GLOUSTER — A team of engineers has concluded that last November’s explosion of a gas line in the Taylor Road area of Morgan County, near the Athens County line, was due to both landslides and a crack in a girth weld of the pipeline.
On Nov. 16, a quiet morning was abruptly interrupted by an explosion and fire that roared hundreds of feet into the air and torched more than 50 acres. Area residents said the gas line explosion sounded as though an airplane had crashed. Some reported feeling the blast as far as 15 miles away from the site. The failed pipeline was constructed in 1963 and was subject to an in-line inspection in June 2011, less than six months before the explosion.
The root cause analysis was conducted by a team of engineers with Dynamic Risk USA, Golder Associates and Tennessee Gas Pipeline Co., which determined the cause of the gas line failure “was displacement produced by a landslide and an inadequate understanding by (Tennessee Gas Pipeline Co.) of the influence of the geotechnical threats on the pipeline in this location.”
The residence of John and Kathy Sayers was only about 50 feet from the Tennessee Gas line. She was home at the time, and survived the destruction of the house. Another nearby home was destroyed and its occupant, Brandi Stover, also escaped without harm. A barn and an unoccupied structure also burned in the explosion. It took nearly four hours for the last of the flames to be extinguished.
A metallurgical analysis concluded a pre-existing crack in a weld, coupled with stresses from soil movement, helped lead to the explosion. A final report was completed in January and submitted to the federal Pipeline and Hazardous Materials Safety Administration. The Messenger requested a copy of the report on Jan. 17 when the report was due, and was told last month that Tennessee Gas Pipeline Co. objected to the release of the root cause analysis report. The federal agency disagreed with the company’s objection, but allowed an injunction to be sought until July 9. Tennessee Gas apparently did not request an injunction and The Messenger was provided a copy of report Friday.
The root cause analysis states the girth weld was considered stable until acted upon by landslides. Still, the report concludes the weld was cracked.
“The crack in the girth weld, as well as the girth weld itself, acted as a stress concentrator and the displacement (strain) of the pipeline occurred through the ongoing progression of the landslide,” the report states. “Even in the absence of a crack in the girth weld, the landslide likely could have resulted in a pipeline failure at a later time if the landslide remained undetected and unmitigated.”
During the study, the team found evidence of fissures in the land that were not evident immediately after the explosion, but could be seen several days afterward, which lent credence to the soil movement theory. The report notes that there is no evidence that geotechnical threats were considered during the design and construction of the pipeline. It also notes that the soil surrounding the pipeline is comprised of clay, which is relatively rigid during landslide movement and causes more strain on a pipeline than if the soil were mostly loose sand. Landslides were found to be present in the area dating back hundreds and even thousands of years, and are currently active.
During the June 2011 in-line test, the girth weld was found to be in a 159-foot section of the highest bending strain. The report found that standards at the time of the pipeline’s construction did not limit carbon equivalents enough for pipeline materials, and that welding workmanship at the time of construction would not meet current standards.
The investigation team made several recommendations for Tennessee Gas Pipeline Co., including continued development of comprehensive geotechnical threat assessments, establishing procedures for assessment of loads and strains acting on pipelines, development of techniques to monitor land movement areas, gas control to improve response time and continued girth weld condition assessments.
Tennessee Gas Pipeline Co. was owned by El Paso Corp., but that company was purchased in May by Kinder Morgan. Richard Wheatley, spokesman for Kinder Morgan, issued a statement Monday that reiterated the findings of the study and said:
“The company continues to work with PHMSA and the Public Utilities Commission of Ohio and with the families impacted by the incident. The root cause analysis report provides recommendations for actions to be taken by Tennessee Gas. Tennessee Gas developed an integrity verification and remediation plan and is working with PHMSA to finalize the plan, while concurrently conducting further assessments in locations that were identified as having high geotechnical interest by our third-party consultants.”
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The full root cause analysis report can be viewed online at www.athensohiotoday.com