NTSB Safety Recommendation Letter P-82-043 through P-82-044

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. / I S S U E D : December 10, 1982 Mr. G. H. Lawrence President American Gas Association 1515 Wilson Boulevard Arlington, Virginia 22209 \ SAFETY RECOMMENDATION ( S ) P-82-43 and -44 ---.____. At I050 a.m., e.d.t., on September 7, 1982, natural gas, blowing at 1 5 psig from the open ends of a 2 1/4-inch cast-iron gas main located in a deep, narrow excavation at the intersection of Cooper and Marshal Streets in Dublin, Georgia, was ignited by an unknown source. Three City of Dublin gas department employees who were working in the excavation were critically burned. The acting superintendent of the gas department, who was standing at the edge of the excavation, helped the injured out of the ditch and was seriously burned in the process. The City of Dublin, population 16,000, owns and operates a gas distribution system serving 3,900 customers in the city and surrounding areas. Six full-time gas department employees operate and maintain the system: an acting superintendent, a foreman, two equipment operators, and two laborers. The Dublin gas department receives its natural gas from the Southern Natural Gas Company at two town border stations. On September 7, 1982, a private contractor working for the city was installing an 18-inch concrete drain pipe under and across Cooper Street at its intersection with Marshal Street. The contractor requested that a section of 6-inch plastic water line and a section of 2 1/4-inch cast-iron gas main under Cooper Street be lowered since the drain pipe was to be installed at the depth a t which these two facilities were currently located. To lower the gas main in this area, the gas department decided to cut out an 11-foot section of the pipe, deepen the excavation 2 feet, and install a 16-foot-long piece of 1 1/4-inch plastic pipe with an adapter at each end as a temporary gas line to pass below the 18-inch concrete drain. The excavation would then be partially filled so that the 18-inch concrete drain could be installed 3 feet above the temporary gas line. A t 8:15 a.m., the gas department's crew unloaded a backhoe at the site and proceeded to expose the gas main. The crew then deepened the excavation an additional 2 feet below the gas main for the installation of the temporary connection. The gas main was then cleaned to prepare it for cutting and removing the 11-foot section of pipe. Gas department trucks were parked in the street intersection and around the excavation site to act as a traffic barrier; however, the area was not cordoned off nor were any warning signs posted. Portable hand-held, dry chemical fire extinguishers were on the trucks but were not readily accessible at the edge of the excavation. No air breathing equipment was on hand nor were any safety belts and ropes readily available for the emergency retrieval of persons from the excavation. 3628#

Page 2-2- When the two workers had finished cleaning the pipe, the acting superinten the foreman asked them if they wanted the gas main isolated by valve closure and then purged so that the main could be cut without being under pressure. The two workers elected to cut the gas main under 15 psigj they had done this several times in the recent past without incident. Valve books showing the location of all the isolation valves in the system were in the trucks but were not used a t this time. A review of the valve books after the accident showed that closing three valves, one within 2 feet of the excavation and the other two one block away from the excavation, would have isolate section and would have cut off service to only one customer. A t 10:45 a.m., using a three-wheeled hand operated pipe cutter, the two completed the first cut on the gas main at the south end of the excavation. The quickly shifted the pipe cutter to the north end of the excavation and cut the pi Gas was escaping under pressure, but the cut section of pipe remained in positio it was in compression. Another worker, standing a t the edge of the excavation, jumped on the cut section and it fell to the bottom of the ditch. Blowing gas, dust, and debris then filled the ditch. The two other workers in the ditch quickly attempted to connect the plastic replacement section to the gas main using pre-positioned clamps at each end of the open gas main. The workers first attached the replacement section to the north end of the gas main and began tightening the bolts on the clamp. A t 10:50 a.m., as t h e workers were positioning the other end of the pipe to the gas main, the gas ignited and fire burned from both ends of the open gas main. The three workers in t h e ditch, their clothes on fire, crawled out of the ditch or were helped out by the acting superintenden The foreman, who was then across the street, ran back to the site and at 1 radioed the city fire department and requested ambulances and assistance. The fire department arrived at 10:54 a.m. and was followed by the police department and ambulance at 10:56 a.m. The four injured workers were taken to the local hospital for examination. Three of the workers were listed in critical condition and were transported by helicopter to a burn treatment center in Augusta, Georgia. The acting superintendent was hospitalized locally in serious condition. Fire continued at the accident site with flames 18 feet high across the entire excavation. The foreman and a former gas department superintendent, who had bee summoned because he was familiar with the gas system and because they n experienced help, arrived with the police and proceeded to close valves to shut off the gas still fueling the fire. The valve located within 2 feet of the north end of the which was one of the three valves which could have been closed to isolate the are initially could not be reached because of the intense heat and flame. The foreman an former superintendent, therefore, closed the second line of six valves locate block area around the accident site. The closure of the six valves affected only se customers; four of the customers used gas only for heating, and their furnaces were for the summer. Although the precise time of closure was not noted, all valves closed within 10 minutes and the fire burned out about 11:30 a.m. Later, relig procedures were initiated and all customer services were restored by 7 p.m; the 2 1/4-inch gas main was isolated within one block and no customers were affe isolation. The Safety Board is concerned that the practice of cutting gas mains un in other than emergency conditions, instead of isolating the work area by and line purge, and cutting when the pressure has dissipated involves undue r Therefore, the National Transportation Safety Board recommends that the Association:#

Page 3-3- Advise member companies of the circumstances of this accident and urge that they review their operating and maintenance procedures and, if necessary, initiate changes to discontinue any practices involving cutting gas mains while under pressure except in the case of an emergency when required for public safety. (Class I, Urgent Action) (P-82-43) Reemphasize the importance of using proper procedures such as the cordoning off of the work area, the placement of warning signs to alert the public, the use of breathing equipment, belts and ropes, and having operable fire extinguishers accessible at the work site when performing maintenance and/or construction work in which escaping gas may pose a safety hazard to the public or to employees. (Class I, Urgent Action) (P-82-44) BURNETT, Chairman, GOLDMAN, Vice Chairman, McADAMS, RURSLEY, and ENGEN, Members, concurred in these recommendations. B u J i m Burnett Chairman#