More mishaps occurred on natural gas transmission pipelines in 2004 than in the prior year, but the total dollar amount of the damage was lower, according to statistics from the Department of Transportation’s Office of Pipeline Safety (OPS). The reverse was true for distribution gas pipelines, where the number of incidents dipped slightly in 2004, while the dollar amount of the damage more than doubled.

The OPS reported a total of 103 mishaps on gas transmission lines in 2004, causing property damages of more than $34 million. This compared to 98 incidents on transmission pipelines in 2003 with property damages of $47.1 million

Distribution gas lines had a higher incident rate than transmission pipes during the past year, with 145 total incidents causing property damages of an estimated $48.9 million, the OPS said. This contrasted with 146 incidents on distribution lines in 2003 and property damages of $22.3 million.

Gas transmission and distribution line mishaps resulted in about the same number of deaths in 2004, but fewer injuries. The number of casualties from gas transmission incidents remained constant at one in 2004, while the number of injuries fell to three from eight in 2003, the OPS reported. For distribution lines, the fatalities rose to 12 from 11 in 2003, and the tally of injured declined to 34 from 58 last year.

The causes for incidents on gas transmission lines changed in 2004, the OPS noted. By damage amount, the major culprits were earth movement ($10.6 million in damages), heavy rains/floods ($6.2 million), internal and external corrosion ($5.9 million) and car, truck or other vehicles unrelated to excavation activity ($5.4 million), the agency reported.

External and internal corrosion accounted for the biggest percentage (32%) of all incidents on transmission lines in 2004, and was followed by third-party excavation damage at 16.5%.

Based on damage amounts, the leading causes of gas transmission line incidents in 2003 were external and internal corrosion ($23 million), threads stripped/broken pipeline coupling ($5 million), body of pipe ($3.66 million) and third-party excavation ($3.3 million), according to the OPS.

On gas distribution pipes, damage caused by car, truck or other vehicles unrelated to excavation activity accounted for only 6.2% of all accidents in 2004, but it caused the greatest amount of damage — $17.7 million. This compared to zero damages in this category in 2003.

Third-party excavation damage accounted for the biggest percentage (26.9%) of total distribution line mishaps in 2004, resulting in $9.3 million in damages, the OPS said. Based on damage estimates, other key contributors to distribution line incidents this year were outside forces ($4.58 million), fire/explosion ($3.7 million), earth movement ($3.3 million) and other ($3.5 million).

In 2003, the single biggest cause of damage on gas distribution lines was damage inflicted by outside forces, accounting for 66.4% of all mishaps and nearly $16 million of all damages that year, the OPS reported.

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