Tracking down the exact circumstances that set off the worst disruption of natural-gas service New Mexico has experienced in three decades — leaving close to 25,000 customers without gas Thursday and Friday during freezing weather — will take some digging.

Finding the answers could help prevent the situation from happening again, state Public Regulation Commissioner Jason Marks said Friday. He wants a full investigation into what happened, "not as a finger-pointing exercise, but to get things in place so if we face these conditions in the future, we don't have the same problems."

The Legislature also wants a report and will hear from the PRC and New Mexico Gas Co. at a hearing before the House Energy, Mineral and Natural Resources committee on Monday.

Marks said New Mexico Gas had a plan for curtailing customers' service if gas pressures dropped, and was implementing it, but couldn't keep ahead of the crisis as it unfolded Thursday.

The utility reported early Friday that natural-gas supplies were becoming stable. In Southern New Mexico, natural gas to Silver City and most of Alamogordo had been restored. In the northern part of the state, field crews were expected to work through the weekend to get gas back on for residents between Española and Red River.

Restoring service

Workers have to go house-to-house to turn meters off, bleed gas lines to make sure there is no air trapped in them, repressurize the pipes and then go house-to-house again to turn meters on and check pilot lights, according to Deborah Brunt, director of engineering for New Mexico Gas. She said crews from other states, other New Mexico municipal utilities and contracted plumbers are all helping New Mexico Gas crews handle the situation.

In Española, Ohkay Owingeh, and the Santa Clara and San Ildefonso pueblos, relighting work was expected to start Sunday and continue through Monday.

Gov. Susana Martinez on Thursday declared a statewide state of emergency.

More snow was forecast for today and early next week, though warmer temperatures were expected. National Weather Service senior forecaster Tim Shy said the Santa Fe area can expect up to an inch of snow in town tonight.

Many state offices and schools in Santa Fe remained closed Friday to reduce demand on natural-gas supplies. Santa Fe Trails bus service was suspended Friday but expected to resume today.

Sources of the problem

A perfect set of bad circumstances led to the crisis.

New Mexico Gas had plenty of natural gas in a Texas storage facility just on the other side of the Eastern New Mexico border, according to Brunt, who has 25 years in the industry. She said computer models use predicted weather conditions and customer demand to calculate how much gas will be needed so the company can purchase the gas ahead of time.

"We had scheduled and purchased more gas, 25 percent more than the model predicted, but it still wasn't enough," Brunt said, to keep up with the spike in demand as the temperatures dropped to record lows Wednesday and Thursday.

Rolling blackouts in the El Paso Electric Service area, which powers parts of Southern New Mexico including Las Cruces, added to the problem. Brunt said the blackouts affected two compressors in Chaparral, which affected natural-gas deliveries to the Alamogordo area.

Richard Fleager, El Paso Electric senior vice president, said the blackouts lasted 30 minutes to an hour, and he wasn't aware of it causing problems for any compressor stations. "We don't have enough information to be able to be of much help," he told a reporter Friday.

Brunt also said rolling blackouts prevented New Mexico Gas from accessing the substantial supply it had stored along the Texas border.

New Mexico Gas buys all of its natural gas from producers in the San Juan Basin in northwestern New Mexico and from the Permian Basin, which encompasses parts of West Texas and southeastern New Mexico. But once the gas is pulled from the ground, it is shipped to a processing plant and joins natural gas shipped through a huge interstate pipeline owned by El Paso Natural Gas.

Compressor stations all along the pipeline keep the gas pressurized, so it can be forced through the line to customers. Other compressor stations may have been affected by rolling blackouts in the rest of Texas served by the Electric Reliability Council of Texas grid.

Cold front in three states

A major cold front hit Texas, New Mexico and Arizona all at the same time. It was so cold it froze some of the natural-gas well heads and played havoc with some of the electric power stations. Demand rose in Texas, adding to the power drain and the rolling blackouts. Demand for natural gas rose in New Mexico and Arizona — for residents, businesses and utilities — tapping out supplies faster than they could be replenished.

New Mexico was not the only area left without natural gas. An estimated 14,000 Southwest Gas customers in southern Arizona also were without natural gas Thursday and part of Friday.

Richard Wheatley, a spokesman for El Paso Corp., wasn't available for comment Friday after hours, but earlier in media reports he confirmed that the sub-zero temperatures, high demand and power outages had contributed to reduced supply all along the pipeline.

Early warnings

Natural-gas managers knew there would be a potential strain on supplies as early as Tuesday. Early Thursday, El Paso Natural Gas was issuing notices warning of critical conditions and that some suppliers were pulling more natural gas off the pipeline than they had purchased. At 9:51 p.m. Thursday, the company issued a "force majeure" notice saying that demand on the system was significantly more than scheduled, a circumstance beyond the company's control. A force majeure is a legal term meaning "greater force," which exempts a company from some liability in the case of "acts of God," war or the failure of third parties to fulfill their contracts.

New Mexico Gas has a "curtailment plan," known as Rule 21 from the state Public Regulation Commission, that lays out how the company will reduce natural gas in case of interruptions and who will be turned off in emergencies. The last to be turned off are supposed to be residences and health care facilities.

Brunt said New Mexico Gas was aware of the potential supply problem and had already been talking to larger customers Tuesday, warning them of the huge cold front coming. At 1:30 a.m. Wednesday, they were alerted to the rolling blackouts by El Paso Electric. They asked commercial customers to switch to other fuels or reduce use and began shutting off gas to The University of New Mexico, Kirtland Air Force Base and a large cement plant in Albuquerque.

But no one was prepared for what followed. Pressure in the system declined steadily Thursday. "The loss of supply was huge," Brunt said.

Brunt said the last time a large-scale interruption of gas occurred was the winter of 1971, when there was another record-breaking cold spell.

Contact Staci Matlock at 986-3055 or smatlock@sfnewmexican.com. Reporter Kate Nash contributed to this story.

IF YOU GO

What: The House Energy and Natural Resources Committee will hear from state utility regulators and the New Mexico Gas Co. on causes of the natural-gas shortage and efforts to restore supplies.

When: 8 a.m. Monday

Where: Room 315 of the state Capitol