At 12:38 p.m. on Friday, Feb. 17, an intake valve froze at the Rocky Mountain Energy Center in Hudson. Enough electricity to power half a million homes vanished.
In less than a day, that failure was followed by others at 17 area power plants, compounded by mistaken forecasts and inadequate emergency planning. Finally, at 6:14 a.m. on the coldest morning of the year, an Xcel Energy manager declared at the end of an all-night battle, “There is no gas to be had.”
And with the temperature at minus 13 outside, Xcel turned off the heat in 82-year-old Dorothy Davies’ condo for four hours.
“The thing of it is, I have two fake hips and two fake knees. That metal, it gets so cold you feel like you’re freezing to death,” she said. “It was so cold your teeth were chattering.”
By the time the accidents and missteps concluded with Feb. 18’s unprecedented winter rolling blackout, Xcel had lost nearly half its power supply in 20 hours. About 325,000 Colorado electric customers were left shivering – most for just 30 minutes, but 20,000 of them, including Davies, for much longer.
A review of Xcel’s performance in the days leading up to the crisis indicates it could have been avoided. But inaccurate weather and power-demand forecasts left the company vulnerable to a series of unforeseen mechanical problems at power plants.
A lack of natural-gas storage made it im- possible for the company to meet the demand for steam to generate electricity.
Now the one-day emergency has energy experts asking whether Xcel’s operating subsidiary, Public Service Co. of Colorado, has enough gas supply and storage to avoid future and more catastrophic winter blackouts in a system designed to provide peak electricity in uncomfortable heat, not potentially deadly cold.
F. Lee Robinson, a gas trader who helped develop one of the independent power plants supplying Xcel’s Colorado system, sees a critical need for more natural-gas storage.
“Public Service’s system is very fragile. Public Service doesn’t have storage,” he said. “It’s extraordinary.”
Given adequate storage, this winter’s power crisis “would have been a nonevent,” he said. “Nobody would have known it happened.”
Xcel declined to comment for this story, citing an ongoing inquiry by Colorado’s Public Utilities Commission. The story was pieced together through documents Xcel provided to the PUC, interviews, and available forecast and energy records.
The events that led to the Feb. 18 shutdown have their roots in Xcel’s increasing reliance on natural-gas-fired boilers rather than coal to create steam and generate electricity. To serve 1.3 million Colorado electric customers, Xcel also has grown reliant on outside contractors for extra power generation on the hottest summer and coldest winter days.
Xcel and its outside contractors both turned to natural gas to meet that demand. Between 1993 and 2002, according to federal energy data, the generating capacity of Colorado gas plants grew nearly tenfold, from 262 megawatts to 2,370.
Yet Xcel closed one gas storage facility, which has not been replaced, as its gas use skyrocketed. Without more storage, the company must rely largely on the unpredictable natural-gas market for spot deliveries, putting a premium on the ability to accurately forecast demand from residential gas customers and the power plants.
By coincidence, one month before the blackouts, the PUC called additional gas storage “an important factor in reducing volatility” and encouraged “a proposal to provide additional storage.”
Now the commission staff is investigating why the winter blackout happened and how to prevent recurrences.
“The commission certainly is looking at whether the company had an adequate supply of gas to get through that day,” spokesman Terry Bote said, and “storage is one of the issues that the commission is addressing in this investigation.”
The investigative report could recommend storage, purchasing or procedural changes to minimize the risk of running short of gas and electricity in future winters. But Xcel cannot be penalized financially without further commission proceedings.
Bote said Xcel has not applied yet for additional gas storage. He declined to specify how much existing storage capacity the company had, calling that information confidential.
Faulty forecasting
As a mass of arctic air pushed into Montana on Feb. 15, Xcel’s meteorologist put together a company forecast for the upcoming Presidents Day weekend: overnight lows of 6 degrees for Friday the 17th and early Saturday the 18th.
Utilities such as Xcel generally work two or three days in advance of holiday weekends to secure electricity and natural gas for their customers because suppliers can be hard to reach.
Daily forecasts play into those scheduling decisions. The colder it is, the more gas and electricity get used.
“You can’t do anything in this business without thinking, ‘What is the weather going to be in a couple days?”‘ said Claudia Rapkoch, communications director for NorthWestern Energy, a utility that serves Montana.
