The Nebraska Public Power District and Nebraska Dam Safety Program were ignorant to Spencer Dam’s hazard potential and risk posed by moving ice, an 8-month investigation found.
The Association of State Dam Safety Officials (ASDSO) found human error was a factor in the failure of Spencer Dam in north-central Nebraska on the morning of March 14, 2019, among other things.
Along with thousands of dollars in property damage to the area surrounding the Niobrara River, one man, Kenny Angel, 71, died in the aftermath of the dam’s failure, as his was body was never found, and he was declared dead in June 2019.
The 93-year-old dam, owned and operated by the Nebraska Public Power District (NPPD), contained an earthen dike and a series of concretes gates and a powerhouse. The Angel family property sat behind the dike and was washed away after the dam’s collapse.
The Nebraska Dam Safety Program, the dam oversight division of the Nebraska Department of Natural Resources (NDNR), regulated Spencer Dam. The safety program assigns four classifications for hazard potential, a measurement of potential consequences if a dam were to fail: minimal, low, significant and high. Since the 1970s, when NPPD purchased the dam, state inspectors considered Spencer Dam a “significant” hazard potential.
Mark Baker, a Colorado-based engineer, along with an ASDSO panel, found the dam worthy of a “high” classification. However, the NDNR defended the dam’s classification.
“Multiple engineers and organizations reviewed the classification of the dam and classified it anywhere from low to significant hazard,” wrote Tim Gokie, chief engineer of NDNR’s dam safety division, in an email to NET News.
According to Nebraska Dam Safety Program, a high-hazard dam is classified when loss of life is probable in the event of a failure. The Angel family property stood just one-third of a mile from the dike, but the Army Corps of Engineers and every other entity, which determined the dam’s hazard rating, did not consider the family property because of ambiguity in the language of state regulations, the report found.
NPPD maintains the hazard potential wasn’t the power district’s decision to make. Regardless, a high-hazard classification forces the dam owner to create an Emergency Action Plan under Nebraska Dam Safety Program regulations. Spencer Dam never received such a rating, nor a plan because of that.
Angel, whose family has sued in NPPD for the loss of life and property, was warned by NPPD operators early on the morning the dam failed, according to the report and NPPD. Two employees warned Angel as they learned the dam’s failure was inevitable and told him to evacuate. However, it appears, Angel never left.
The dam collapsed when large flows of ice rubble, called “ice runs,” collected early in the morning on the Niobrara River last March. A failure due to ice runs is not a common thing, as the ASDSO has no ice runs failures in the organization’s database of 380 failures. Another organization listed a single instance of an ice-run failure in 1976, the report said.
“It’s something [the ASDSO is] just learning about.” NPPD spokesman Mark Becker said of ice runs. “Again, even the corps engineers, as [the ASDSO] pointed out, do not have a way to deal with that themselves as part of their studies.”
The dam industry lacks knowledge surrounding ice runs, the report said, as the Army Corps of Engineers is the only entity with any literature on dealing with ice runs. This is a problem for any entity responsible for dams in cold, northern climates, not just NPPD.
Even though the dam industry lacks knowledge, Spencer Dam wasn’t a stranger to ice runs. Three times before the NPPD purchased the dam in the 1970s, ice damaged or failed the dam. In 1935, the dam failed, at least in part, when ice accumulated on the reservoir, but no damage downstream was reported. In 1960 and 1966, ice damaged, but did not breach, the dam, according the ASDSO’s findings.
The histories of dams can tell a remarkable story that, sometimes, highlight what make them vulnerable, Baker of the ASDSO said.
“My analogy is if you go to the doctor’s office, the doctor doesn’t take a look at your skin and pronounce you healthy,” Baker said. “He or she asks about your history of surgeries and what’s genetics or like what diseases your parents had.”
The panel of engineers found no evidence to suggest Spencer Dam was modified to solve ice runs, or solve related problems, Baker said.
“No one was asking the question: well, what about ice runs?” Baker said. “How is this dam going to perform in the spring when the ice comes down the river?”
However, Becker said the public utility, since it acquired the dam, has properly maintained it and the report’s findings back that up.
“We were constantly going above and beyond what the state inspectors would say,” Becker told NET News.
The catastrophic effects of ice runs on Spencer Dam will be studied by engineers and dam professionals for years to come, as the London-based International Journal on Hydropower and Dams is interested in publishing the dam safety report in an upcoming issue.
“It isn’t just the current dam owner and regulator that can be considered here and the failure of this dam,” Baker said. “This has a long history, and everybody’s been involved with the dam since that time.”