NTSB Safety Recommendation Letter P-77-026

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. ISSUED: September 2 7 , 1977 Forwarded to: M r . G. H. Lawrence President American Gas Association 1515 Wilson Boulevard Arlington, V i r g i n i a 22209 ETY P-77-26 IMEN T I O N ( J A t 2:34 p.m., on May 25, 1977, an explosion and f i r e destroyed a building a t 65-67 Arch S t r e e t i n Greenwich, Connecticut. Two adjacent buildings were a l s o destroyed and another building was heavily damaged. Firemen evacuated r e s i d e n t s from a two-block a r e a 30 minutes a f t e r t h e explosion. The r e s u l t i n g f i r e was extinguished a t 5:31 p.m. Ten persons required medical treatment f o r i n j u r i e s caused by t h e accident. Before t h e accident, a Connecticut Natural Gas Corporation crew was i n the a r e a t o i n s t a l l an i n s u l a t i n g tapping sleeve on a 2-inch gas main. The sleeve is used t o e l e c t r i c a l l y i s o l a t e a s e c t i o n of pipe without i n t e r r u p t i o n of service, and is commonly used by the industry. When the gas company crew expossd t h e gas main, they found t h a t the pipe w a s 3 inches i n diameter i n s t e s l of 2 inches. The crew leader radioed t h e dispatch o f f i c e requesting a d d i t i o n a l information from its records. The main atlas d i d not show any d e t a i l of t h e a r e a , however. Even though a 2-inch shutoff valve f o r the l i n e w a s 12 f e e t away, t h e crew was not aware t h a t t h e 3-inch pipe they exposed w a s not t h e gas main i t s e l f b u t a c t u a l l y w a s a sleeve containing t h e 2-inch gas main. The gas company is aware of its incomplete records and has begun a 3- year program t o v e r i f y and update its records. A gas company supervisor went t o t h e s i t e and advised the work crew t o use a 3-inch i n s u l a t i n g tapping sleeve and t o proceed with t h e task. While c u t t i n g through t h e 3-inch sleeve with a d r i l l i n g machine, t h e 2- inch c a r r i e r pipe w a s a l s o cut. This allowed n a t u r a l gas a t 30-psig pressure t o f i l l the annular space between the 3-inch sleeve and t h e 2- inch pipe and t o escape from the unsealed ends of the sleeve, 11 f e e t away. 2171#

Page 2- 2 - The escaping gas was capped by the pavement above and migra through t h e s o i l . It leaked through cracks i n the stone foundation the Arch S t r e e t building, 5% f e e t f r t h e basement where i t w a s i g n i t e d by some undetermined source and exploded. Two supervisors i n the v i c i n i t y respo emergency r a d i o c a l l and began t o shut off valve leak 16 minutes a f t e r the explosion. Therefore, t h e National Transportation Safety Board re the American Gas Association: Advise its member companies of t h e circumstance accident and urge them t o keep accurate r e and t o i n s t r u c t maintenance crews i n the these f a c i l i t i e s before working on them. (Class 11, P r i o Followtlp) (P-77-26) BAILEY, Acting Chairman, McADAMS, HOGUE, i n the above recommendation. By: Kay Bailey Acting Chairman -#