Xcel operates its own power plants and also contracts with independent power producers for power. That electricity is delivered instantaneously over a network of transmission lines to customers.
Xcel buys its gas from production companies and ships it through giant pipelines to its power plants, independent producers and its Public Service Co. distribution system for use by its 1.2 million gas customers.
Bob Glancy, a meteorologist with the National Weather Service in Boulder, said on-the-mark forecasting is critical to utilities.
“They are making very expensive decisions on purchasing,” he said. “They can’t wait until 12 hours before a storm to make a decision.”
But as Xcel was making its energy generation and gas-buying decisions, it appears it was relying on faulty forecasts.
At 4 a.m. Thursday, a National Weather Service area forecast discussion for Denver called for temperatures between zero and 5 below Saturday.
Still, Xcel maintained a more optimistic forecast for a lowest possible temperature of 1 above zero going into Presidents Day weekend. On that basis, it decided Thursday that it had adequate electricity and natural gas to get through the cold snap.
Early Saturday, the temperature in Denver hit minus 13. Xcel’s forecast missed by 14 degrees.
“If I look at a forecast and I’m 10 degrees off, I’m not happy,” Glancy said. “If I’m 20 degrees off, I’m really not happy.”
In a report filed with the PUC on the rolling blackouts, Xcel defended its forecasting.
“Cold weather is not unusual in Colorado. Weather forecasts missing the cold weather are also not unusual in Colorado,” the company said.
And Xcel, which appears to have used an array of websites in creating its forecast, was not alone in its error. Local television forecasters, such as those at 9News and Channel 4, also missed the extreme cold, forecasting as late as Thursday evening that Saturday’s low would be either 10 or 8 degrees above zero.
By Friday afternoon, when the National Weather Service issued a warning of subzero Saturday temperatures, the mercury was already approaching zero in Denver, and Xcel’s problems had begun.
Limited supplies
The mishaps, which Xcel called “an unprecedented series of generation plant outages,” began the Friday afternoon before the holiday weekend.
Going into the weekend, Xcel expected a power supply of 7,600 megawatts. A megawatt equals 1 million watts, enough electricity for 800 to 1,000 homes. Half of Xcel’s power supply comes from its own plants, the rest from independent providers and other utilities.
The first sign that one frigid night could cripple Colorado’s power system came when freezing air filters at Rocky Mountain Energy Center, a new gas plant in Hudson owned by a California-based independent power producer, shut the plant down. Xcel called for replacement power from two Blue Spruce gas units in Aurora owned by the same operator, Calpine Corp. But at 3:18 p.m., valve problems tripped off the Blue Spruce turbines.
Those losses alone took out 900 megawatts, nearly half the power reserve Xcel projected for the weekend.
Kent Robertson, a Calpine spokesman, said prevailing winds blew water vapor accumulating outside Rocky Mountain Energy’s cooling tower into the air intake filters.
The vapor froze, “essentially starving the natural-gas turbines of the air they need to combust natural gas,” he said.
“The timing was also unfortunate,” he said. When the plant shut down, Calpine was installing heaters in air intakes “to prevent the freezing from occurring. We were literally in the middle of work with this scenario in mind.”
When Calpine tried to run both Blue Spruce units on gas, “we discovered the fuel supply valve had frozen up,” Robertson said. “We couldn’t load up the turbines.”
Other independently owned gas plants also supply power to Xcel from the Brush and Manchief stations in Morgan County. But according to Xcel’s report to the PUC, two Brush units were “unavailable (not in warm standby mode)” and the boiler was drained that day on a third unit because it was “not expected to run.”
Colorado Energy Management operates those units. Its president, Jim Nolan, said the two unavailable units had been shut off at the request of Xcel, which decided in December to save a modest amount of money daily by turning them off for the winter.
The third unit was running on a test basis earlier that day, Nolan said, and Xcel told plant operators to shut it down.
“That’s 130 megawatts. It would have been great to keep that on,” Nolan said. “We were doing everything we could to keep our end of the bargain up and keep our plants available.”
By 2:30 p.m. Friday, Xcel was aware that the gas-fired plants it owns or contracts with were burning more gas than expected. Its gas traders immediately began looking for more supply.
But supplies were limited.
“In reality, if you experienced an outage at 8 a.m. and called a gas trader at 8:30 a.m., he wouldn’t be able to get gas on the system until the next day if he didn’t have access to storage,” said Randy Curtis, a gas trader for Wasatch Energy.
