Elected officials homed in Tuesday on the timeline of events that led to an abrupt order of forced blackouts on Sunday in Louisiana, prompting Entergy and Cleco to cut the lights to 100,000 residents in the New Orleans area amid hot, late-spring temperatures.

Regulators had previously pinned the outages, in part, on the unexpected shutdown of River Bend, a nuclear plant north of Baton Rouge. But Entergy and federal officials said Tuesday that River Bend was shut down because of a leak on May 21. That left the grid operator, the Midcontinent Independent System Operator, or MISO, with several days to plan for the lower supply of electricity.

The timing has raised more questions about why Louisiana was forced into a “load shed” event that caused widespread outages well before peak summer demand for electricity.

Officials are asking Entergy and MISO officials to answer questions publicly about what happened next Tuesday at a City Council meeting and at a Public Service Commission hearing next month, in a bid to figure out how the looming power deficit was not caught earlier. Entergy is also expected to face questions about its long-standing lack of transmission in south Louisiana that has created “load pockets” where it’s difficult to import power.

The River Bend nuclear plant shut down May 21 after operators noticed a leak, which they identified two days later as the result of a faulty valve in the reactor’s cooling system, according to the Nuclear Regulatory Commission. Entergy fixed the valve over the weekend before bringing the plant back online Monday.

The plant did not unexpectedly trip offline over the weekend, as has been previously reported, said Victor Dricks, spokesperson for the NRC.

But the Mid-Continent System Operator, a nonprofit that operates the electric grid across a wide swath of the U.S., did not give Entergy or Cleco advance warning that power demand was set to outstrip supply. A New Orleans City Council member said Tuesday that Entergy reported getting only three minutes notice Sunday before being forced to “shed load,” or proactively turn off the lights for tens of thousands of people to avoid catastrophic damage to the electric grid.

If regulators and Entergy had known about the looming power deficit, regulators and advocates say they could have taken steps to prevent forced blackouts. Some industrial plants have contracts that require them to ramp down power during such emergencies, allowing the utility to free up 280 megawatts of capacity in the Entergy system as of 2023. Other customers also could have been required to conserve energy.

Two days after the outages, it remains unclear how other factors might have been at play. Higher than forecast temperatures could have contributed, but Logan Burke, head of the Alliance for Affordable Energy, noted that Entergy and Cleco were required to shed 600 megawatts of power, a huge amount that makes it unlikely bad weather forecasts can totally explain it.

“The question is, what else do we not know about?” Burke said, noting it’s unknown whether non-nuclear power plants or transmission lines were out of service during the event.

“I can imagine MISO missing 100 megawatts,” Burke added. “600 is just hard to fathom where that’s coming from.”

MISO said that “unplanned” outages of generators and transmission structures contributed to the power losses. But neither MISO, nor Entergy and Cleco, have provided more information about which generators and transmission lines were down.

A MISO communication shared with The Times-Picayune shows the grid operator was aware of a “planned outage,” then another unit went down, though the communication does not specify which units. Entergy had a separate nuclear plant, Waterford, that was down for scheduled maintenance, which is normal in the spring.

“Operating conditions over the weekend required us to take our absolute last resort action to maintain reliability in our South Region — a temporary, controlled load shed,” MISO spokesperson Brandon Morris said Tuesday. “We will conduct a thorough assessment of the event and provide additional information once complete.”

Entergy had taken its Waterford plant down for scheduled maintenance well ahead of the event so it could fix it up ahead of peak summer demand, spokesperson Brandon Scardigli. He said Entergy had been monitoring warmer than usual temperatures, but its own models did not show the need for load shedding. He said MISO uses a different model with a broader view of system conditions.

And while River Bend was offline, he said Entergy made that outage known to MISO for its modeling several days before.

“While the River Bend generating unit was offline during the event, it had been out for several days before the event, and its outage was accounted for in the generation that Entergy Louisiana and Entergy New Orleans made available to MISO and in MISO’s own modeling,” Scardigli said.

