The East Operations manager then called the Clendenin Operations team leader and instructed him to send a crew to the Rocky Hollow and Patterson valve stations to close all of the SM-80 system isolation valves downstream of the rupture.
When the pipeline ruptured, two Columbia Gas operations personnel were repairing a leak on a production pipeline about 4.75 miles from the accident location and about 1.75 miles from the nearest downstream valves at the Rocky Hollow valve station. One of the operations personnel stated that they could hear the roar from the releasing gas. The men went to their truck and drove to a location where they could get cell phone connectivity.18 One called the Columbia Gas control center and was told of the accident. They were familiar with the Lanham station and the pipelines in that area, so they drove to the nearest valve station at Rocky Hollow to close the valves and shut off the gas flow to Line SM-80. Columbia Gas estimated that the Rocky Hollow valves were shut by 1:32 p.m., which was confirmed by the SCADA system trends for Line SM-80 and Line SM-86.
After closing the discharge valves at the Lanham compressor station, the mechanics installed pressure gauges on the three lines to determine which pipeline had ruptured. Once all the isolation valves were closed at Rocky Hollow and Patterson Fork, the rupture was isolated from the gas supply. Gas pressure on Line SM-86 Loop stabilized at 575 psig and Line SM-86 stabilized between 475 psig and 500 psig. The pressure on Line SM-80 dropped to about zero psig, finally confirming that the rupture occurred on Line SM-80.
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