“The best policy,” he said, “is have the right kind of (gas purchasing) contracts in place, watch the weather enough to know what to anticipate and have enough storage capacity.”
Colorado Interstate Gas, which operates transmission lines that feed Xcel’s system, gave approval for Xcel to pull extra gas off its pipeline.
But at 5:34 p.m. that Friday, with the temperature in Denver already below zero, CIG warned Xcel it might not be able to maintain pressure in its gas lines because demand was exceeding supply with the bitter cold. As homeowner furnaces ran wide open, gas-fired power plants found pressure dropping precipitously.
“I know that Colorado was caught off guard when it came to the cold snap,” said CIG spokesman Richard Wheatley. “We tried to move all available volumes of gas toward Colorado.”
Robinson, the gas trader, said that as the Front Range population mushroomed in the 1990s and as Xcel turned to independent producers that generate power with natural-gas Xcel supplies, the utility’s gas use outpaced its pipeline and storage capacity.
Xcel has a storage facility near Wiggins. But it won’t say how much gas that facility holds or whether most of that gas was exhausted by February.
A desperate hunt for gas
Independently owned Manchief station’s unit 11 was started in midafternoon Friday, and Xcel called for unit 12 to join it about 5:30 p.m.
Xcel also had started buying extra power from outside sources about 4 p.m. Friday – half an hour after the National Weather Service predicted a Saturday low of minus 9.
The Manchief station, near Brush, is especially valuable in a critical situation because it can draw gas directly from Xcel gas storage instead of pipelines.
Together, units 11 and 12 can add 300 megawatts to Xcel’s power supply, enough to replace the Blue Spruce units. But in extremely cold weather, plant manager Joe Keefe finds unit 11 easier to start.
“They’re sisters, but they’re not twins,” he said.
Unit 12 balked. Keefe, who was at dinner, went back out to the plant and tried a series of manual manipulations to push it to full power.
“Nothing worked,” he said. “We were stuck at 80 megawatts.”
At half power, it was also running in a mode that threatened to exceed air emissions standards. So Keefe shut it down until morning, when the air was warm enough to crank it up.
He and Nolan said unit 12 probably would have run at full power if the call to start it had come a little earlier.
“If it wasn’t that cold, I’m pretty sure it would have started OK,” Keefe said. “We didn’t know that, and Xcel didn’t either.”
Shortly before midnight, a steam boiler at Xcel’s Fort St. Vrain power plant went out, reducing the plant’s power output by 40 percent.
“Stuff was freezing up, and they were in a frenzy,” an Xcel dispatcher reported.
By early Saturday, a wrong guess about the overnight low temperature was causing three problems with gas supply: Extra gas was needed for heating. Extra gas was needed for electricity. And when highly efficient gas turbines at power plants failed, Xcel had to turn to less efficient units, which consume more gas to produce the same amount of power.
At 5:18 a.m. Saturday, the Thermo Cogeneration facility in Fort Lupton reported it was losing gas flow. In the next hour and a half, its output plunged 233 megawatts. At 6:14, Xcel’s Valmont 6 plant lost gas pressure: 53 more megawatts gone.
At Xcel, the graveyard shift launched a desperate effort to make it through the night. Gas control hunted in vain for gas. There was none available for the Tri-State Generation and Transmission Association plants in Brighton and Limon. There was no gas for Plains End. There was no gas for the Valmont 7 and 8 units. There was no gas for the Brush unit that was shut down Friday. There was no gas for Xcel’s own Zuni units. There was no gas to restart Rocky Mountain Energy Center, the largest independent plant in Xcel’s supply.
Tri-State spokesman Jim Van Someren said its plants were ready to run that Saturday morning with power dedicated by contract to Xcel. But “it is up to them to schedule the gas,” he said.
Containing the crisis
Xcel waited until 6:06 a.m. Saturday to order its interruptible gas customers to stop using gas. Interruptible customers get a price break in exchange for agreeing to stop using gas during an emergency.
Then it waited two more hours before ordering non-Xcel gas customers transporting gas on its pipelines to use only the amount of fuel they had contracted for.
