The approval from the US Department of Transportation’s Pipeline and Hazardous Materials Safety Administration came after Williams inspected around 230m of pipeline at 16 locations throughout April, Mr Stockton said. “These locations were identified by studying internal inspection data collected last summer,” he said. “These locations were excavated, inspected and repaired over a three-week period.” Eleven sections of pipe were cut out and replaced, and two sections were re-coated, Mr Stockton said. The amount of pipe that was replaced totalled 345m, including some sections that were not in need of repair but were removed to tie-in the places that did need to be replaced in the construction. Mr Stockton noted that only two repairs were required under the federal code; the others were done “on our part to provide an additional margin of safety.”
Pressure on the line was gradually increased on 7 May to reach full pressure on 8 May. The B line, the one that exploded, was repaired and brought back to full pressure on 26 December, while the A line was fully restored on 10 November. About 880m of the B line was replaced following the explosion.
The investigation into the failure is understood to have revealed that the over-50-year-old pipe was corroding from the outside, and that the wall thinning had not been fully reported during intelligent tool inspections of the lines.