The incident is a pointed example of the gap in pipeline safety rules as the industry continues its rapid expansion in the Marcellus Shale fields of Pennsylvania.
An Inquirer series last year found that this gap, coupled with a slow response from Pennsylvania, meant that hundreds of miles of high-pressure pipelines had been built with no safety oversight. Up to 25,000 miles could be built, experts say.
The state Department of Environmental Protection, which issued an air-quality permit for the station, is conducting its own investigation into whether the owners, Williams Partners of Tulsa, Okla., committed any violations.
But DEP typically enforces emissions standards for compressor stations, not gas safety regulations.
The agency last week says it told Williams not to restart the compressor without its permission. But the company began running it anyway a day or two later.
Helen Humphreys, a Williams spokeswoman, said the station's safety equipment functioned the way it was supposed to, isolating the gas release to the building itself. She called the dispute over the restart a "misunderstanding."
Earlier this year, the PUC began the job of enforcing federal safety rules for the pipeline systems being built to serve the thousands of new Marcellus wells.
But none of the rules applies when the pipes or compressors are in the most rural areas, known as Class 1.
For decades, the gas industry has fought hard to protect that exemption, defeating repeated attempts by Congress and safety advocates to change it.
PUC Chairman Robert Powelson and the head of the federal Pipeline and Hazardous Materials Safety Administration, Cynthia L. Quarterman, have spoken out for extending safety regulations to rural areas. Federal regulators are once again considering new rules. In Pennsylvania, State Sen. Lisa Baker (R., Luzerne) says she is preparing a measure that would have the PUC oversee all natural gas pipelines, even in rural areas.
Powelson said last year that "those citizens in those areas are saying, 'We want regulation.' We heard them loud and clear."
Williams' Lathrop station is in Class 1, but just off a two-lane highway in Springville, in Susquehanna County northwest of Scranton. About 80 wells owned by Cabot Oil & Gas feed into the 25-foot-high building.
It's not far from Dimock, where residents and Cabot have clashed over whether gas drilling polluted their wells.
One night last week, three newly drilled wells in the area were burning off gas in giant flares, residents said.
Williams, one of the largest gas producers in the country, purchased the station from Cabot in December 2010. Inside, seven giant engines that can run at more than 2,000 horsepower process about 365 million cubic feet of gas per day.
The day of the blast, gas built up inside the compressor building when an employee apparently left a valve open during maintenance work, said Colleen Connolly, a spokeswoman for the DEP's northeast region.
An emergency alarm sounded, which shut off the pipes running to and from the station. Workers got out.
Several minutes later, the gas exploded, ripping open the sheet-metal roof and upper walls of the structure, damaging one of the compressor engines, and touching off a fire that burned for several hours. No one was hurt.
"It sounded like a dynamite boom," said Paul Karpich, who lives less than a quarter mile away.
Connolly said the DEP asked Williams that day or the next to keep the facility shut down until the agency had a chance to get an engineer to inspect it. But the company restarted the station over the weekend without notifying the DEP, she said.
"We told them we weren't happy," Connolly said. "Their response was, It wasn't clear. We were very clear."
Connolly said the agency had not determined whether to fine Williams.
"We do have some authority over this, as far as assessing fines and whether they're able to keep operating," she said.
Connolly said Williams had applied for permits to build three more compressor stations nearby.
Humphreys said that the structure hit by the explosion was still sound and that six of the seven engines were back operating. Williams has promised to provide a report on the incident to the DEP, she said.
Duane Wood, a Springville Township supervisor, said he thought the company's response was "awesome." The next day, Williams' top executives flew in to meet with him and other local officials. They explained that the building was designed to vent the blast up and out, he said.
"It mushroomed," he said. "It did exactly what it was supposed to."
Two sizable pipelines run from the compressor station and feed into interstate transmission lines. One of them runs 33 miles south, to Dallas Township in Luzerne County, where residents fought a long, bitter, and ultimately unsuccessful campaign to stop it.
That Williams pipeline, like many of the new gathering lines that connect the shale wells, is 24 inches in diameter and designed to operate at 1,440 pounds of pressure per square inch - higher than many of the interstate transmission lines that are subject to more regulations.
Duke Barrett, a member of the Gas Drilling Awareness Coalition, said Williams and other gas companies repeatedly promised residents that their equipment posed no danger.
When another company wanted to put a compressor station next to a school complex, residents were told, "Everything would be safe and the odds of anything happening were very small," Barrett said.
"My thing is, it's all safe until it kills you," Barrett said. "There's no undo switch on a lot of this."
Karpich, who lives close to the Lathrop compressor station, said he was unhappy when Williams restarted the station so soon.
"I'm not really against them," said Karpich, who himself has a Cabot gas lease. "Just follow the rules and regulations. But there doesn't seem to be a lot of regulations right now."
Contact Joseph Tanfani
at 215-854-2684 or at firstname.lastname@example.org.
Staff writer Craig R. McCoy contributed to this article.