NTSB Safety Recommendation Letter P-73-002 through P-73-011

Page 1Official PDF<.- 5. Tlic flow of gas through the failed service linc was not shut off expeditiously, because the ncccssary valvc key was on a service truck niilcs from the scene. Two other local valves to stop the gas flow were inoperable for the same reason. 6. i t is questionable whether the designation by NSP of only one emergency valve for the entire Lake City distribution system complies with the general intent of 4 9 CFR 192.181(a) That regulation, however, does not establisli objective critcria for the number and location of such valves. 7 A prccoiistructioii meeting was not held between the gas company and the contractor nor was one required to be held. Such a meeting, however, might have shown what gas lines were in the work area and might have averted this accident. 8. The Safety and Health regulation contained in 29 CFR 1926.651(a) does not require that a definite determination be made whether any underground facilities exist in the immediate area of construction work. This part of the regu- l a t i o n a p p e a r s unenforceable as presently written. 9. The compression coupling pulled out as a result of the line being hit and displaced by the bulldozer. 10. The Federal pipeline regulations (49 CFR 192) are vague insofar as establishing the condi- tions under which compression-type couplings may be used. The decision of whether to use such couplings, in effect, is left to the individual gas-company design engineer. 11. The Lake City Fire Department, Police Department, and Office of Civil Defense com- bined effectively to extinguish the fire, evacuate the dead and injured, and maintain order in the affected area. V. PROBABLE CAUSE The National Transportation Safety Board determines that the probable cause of the explo- sion and fire in the department store basement was the ignition of an accumulation of natural 15 gas leaking from the unmarked service line which had been struck by tlie bulldozer. Contributing to the accumulation of gas was the failure of the NSP representative to realize t h a t the 15-foot displacement of the pipe meant that another break had occurred elsewhere. Contributing to the migration and permeation of gas from the leak into the department store was the wooden plug which was inserted in the broken pipe end in an effort to stop the flow of gas, but which sealed off the escape route for the gas., Contributing to the amount of gas released was the unavailability of the required valve key, which necessitated a time-consuming excavation and exposure of tlie buried valve before it could be shut off. VI. RECOMMENDATIONS T h e National Transportation Safety Board recommends that: 1. The Office of Pipeline Safety of the De- partment of Transportation: (a) Undertake a study of fail-safe devices which will stop tlie flow of gas from ruptured lines. Based on the results of this study, OPS should consider amending 4 9 CFR 192 to require the installation of such devices at a p p r o p r i a t e locations in gas distribution systems. (Recommendation No. P-7.3-2) ( b ) I J n d e r t a k e a review of 4 9 CFR. 192..367(b) relative to the uncertainty as to the conditions which permit the use of com- pression couplings, and initiate a rulemaking w h i c h will definitely identify conditions which permit or prohibit the use of compres- sion couplings. If necessary, the review should include a study of objective methods of readily identifying conditions which could produce forces or loads which cannot be sus- tained. (Recommendation No. P-73-3) (c) Amend 4 9 CFR, 192.181(a) to include requirements which express clearly the intent PA F - '73- i#

Page 2of OPS conccrning the number and thc loca- tion of emergency valves in high-pressure gas distribution systems and which treat the need for kcys in the hands of local authoritics (R ccomnie nda tion No P-7.3-4) 2. The Department of L.abor rcview itsOccu- pational Safer) and Health Regulation 29 CFR 1926.651(a) to require that a positivc determi- nation bc made as to the location of under- ground facilitics at the proposed excavation site. (Recoinmendation No. P-7.3-5) 3. Thc American Society of Mechanical Engineers Gas Pipins Standards Committee develop guideliiics to be used by distribution pipelinc opcratms i n designating the location of emergency valves to be uscd to assure a minimum timc to shut down a section of main i n an eniergcncv, (Recommendation No. P-73-6) 4. The Northern Statcs Power fompany: (a) Revisc the Gas Operating and Main- tenance Procedures Manual to emphaske more fully and clearly the importance of rapidly shutting down failed pipelines, evacu- ating persons from thc affected arca, checking buildings adjacent to the le& area, and noti- fying police and fuc officials, Attention should be given to the importance of having thc proper valve keys immediately available. (Recommendation No. P-73-7) (b) Designate emergency valves in its distri- bution systems to permit rapid shutdown of failcd scctions without interrupting gas service to an entire community. (Recommendation No. P-73-8) (c) E.mp1iasizc to the maintenance per- sonnel the importance, need, and desirability of supplying pipeline location information and clearly marking existing lines. (R.ecom- mendation No. P-7.3-9) (d) Undertakc to inform the public more fully as to the nature, characteristics, and hazards of natural gas and the steps to be taken when it is encountered. (Recommenda- tion No. P-7.3-10) 5. The Department of Public Works of Lake City, Minn., requite coordination between the contractors and the affected owners and oper- ators of underground facilities in the city as a prerequisite for obtaining a construction permit. (Recommendation No. P-73-11) 1 6 :#