‘Forecasting was off’

Federal energy regulators began encouraging the creation of grid operators like MISO decades ago as a way to make sure the market for wholesale electricity was fair and reliable. MISO was formed as a nonprofit in the late 90s and has grown to operate the grid — and wholesale electric markets — across a wide swath of middle America.

In 2013, under pressure from the U.S. Department of Justice amid its investigation into alleged anticompetitive practices, Entergy joined MISO, creating a new region called MISO South.

Employees in a cavernous facility in Carmel, Indiana, MISO’s headquarters, sit in front of a huge array of screens showing information about the electric grid in its territory. They plan for which power plants dispatch power onto the grid to make sure electricity flows smoothly and at the right levels.

Another grid operator, the Southwest Power Pool, was doing similar work last month when operators identified “instability” on the grid and ordered SWEPCO to shed power, causing blackouts for 30,000 people in the Shreveport area.

Public Service Commissioner Eric Skrmetta, a Republican who is one of five statewide utility regulators in Louisiana, has long opposed Entergy’s participation in MISO, arguing the utility could get a better deal elsewhere.

Skrmetta said he believes there was enough power and transmission in the region when MISO ordered the load shed over the weekend. He said MISO should have known ahead of time that River Bend was down.

“They plan it a day ahead, two days ahead,” Skrmetta said. “There’s absolutely no reason for MISO to call this unless MISO made a mistake.”

Commissioner Davante Lewis, a Democrat representing New Orleans, said he was initially told a plant unexpectedly went offline, leading him to believe River Bend tripping offline was the source of the problem. After NRC’s confirmation that River Bend went down much earlier, Lewis said a “misforecast” along with generators and transmission lines being out appears to be the root of the problem.

Lewis said he remains concerned about how Entergy’s inability to import power using long-range transmission might have played a part.

“The forecasting was off somewhere,” he said.

Councilmember JP Morrell, chair of the City Council’s utility committee, said he expects to get answers from MISO and Entergy during their meeting next week.

Morrell said he’s particularly concerned about the lack of advanced warning from MISO that demand was outstripping supply, as well as who decided which parts of Entergy’s territory would have the lights turned off.

“If we knew as early as Wednesday of last week that generation was gonna be a problem, it would have given regulators the ability to … curb demand to avoid the brownout,” Morrell said.

He added that while Louisiana is not yet in summer peak electricity demand, lots of power companies do their maintenance this time of year, which can cause supply issues.

Long-standing issues

Entergy has long had issues with some of its nuclear plants, including Grand Gulf, the source of years of litigation over alleged mismanagement. A report by the Union of Concerned Scientists published Tuesday found River Bend was the most problematic nuclear plant in the U.S., when measuring regulatory violations.

Entergy told the NRC, which oversees nuclear plants, that it noticed an unidentified leak in River Bend’s cooling system last week. Nuclear plants have a series of pipes circulating water to cool down the reactor. Entergy identified a faulty valve in one of those systems, and the leak reached a threshold — two gallons per minute over a 24-hour period — that required operators to shut the plant down and fix it.

Entergy welded the valve over the weekend and brought the plant back online Monday. As of Tuesday morning, it was operating at 80% capacity, Dricks said.

Energy advocates in recent days pointed to a long-standing lack of transmission as a potential part of the problem, too. Transmission lines can carry power long distances, but a lack of Entergy lines in south Louisiana creates what experts call “load pockets,” where it’s difficult to import electricity.

Over the weekend, prices for electricity soared in south Louisiana, according to MISO data, while prices in nearby states were low, underscoring Entergy’s lack of ability to import electricity from elsewhere.

Regulators have scrutinized Entergy’s lack of transmission lines in the past. Staff of the Public Service Commission noted that Entergy failed to explore new transmission options in its most recent long-range planning process. Staff said in a 2023 report that utilities in other states evaluate transmission lines as a way to bring more capacity into an area, but Entergy doesn’t unless it’s tied to a specific power plant.

Lewis said Tuesday that Entergy’s lack of transmission remains a problem.

“This is partly why I voted against Entergy’s (plans),” he said. “They completely ignored transmission build up.”