August 26, 2021

Cause of San Juan Generating Station cooling tower collapse remains unknown

Hannah Grover

The San Juan Generating Station is pictured Monday, April 19, 2021, in Waterflow.

While the cause of the collapse of a cooling tower at unit one of the San Juan Generating Station has not yet been identified, Public Service Company of New Mexico has provided the New Mexico Public Regulation Commission with some more information regarding the event.

Following the collapse, the PRC issued a notice of inquiry into the incident, which occurred in late June, and opened a docket. PNM filed a response to questions raised in the notice of inquiry on Aug. 16 and the commission discussed the response during the weekly meeting on Wednesday.

In its response, PNM stated that the cause of the collapse has not yet been identified. Initial inspections could not identify any obvious cause and investigations are continuing, including a structural analysis.

The last inspection of the cooling tower occurred in June 2020, about a year before it collapsed. The inspection found no structural concerns, according to PNM’s response.

PNM was able to continue providing service to customers during the time that unit one was out of commission and the utility stated to the PRC that rates will likely not be impacted.

Related: San Juan Generating Station taken offline after cooling tower collapse

The debris from the collapsed tower has been removed from the site and temporary cooling towers were installed to facilitate the return of unit one to operations, according to information PNM provided to the PRC.

The costs of cleanup and repairs, including the temporary cooling towers, are estimated to be about $11 million, however the majority will be covered by insurance. The deductible is $2 million, which is shared with Tucson Electric Power, another owner of the plant. Because of that, PNM will likely pay $1 million.

The commission unanimously chose to keep the docket open in the case to allow for more information to come in, including results of the structural analysis.

Related: PRC plans to open official inquiry into San Juan cooling tower collapse

Commissioner Theresa Becenti-Aguilar proposed leaving the docket open, stating that her main concern was not part of the questions submitted to PNM. 

“My concern involves the safety of the employees and how does PNM comply with the safety regulations when it comes to training employees on safety concerns,” she said.

Commission Chairman Stephen Fischmann also supported leaving the docket open until the results come in.

“Something went wrong that that thing collapsed and nobody knew, nobody had an inkling,” he said. “Rather than having to reopen a docket, maybe it’s better, as Commissioner Becenti-Aguilar suggests, let’s leave this one open, let that piece of information come in, and hopefully then we’ll have enough to do a final resolution.”

Commissioner Cynthia Hall said that it is important to get the results, highlighting that PNM states it had done all the required inspections and made all the required repairs prior to the incident.

“I get the idea that they didn’t think there was anything wrong with the building and yet it collapsed,” she said. “So it would really, I think, be important, to find out why.”

The collapse came about one year before PNM plans to end its operations at the coal-fired power plant.

Commissioner Joseph Maestas said he plans to compile additional questions. He said that some of the replacement resources for the San Juan Generating Station will be delayed in coming online, which may necessitate continued use of the plant after July 2022.

“Some folks out there that heard about this tower collapse might be thinking, is this premature deferred maintenance or even neglect,” he said.

Maestas said he wants to be assured that the plant is safe and that such an incident will not happen again.