NTSB Safety Recommendation Letter P-77-018 through P-77-020

Page 1Official PDF... ,.,. .- . I ;,;,', .-'. ; . , t NATIONAL TRANSPORTATIQN SAFETY BOARD WASHINGTON, D.C. ISSUED: August 2 2 , 1977 M r . David Reid C i t y Conmissioner Cherokee Water and Gas Board Cherokee, Alabama SAFETY RECOMMENDAT I ON (S) A t 9 a.m. c.d.t. on July 30, 1977, a lm-order explosion follmed by f i r e destroyed a house i n Cherokee, Alabama. One person in the house suffered third-degree burns, was hospitalized, and died on August 3, 1977. The National !Transportation Safety Board's continuing investiga- tion of the accident indicates that natural gas, leaking from a broken 2-1/4-inch cast-iron gas main, migrated inb the house via a recently backfilled sewer trench and was ignited by a cigarette lighter. The sewer laterals were )?E.ypendicwZar to and below the gas min. Earth settlenwt of the sewer backfill, aided by recent heavy rainfall, caused the failure of the cast-iron nlain, which was m e d by the Cherokee Water and Gas Board (Cheroltee) . Cherokee previously has mprienced cast-iron gas min failures due to earth settlerent over its recently installed sewers; the potential for additional failures may exist where segments of its cast-iron gas mains have been disturbed by sewer construction and have been l e f t un- supported. Federal regulations (49 CFR 192.755) regarding the protection of cast-iron piplines require tl?at when an operator has knowledge that the support for a segnr?nt of a buried cast-iron pipeline is disturbed by earth mvenwt, that segwnt of the pipeline must be protected, as necessary, against damage. As so3n as feasible, appropriate steps must be taken t o provide permanent protection for the disturbed segment f r m damage that might result from external loads. 2166#

Page 2Maitionally, 49 CFR 192.721, Distribution systems; patrolling, S t a t e s : (a) The frequency of patmllirig mairls must be determind by the severity of the conditions which could cause failure or leakage, and the consequent hazards to public safety. @) Mains in places or on structures where anticipated physical r r o v m t or extmnal l c a a could cause failure or leakage must be patrolled at intervals not exceeding 3 mnths. Apparently, Cherokee did not take these protective actions when it f i r s t k c m aware of the earth s e t t l m t problem. Therefore, the National Transportation Safety Board recornids that the Cherokee Water and Gas Board: Require, during the remaindex of its sewer construction program and all future construction program, tlie suppart and protection of its cast-iron gas mins h accordance w i t h Federal regulations and in a manner acceptable t o the Alabama Public Service Comnission. (Class I, Urgent F o l l m p ) (P-77-18) mamine, support, and protect where necessary, in accordanw w i t h Federal regulations and in a m m e x acceptable to the Public %mice Ccannission, those segments of cast-iron gas mins that have been disturbed already by this s e w e r construction project. ( C l a s s I, Urgent Followup) (P-77-19) mediately begin to patrol its gas distribution system as frequently as necessary while the patid exists for gas main failure due to s e t t l m t . (Class I, Urgent F o l l ~ ) (P-77-20) TODD, Chairman, BAILEY, Vice Chairman, McADAMS and HOGUE, Members, concurred in the above recommendations. HAW, Member, d i d not p a r t i c i p a t e .#