NTSB Safety Recommendation Letter P-78-023

Page 1Official PDFP -100 NATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. ISSUED: J u l y 6 , 1978 Forwarded to: Mr. Lowell Elder Chairman American Society of Mechanical Engineers Gas Piping Standards Committee P-78-23 United Engineering Center 345 East 47th S t r e e t New York, New York 10017 -------------______-____________I_______- SAFETY RECOMMENOAT I O N (S) A t 1 p.m., e . s . t . , ' on December 1, 1 9 7 7 , a 12-inch, cast-iron high- pressure gas main owned by t h e Atlanta Gas Light Company w a s ruptured by an 8-inch s t e e l I-beam p i l e , which was driven through the pipe a t a construction s i t e i n downtown Atlanta, Georgia. &/ Within minutes, n a t u r a l gas a t 10-psig pressure migrated through t h e ground, entered sewer l i n e s and e l e c t r i c conduit systems, and spread i n t o nearby buildings. The gas did n o t i g n i t e , but thousands of people were evacuated from nearby o f f i c e buildings. A valve was closed a t 2:45 p.m. to shut off t h e flow of gas to the ruptured main, and t h e area was declared s a f e a t 4 p.m. The 12-inch gate valve t h a t was used t o shut off t h e flow of gas was located 1,000 f e e t from t h e rupture. The gas w a s fed from one d i r e c t i o n and because t h e main was dead-ended, only one valve w a s required t o shut the system. Because t h i s valve was not designated an emergency valve, t h e g a s company did not have to check and service t h e valve annually a s required by Federal regulations f o r emergency valves. The gas company was unaware t h a t t h e valve cover had been paved over with 8 inches of asphalt; i f t h e valve could not have been located or i f the valve had f a i l e d t o s t o p t h e flow of gas t o t h e main, 22 emergency valves would have t o have been closed t o i s o l a t e the rupture area. - - 1/ For more d e t a i l e d information read "Pipeline Accident Report -- Atlanta Gas Light Company, High-pressure Gas Main Rupture, Atlanta, Georgia, December 1, 1977" (NTSB-PAR-78-3). 2360#

Page 2I f AGL had had t o close t h e 22 valves, t h e company would have t o have r e l i g h t e d customer s e r v i c e s t o t h e e n t i r e downtown business section. Additional emergency valves would make a rapid shutdown more f e a s i b l e by s e c t i o n a l i z i n g t h i s a r e a with more emergency valves. Since emergency valves are required t o be inspected annually, the cost of maintenance influences t h e number of valves s e l e c t e d and, i n some e x i s t i n g systems, only a c e r t a i n percentage of e x i s t i n g valves have been designated emergency valves. The Safety Board believes t h a t t h i s i s not i n t h e b e s t i n t e r e s t of public safety. Because t h i s 12-inch valve had not been designated as an emergency valve by AGL and it had not been checked o r serviced within the p a s t year, t h e Safety Board concludes t h a t Federal regulations should provide s p e c i f i c regulations regarding t h e l o c a t i o n of emergency valves. I n its r e p o r t of a Northern States Power Company accident i n Lake City, Minnesota on October 30, 1 9 7 2 , t h e Safety Board recommended t h a t the Office of Pipeline Safety (Operations) of the U. S. Department of Transportation: Amend 49 CFR 192.181(a) t o include requirements which express c l e a r l y t h e i n t e n t of OPS concerning t h e number and the location of emergency valves i n high- pressure gas d i s t r i b u t i o n systems and which t r e a t t h e need f o r keys i n the hands of l o c a l a u t h o r i t i e s . (Recommendation P-73-4) On A p r i l 3, 1978, a letter from OPSO t o t h e Safety Board s t a t e d t h a t because of " ... t h e v a r i e t y of operating conditions and types of systems i n operation throughout t h e nation, we do not f e e l t h a t s p e c i f i c requirements i n t h i s a r e a could be developed t o adequately apply t o a l l operat ions. " The Safety Board, however, still believes t h a t a problem e x i s t s i n t h e lack of regulations o r guidelines f o r t h e l o c a t i o n and number of emergency valves i n high-pressure d i s t r i b u t i o n systems. In t h e interest of public s a f e t y , t h e Safety Board i s r e d i r e c t i n g its recommendation t o t h e American Society of Mechanical Engineers Gas Piping Standards Committee t o provide guidelines f o r emergency valves s o t h a t operators who share the Board's concern with this problem w i l l have some pro- f e s s i o n a l advice. A s a r e s u l t of i t s i n v e s t i g a t i o n of t h i s accident, the National Transportation Safety Board recommends t h a t t h e American Society of Mechanical Engineers Gas Piping Standards Committee:#

Page 3- 3 - Develop and issue guidelines t o pipeline operators concerning t h e number and location of emergency valves i n high-pressure gas d i s t r i b u t i o n systems. (Class 11, P r i o r i t y Action)(P-78-23) K I N G , Chairman, McADAMS, HOGUE, and DRIVER, Members, concurred i n the above recommendation. '- ,By: James B. King Chairman#