Just prior to an explosion that killed six workers and injured 27 at a Kleen Energy power plant in Middletown, Conn., earlier this month, a huge amount of natural gas was vented out of doors, but into a “congested area” between buildings.
About 400,000 cubic feet of gas – enough to fill a pro-basketball arena floor to ceiling with an explosive mixture – was vented amid vigorous construction activity at the new power plant, federal investigators reported at a news conference Thursday morning. Several “potential ignition sources,” including welding, were present in the surrounding area, they said.
On the morning of the Feb. 7, multiple pipe-cleaning efforts called “gas blows” sent natural gas surging through piping at 650 pounds per square inch and then outside through open pipe ends less than 20 feet off the ground. But, the investigators said, the congested area “likely slowed dispersion of the gas,” which collected and was ignited by an “undetermined” ignition source.
The key problem was not ignition sources, which are widespread at construction sites, but the common practice of venting of large amounts of gas from pipe cleaning into buildings or even outside. Insufficient attention was paid to this activity, which the investigators called “inherently unsafe.”
The safety issues raised by this accident are not limited to Connecticut [or] any particular company, facility, or individual,” Don Holmstrom, lead investigator for the US Chemical Safety Board (CSB), told reporters. With thousands of workers involved in building natural gas power plants nationwide, “the safety of these workers and the nation’s energy independence are at stake.”
There are 84 gas-fired turbines in 35 different plants that are either being tested or are still under construction, according to the Edison Electric Institute. A study by the Interstate Gas Association of America Foundation (INGAA) estimates that as many as 62,000 miles of new pipelines could be built in the next 20 years.
According to the CSB, purging of natural gas pipelines is a common occurrence as utilities and other businesses prepare to begin using natural gas or decommission a pipeline.
A key focus of the CSB investigation is to determine which codes, practices, or regulations might apply to such gas blows. Meanwhile, safety board investigators “strongly caution natural gas power plants and other industries against the venting of high-pressure natural gas in or near work sites,” Mr. Holmstrom said.
In at least seven incidents since 1997, workers have died and large-scale damage has been done to buildings as a result of pipelines being purged in an enclosed area, according to a CSB database, a spokesman told the Monitor.
Only three days before the accident, the CSB had recommended changes to the National Fuel Gas Code to prevent just such explosions involving gas purging. Yesterday, at a meeting in San Francisco, the National Fire Protection Association, which oversees the fuel gas code, voted to proceed with CSB recommendations to make gas-purging practices safer at construction sites nationwide.
While lauding that move, Holmstrom acknowledged that the type of purging identified in the gas code is different from gas blows used in the power industry – and that “power plants remain exempt” from the national fuel gas code.
Even so, he said, “companies must ensure that flammable gases are not vented into close proximity with ignition sources and workers. That is a vital safety message from all these tragedies.”
Amid increased scrutiny of the issue, Congress is expected to hold hearings on the possibility of setting a national standard for venting flammable gases at work sites.
Meanwhile, back in Middletown, police investigators obtained a search warrant to remove a memory chip from a hand-held gas detector in order to determine whether it contained data, according to the Hartford Courant. The application for a warrant could indicate that police are contemplating manslaughter or other criminal charges in the case, the newspaper reported.