NTSB Safety Recommendation Letter P-77-024 through P-77-025

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. ISSUED: September 27, 1977 Forwarded to: Mr. Robert H. W i l l i s President Connecticut Natural Gas Corporation 233 P e a r l Street Hartford, Connecticut 06101 i SAFETY RECOMMENDATION (S) P-77-24 and 25 .I.-- 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 in Greenwich, Connecticut. Two adjacent buildings were a l s o destroyed and another building w a s heavily damaged. Firemen evacuated r e s i d e n t s from a two-block area 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 area 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 t h e industry. When t h e gas company crew exposed the gas main, they found t h a t t h e pipe was 3 inches i.n diameter instead of 2 inches. The crew leader radioed t h e dispatch o f f i c e and requested a d d i t i o n a l information from its records. The main atlas did not show any d e t a i l of the area, 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 w a s n o t aware t h a t the 3-inch pipe they exposed was not the g a s main itself b u t a c t u a l l y was a sleeve containing t h e 2-inch gas main. 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 the 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, the 2- inch c a r r i e r pipe w a s also c u t . 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 the 2- inch pipe and t o escape from the unsealed ends of the sleeve, 11 feet away. 2171#

Page 2The escaping gas w a s capped by the pavement above and migrate through the s o i l . It leaked through cracks i n the stone foundatio t h e Arch S t r e e t building, 5% f e e t from the severed gas main, and e n t e r the basement where it w a s i g n i t e d by some undetermined s Two supervisors i n the v i c i n i t y responded independently r a d i o c a l l and began t o shut off valves on each s i d e of minutes a f t e r the explosion. The gas company i s aware of its incomplete records and 3-year program t o v e r i f y and update its records. Howeve the p o t e n t i a l f o r another accident of t h i s type, we believe t h a t year program is too long f o r a record update. Therefore, t h e National Transportation Safety Board recomme t h e Connecticut Natural Gas Corporation: Expedite the updating of its gas piping records a s soon a s t o eliminate u n c e r t a i n t i e s on f u t u r e system maintenance wor (Class 11, P r i o r i t y Followup) (P-77-24) I n s t r u c t i t s crews t o a s c e r t a i n p o s i t i v e l y by a l l p o s s i b l means the type and size of e x i s t i n g gas l i n e f a c i l i t i e s before working on them. (Class 11, P r i o r i t y Followup)(P- BAILEY, Acting Chairman, McADAMS, HOGUE, and HALEY, Membe By:#