NTSB Safety Recommendation Letter P-76-083 through P-76-086

Page 1Official PDFFOR RELE,ASE: 6:3O A,M,, E , s . T , , NOVEMBER 12, 1976 ( 2 0 6 ) 426-8781 ISSUED: November 1 7 , 1976 President Wisconsin Natural Gas Company 233 Lake Avenue Racine, Wisconsin 53401 SAFE-I Y RECOMMENDAT I ON ( S ) P-76-63 through P-76-86 - _______ A t 8:53 a.,m., on August 29, 1.976, an explosion and f i r e destroyed a house a t 6 5 2 1 20th Avenue i n K.enosha, Wisconsin. Two persons were k i l l e d , four persons were i n j u r e d , and two adjacent houses were damaged.. The destroyed house was n o t served by n a t u r a l gas. However, n.atura1 gas, which was escapi-ng a t 58 p s i g pressure from a punctured 2-inch p l a s t i c main located 39 f e e t away, had entered the house through a 6-inch sewer l a t e r a l . The gi-ls was i g n i t e d by an unknown source. After t h e accident, t h e National Transportation Safety Boa.rd's i n v e s t i g a t i o n disclosed t h a t t h e gas main h.ad been i n s t a l l e d by boring through t h e bottom o f t h e sewer t i l e ; the gas main w a s perpendicular t o t h e sewer t i l e . - l/ I n July 1975 t h e Wisconsin Natural Gam Company (Wisconsin) employed a contractor t o construct the gas main paral1,el t o the curb on 20th Avenue. The c o n t r a c t o r used a combination o f open trenching and pneumatic boring techniques t o i n s t a l l t h e main. Pneumatic boring was done i n fr0n.t of the house a t 6521 20th Avenue and a t other l o c a t i o n s along t h e a.venue. An experienced Wisconsin employee inspected the construction. The i n s p e c t o r ' s d a i l y log, which w a s turned i n t o h i s supervisor each evening, recorded t h a t a sewer l a t e r a l had been broken a t 6604 20th Avenue during t h e construction. Supervisory personnel reviewed the logs t o determine t h e status of construction and t o i d e n t i f y any unusual circumstances r e l a t e d t o the construction. Con- s t r u c t i o n procedures were n o t changed, however, as a r e s u l t of t h i s recorded break. TJ-Ttie National 'l'ransportation Safety Board w i l l n o t issue a r e p o r t on t h i s accident. 1 9 2 1#

Page 2- 2 - P-76-83 through P-76-86 Shortly a f t e r construction was completed, the r e s i d e n t s a t 6521 20th Avenue experienced some blockage i n t h e i r sewer l a t e r They employed a contractor t o clean out the l a t e r a l . H e i n s e r t e an auger with a c u t t e r head i n t o the l a t e r a l t o clean it. The blockage was not r e c t i f i e d , however, and a t 8:30 a.m., on August 2 9 , 1976, a sewer cleaning company employee a r r i v e d a t t h e house t o clean t h e sewer l a t e r a l again. A t 8:50 a.m. the cleaner i n s e r t e d an auger i n t o the 6-inch sewer l a t e r a l ; the auger struck and ruptured the 2-inch p l a s t i c gas main. When the gas main was excavated a f t e r the accident, i n v e s t i g a t o r s discov t h a t t h e auger from the f i r s t cleaning attempt had a l s o struck the gas main, but had not punctured it a t t h a t t i m e . The day a f t e r the accident Wisconsin excavated four sewer l a t e r a l s near the ruptured gas main. Two of these l a t e r a l s had been damaged during t h e gas maiil construction when the gas main was i n s t a l l e d p a r t i a l l y i n s i d e the sewer l a t e r a l s . Wisconsin i s continuing t o excavate and inspect sewer l a t e r a l s along 20th Avenue. Wisconsin purchased an e l e c t r o n i c transmitting device which, when i n s e r t e d i n t o a sewer l a t e r a l , determines the depth of the l a t e r a l . This device i s planned f o r use a t a11 other locations where boring was performed t o determine i f other sewer l a t e r a l s were damaged Suspect l a t e r a l s w i l l be excavated and repaired i f necessary. Therefore, the National Transportation Safety Board recommends t h a t Wisconsin Natural Gas Company: Complete inspection of those locations along the construction route (Drawing No. F-3386-2) where gas mains and sewer l a t e r a l s may be i n proximity t o one another and c o r r e c t any d e f i c i e n c i e s . (Class I, Urgent Followup) (P-76-83) Examine i t s records t o determine o t h e r locations where gas l i n e s were i n s t a l l e d near e x i s t i n g sewer f a c i l i t i e s (including a review of sewer blockage complaints), then inspect these locations and take c o r r e c t i v e action where necessary. (Class I, Urgent Followup) (P-76-84)#

Page 3- 3 - P-76-83 through P-76-86 Revise its construction standards to require that underground facilities be located accurately before construction and to pro- vide protection for these facilities near boring operations. (Class I, Urgent Followup) (P-76-85) Inform its inspectors and supervisory personnel of the circumstances of this accident, train them to be alert for similar conditions, and advise them of preventive actions. (Class I, Urgent Fo 1 LOWU~) (I? - 7 6 - 86 ) TODD, Chairman, BAILEY, Vice Chairman, McADAMS, HOGUE, and KALEY, Members, concurred in the above recommendations. By: iebster B. Todd, IJr. Chairman THIS RECOWNDATION WILL BE RELEASED TO THE PUBLIC ON THE ISSUE DATE SHOWN ABOVE. NO PUBLIC DISSEMINATION OF THIS DOCUMENT SHOULD BE MADE PRIOR TO THAT DATE.#