without power.
The June 16 storm was the fourth-worst in OPPD’s history in terms of customer outages, but was considered the worst ever in terms of damage to the transmission system, said Dannie Buelt, manager of Transmission Engineering. A total of 12 miles of transmission lines in Sarpy and Cass Counties were destroyed, including a seven-mile portion of a 20 mile, 345-kilovolt transmission line just south of the Omaha metro area. That voltage is the highest used by OPPD and the seven miles is the longest stretch of storm-damaged lines in the utility’s history.
In all, 106 poles along nine different lines were damaged in the storm.
“It became evident just how bad it was when line maintenance technicians drove the lines and saw it firsthand,” Buelt said. “We knew a major river crossing was down. That was our first indicator that it was pretty bad.”
Further assessments were completed by OPPD’s Asset Management and Maintenance Optimization Department using a helicopter that flew the whole route and the “H frame” structures all looked like “little explosions of wood.”
While much of the restoration work was done in the days and weeks following the storm, the seven-mile transmission line would take longer. Typically, a project this size would take two years, Buelt said. But OPPD and its customers would need the line back in service much sooner, before this summer, the peak demand season for electricity.
The deadline to finish the line was set for May 2018. To expedite the project, the line would be rebuilt using existing structure designs from a recent project ensuring the line met current construction standards for wind and ice. The new poles would also be steel rather than the previous wood.
“We made the decision it would be most beneficial for OPPD in the long term to rebuild the line using modern construction standards,” he said. “This is a more resilient design than the one it was replacing and will provide additional capacity as well.”
The work is being done by Timberline Construction of Rapid City, S.D. This portion of the overall storm effort will cost approximately $6 million and OPPD will be seeking partial reimbursement from the Federal Emergency Management Agency (FEMA) for damage related to the June 2017 storm.
As soon as the 345-kV line is rebuilt, a temporary structure on a Platte River crossing will be replaced, marking the end of the rebuild efforts from the storm. That is also expected to be done in May, Buelt said.
“Weather has been an issue for us,” Buelt said. “We are currently running a few weeks behind but are looking to make some time up with additional crews, longer work days and seven-day work weeks until it’s completed. This was a pretty extensive engineering effort for us to absorb in the middle of a full spring construction schedule.”
Buelt said it is uncommon for OPPD to experience storms that have such a profound impact to the transmission system. Lessons learned from the June 2017 storm are still being implemented.
Along with improving processes for storm response and reaction time, the storm provided a unique opportunity for OPPD to strengthen decision making processes associated with large transmission impacts and improve system resiliency as well, he said.