Report: Spencer Dam Owners, Regulators Were "Ignorant" of Ice Risk

April 21, 2020, 1:32 p.m. ·

Spencer Dam (Photo: NEMA)

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The Nebraska Public Power District and the Nebraska Dam Safety Program were ignorant of the risk of ice runs and hazard potential of the Spencer Dam’s failure, an eight-month investigation found.

The Spencer Dam broke apart early on the morning of March 14, 2019, when large amounts of ice collected in the Niobrara River. Human error was also a factor, according to the 128-page report released Tuesday by the Association of State Dam Safety Officials:

  • The dam’s owners and state regulators underestimated the potential for a life-threatening flood.
  • Even though the dam had a history of being damaged by ice, there was a “notable lack of knowledge” about the potential for damage caused by ice accumulations.

Spencer Dam in 2009 (Courtesy Straw Bale Saloon)

Spencer Dam, March 2019 (Photo: NEMA)

As the “bomb cyclone” moved across the region, multiple layers of broken ice, known as an ice run, flowed down the Niobrara River the night before. Chunks of ice clogged gates, causing the dam's failure.

The report concluded nothing more could have been done by NPPD operators on-site to prevent the failure. However, the panel of dam safety experts said if power district, which owned the structure, and state regulators had "better understood the potential hazards to and from the dam, the risks could have been mitigated." Dam safety is regulated at the state level by the Nebraska Department of Natural Resources (NDNR).

The Nebraska Dam Safety Program (NebDSP), assigns four classifications for hazard potential; a measurement of the risk of a potential collapses: minimal, low, significant, and high. Since the 1970s, when NPPD purchased the Spencer Dam, state inspectors considered it a "significant" hazard potential.

The ASDSO panel of engineers felt Spencer Dam deserved a high-risk designation under the state's definition, meaning a loss of life is probable in the event of a failure. Labeling the dam as high-risk would have required NPPD to develop an Emergency Action Plan identifying who downstream would be at risk and consider how to reduce damage in case of an incident.

In response to questions submitted by NET News, NDNR Chief Engineer Tim Gokie defended the dam's previous hazard classifications.

"Multiple engineers and organizations reviewed the classification of the dam and classified it anywhere from low to significant hazard," wrote Gokie.

After repeated inspections since the 1970s, Gokie said NDNR felt it could not justify changing the hazard potential set initially by the Army Corp of Engineers.

The report faults the owners and regulators for underestimating the potential of the dam to cause life-threatening flooding. Kenny Angel stayed on family property one-third of mile from the dam the night of collapse, even though NPPD operators warned him of the collapse, according to the report. His body was never found, and the Niobrara River erased all traces of the home and bar owned by the Angels.

The 93-year-old dam wasn't a stranger to ice damage, according to ASDSO's findings. In 1935, the dam failed, at least in part, when ice accumulated on the reservoir. No damage downstream was reported. In 1960 and 1966, ice damaged, but did not breach, the Spencer Dam.

There are lessons to be learned from the unique set of events along the Niobrara River. The dam industry lacks knowledge about handling ice-run related failures. The ASDSO panel concluded, “current dam safety best practices do not include evaluating dams for stability during ice runs.”

The dam safety experts acknowledged this was a unique event, noting, in the group's database of 380 dam failures, no dam failed during an ice run. Another organization listed a single instance of failure because of an ice run in 1976.

"It is difficult to say it was foreseeable," Gokie wrote, "when the dam industry has never considered, before Spencer (Dam's failure), that ice runs could fail a dam."

When reached for a comment on this story, the NPPD said its staff is reviewing the report and will comment at a later date. Power district officials told the Omaha World-Herald last year they felt the dam was safe, and the collapse was due to unprecedented events.