On May 4, 2020, about 4:36 p.m. local time, a 30-inch diameter interstate natural gas transmission pipeline owned and operated by Enbridge Inc. (Enbridge) ruptured about 3 miles east–northeast of Hillsboro, Kentucky, resulting in a fire. [1] The rupture occurred on Line 10 at a hillside location that was previously identified by Enbridge for geotechnical monitoring because of an active landslide.[2]
Line 10 was the northernmost of three parallel pipelines—Lines 10, 15, and 25—along the same right-of-way. At the time of the rupture, Line 10’s operating pressure was about 674 pounds per square inch, gauge.[3] The rupture occurred at a girth weld at an elevation of about 923 feet.[4] There were no fatalities or injuries, and Enbridge estimated the cost of property damage and emergency response at $11.7 million.
- (a) For more detailed information about this investigation, see the public docket and search for number PLD20LR001. Use the CAROL Query to search safety recommendations and investigations. (b) All times in this report are local time unless otherwise noted.
- The rupture occurred on a Texas Eastern Transmission, Limited Partnership, pipeline. Texas Eastern Transmission is an indirect, 100-percent-owned subsidiary of Enbridge Inc.
- The maximum allowable operating pressure of the pipeline was 936 pounds per square inch, gauge.
- A girth weld is used to join two pipes along their circumference. The girth weld that ruptured had been hydrostatically tested before the pipeline’s initial service in 1952 and retested in 1986; a hydrostatic test involves filling the pipeline with water at a predetermined pressure to test the pipeline’s integrity.
We determined that the probable cause of the pipeline rupture was Enbridge Inc.’s analysis of an active landslide that did not fully address uncertainties associated with pipeline defects, landslide movement, and corresponding pipeline response.
