A report issued today by the US National Transportation Safety Board
blamed severe corrosion as the cause of the pipeline explosion in
New Mexico that claimed the lives of twelve people, including five children.

Below is an extract from the report.

Washington, D.C. - In a report adopted today, The NTSB determined that the
cause of a pipeline rupture in Carlsbad, New Mexico was the significant
reduction in pipe wall thickness and severe internal corrosion due to El Paso
Natural Gas Company's (EPNG) failure to prevent, detect, or control internal
corrosion within the company's pipeline. Contributing to the accident were
ineffective Federal inspections of the company's internal corrosion control
program that did not identify deficiencies.

On Saturday, August 19, 2000, a 30-inch-diameter natural gas transmission pipeline operated by El Paso Natural Gas Company ruptured adjacent to the Pecos River near Carlsbad, New Mexico. The released gas ignited and burned for 55 minutes. Twelve persons who were camping under a concrete- decked steel bridge that supported the pipeline across the river were killed and their three vehicles destroyed. Two nearby steel suspension bridges for gas pipelines crossing the river were extensively damaged. During the investigation, NTSB investigators found that the rupture was a result of severe internal
	The explosion left an 86 feet long crater.

corrosion that caused a reduction in pipe wall thickness to the point that the
remaining metal could no longer contain the pressure within the pipe. Furthermore, the corrosion was likely caused within the pipeline by the combination of microbes and such contaminants as moisture, chlorides, oxygen, carbon dioxide, and hydrogen sulfide, the report notes.

One of the major issues of this investigation involved the use of cleaning
pigs. A "pig" is a mechanical device that is used to clean the pipeline.
These devices, which may include scrapers or brushes on the pig body,
are inserted in a pipeline, or launched, and traveled downstream with the
gas flow.

In its report, the Board noted that periodic use of cleaning pigs could
remove water and other liquid and solid contaminants that may cause
corrosion in a pipeline. However, because the section of pipeline that
ruptured could not accommodate pigs, cleaning pigs were not run in this
section.

Another related issue the Board emphasized in the report was the partial
clogging of the drip. The "drip" is a stub line that branched off the
bottom of the gas pipeline. Its purpose is to collect liquids and solids
that may have built up in the pipeline during normal transportation of gas
or after pigging operations.

The investigation revealed that as a likely result of the partial clogging
of the drip upstream of the rupture location, some liquids bypassed the
drip and continued through the pipeline to the eventual rupture site. At the
rupture site, a bend in the pipe had created a low point in the pipeline
where liquids and other residue accumulated and caused corrosion.

Consequently, the Board found that because of the configuration of the
piping, including the location of the pig receiver and the design of the
drip, cleaning pigs could not run in the section of pipeline that ruptured
and therefore removal of substances was incomplete. The Board also
concluded that if the accident section of pipeline had been able to
accommodate cleaning pigs, and if cleaning pigs had been used regularly
with the resulting liquids and solids thoroughly removed from the pipeline
after each pig run, the internal corrosion that developed in this section
would likely have been less severe.

The Board stated in the report that before the accident, EPNG did not have
in place an internal corrosion control program that was adequate to identify
or mitigate the internal corrosion that was occurring in its pipelines. Had
EPNG effectively monitored the quality of gas entering the pipeline and the
operating conditions in the pipeline and periodically sampled and analyzed
the liquids and deposits for corrosivity that were removed from the line, it
would likely have detected the potential for significant corrosion to occur
within the pipeline, the Board determined. Overall, the Board found that the
current Federal pipeline safety regulations do not provide adequate
guidance to pipeline operators or enforcement personnel in mitigating
pipeline internal corrosion.

Blast Crater Image - US Office of Pipeline Safety.