By 6:14 a.m., 17 generating units, including the giant coal-fired Cherokee plant, had failed or could not start. A company dispatcher instructed electric traders to buy 600 megawatts of power at any price for delivery before 8 a.m. All gas power plants capable of burning fuel oil were ordered to make the switch.
At 6:37 a.m. Xcel began cutting power to its interruptible electric customers in an effort to maintain balance between the demand and the power being generated. But not all interruptible customers were dropped, and Xcel told the PUC that the emergency measure did not work as intended. The company has not explained why that happened.
Xcel also curtailed power sales to some, but not all, of its wholesale customers who agreed to interruptions in exchange for price breaks.
“Approximately 413 megawatts of long-term wholesale sales were taking place during the time of the controlled outages,” Xcel reported to the PUC.
Among the customers with interruptible contracts were the Western Area Power Administration, the Municipal Energy Association of Nebraska, the Arkansas River Power Authority and Aquila.
James “Rick” Gilliam, a senior energy policy adviser at Western Resource Advocates who worked for Public Service in the 1990s, questioned why Xcel was selling so much power on the wholesale market as it ordered rolling blackouts and why it missed interruptible customers.
“That’s the very reason they have interruptible customers,” he said. “It sounds like they had the right to interrupt some of these contracts, but they didn’t do it.”
At 7:16 a.m. Xcel’s systems operation center, in cooperation with the agency that oversees the Western power grid, declared a Level 1 energy emergency alert, and a request went out across the grid to send power to Colorado. The California independent system operator and others offered energy beginning at 7:39 a.m.
But when the Front Range power plant, an independent provider near Colorado Springs, went down because of frozen water valves at 8:40 a.m., Xcel could not get extra power fast enough. The company, which had expected to have 7,600 megawatts available, was now down to 4,400, 400 fewer than were needed to meet the demand and a required reserve.
At 8:48, in subzero temperatures, Xcel initiated rolling blackouts for 325,000 customers statewide in order to keep the crisis from spreading across the Western U.S. Those controlled outages lasted until 10:18 a.m, but problems resetting some distribution feeders left about 20,000 customers without power for up to four hours.
“Localized outages we can deal with. Cascading outages are something we don’t want to happen. We will cut off the hand to save the body,” said Frank McElvain, a manager with the Western Electricity Coordinating Council, which oversees the Western grid.
Blackouts unannounced
The rolling blackouts were unannounced.
In Westminster, Dorothy Davies donned a heavy robe, wrapped herself in a blanket and waited four hours for her electrically controlled gas furnace to start.
Her artificial hips and knees ached. She shivered in her blanket. Her two-bedroom condo was dark in daytime, so she used a flashlight to find her way around.
“I didn’t go anywhere” to escape the cold, she said. In the Spanish Oaks condos, “we’re older and we’re kind of confined. We were all freezing.”
Floyd Fahey, an 85-year-old Centennial resident, was at home that morning when his furnace shut off sometime after 9.
It was a bit of unwelcome deja vu.
Just weeks before, a mechanical problem with his gas furnace had kept him in the cold for two days while he waited for a replacement part to be shipped and installed.
“My daughter wanted me to come over there and stay, but I felt more comfortable here at home,” said Fahey, who uses a walker to get around.
So on Feb. 18, for the second time in a month, he bundled up and waited for his heater to come back on.
“For an 85-year-old man, I remember he had sweaters and blankets on. That’s a lot for an older person,” said his daughter Becky Kimbley, who lives across the street.
Across Colorado, more than 250,000 people called Xcel trying to find out what happened – and got a busy signal. Others remained on hold for 45 minutes, only to be told the duration of the outage was unpredictable.
Pam Moore, a nurse for Exempla Lutheran hospice, couldn’t get any answers and spent Saturday morning worrying about whether her in-home patients were freezing and scared and whether their oxygen supplies were working.
“They are close to death, and they don’t have a lot of fat on their bodies,” Moore said. They survived.
Susan Thomason debated whether to break a window to get into her Centennial house that day. She had left for a dog show just before the outage, carrying an electric garage door opener instead of keys.
“When we got in, it was 53 degrees in our house,” she said. “For them to say on the coldest day of the year they didn’t have enough gas? I would think they would have been prepared.”
Staff writer Steve McMillan can be reached at 303-820-1695 or smcmillan@denverpost.com.
Staff writer David Olinger can be reached at 303-820-1498 or dolinger@denverpost.com.
