The area where a natural gas pipeline exploded in Lincoln County in August had not been designated by the company operating the pipeline as an area where a release of natural gas could have high consequences for people's safety or for the environment, according to a preliminary report by the National Transportation Safety Board.
The pipeline rupture, which occurred about 35 miles southwest of Lexington near Danville, killed one woman and sent six other people to the hospital.
The NTSB said in its initial report, released Tuesday, that its investigation is ongoing.
"While on scene, investigators collected sections of the pipeline for metallurgical analysis and testing," the report stated. "Future investigative activity will focus on Enbridge's inspection and maintenance of the pipeline, (High Consequence Area) determination and public awareness, metallurgical evaluation of the pipe, and Enbridge's emergency isolation procedures."
The report said "investigators will also review other inspection anomalies, reportable incidents, and the 2003 rupture." The same pipeline exploded in Morehead in 2003, releasing about 167,100 million cubic feet of natural gas, the report states.
According to the NTSB, the area near the Indian Camp mobile home community where the pipeline ruptured Aug. 1 had not been designated a High Consequence Area by Enbridge. High Consequence Areas are areas "where pipeline releases could have greater consequences to health and safety or the environment," the report states.
Aside from the loss of life and injuries caused by the explosion, the resulting fire destroyed five homes and damaged 14 others. It burned about 30 acres of land, including railroad tracks owned and operated by Norfolk Southern Corp.
The explosion released an estimated 66 million cubic feet of natural gas, according to the report, and threw a 33.2-foot section of pipe 481 feet.
Soon after the explosion, the Pipeline and Hazardous Materials Safety Administration issued an order that required Enbridge to reduce the pressure of the pipeline that exploded to no more than 80% of its normal operating pressure until certain terms are met.
The section of steel pipe that ruptured was 30 inches in diameter, had an electric flash-welded seam and was coated in coal tar, the report states.
At the time of the explosion, the pipe was operating at a pressure of 925 pounds per square inch, which is below the maximum 936 psig allowable, according to the report.
The section of pipeline was put into service in 1957, according to the report. Enbridge performed an in-line inspection "to evaluate pipeline material properties" in 2011, and other in-line inspections were done in 2018 and earlier this year "to evaluate pipeline geometry," according to the report.
"Investigators are reviewing and reassessing the in-line inspection data from the area of the rupture," the NTSB said.
One woman who was burned in the explosion said she had tried to report concerns about the line before the rupture occurred, but she wasn't sure she had reached the right company.