NTSB Safety Recommendation Letter P-91-017

Page 1Official PDFNational Transportation Safety Board Washington, D.C. 20594 Safety Recommendation Date: July 10, 1992 In r e p l y r e f e r to: P-91-17 (Supersedes Safety Recommendation L e t t e r Issued August 6, 1991) M r . William Badger President National Association o f Regulatory U t i l i t y Commissioners 231 E a s t Baltimore Street Baltimore, Maryland 21202-3486 On August 29, 1990, a natural gas explosion and f i r e destroyed two row houses a t 421-423 North F i f t h S t r e e t and damaged two adjacent houses and t h r e e parked cars i n Allentown, Pennsylvania. One erson was k i l l e d , and nine people, i n c l u d i n g two f i r e f i g h t e r s , were injured. P The National Transportation Safety Board's i n v e s t i g a t i o n disclosed t h a t water l e a k i n g from a circumferential crack i n a &inch c a s t - i r o n municipal water main beneath North F i f t h Street's east side had eroded t h e s o i l foundation o f a low pressure (9 inches water column pressure) 4-inch cast- i r o n U G I Corporation (UGI) gas main beneath the west side o f North F i f t h Street. The gas main subsequently cracked c i r c u m f e r , ~ s t i a l l y and n a t u r a l gas f i l l e d t h e void beneath t h e pavement. N a t u r a l gas w e n migrated through the s o i l and i n t o the basement o f 423 North F i f t h Street, where it i g n i t e d , exploded, and burned. Subsequent m e t a l l u r g i c a l examinations revealed t h a t both c a s t - i r o n mains were s i g n i f i c a n t l y weakened by g r a p h i t i c corrosion. The water main was i n s t a l l e d i n the l a t e 1800s dnd the gas main was i n s t a l l e d i n 1903. The Safety Board reviewed the operating and maintenance practices o f both t h e c i t y and UGI and previous natural gas accidents w i t h i n the c i t y . Based on these reviews, t h e Safety Board determined t h a t : o P r i o r t o August 29, 1990, two breaks had occurred on t h e 4-inch c a s t - i r o n main i n t h e 400 block o f North F i f t h Street on January 15, 1981, and January 24, 1988. ' N T S B B r i e f o f A c c i d e n t F i l e N o . DCAPOFPOOl ( a t t a c h e d ) . 5530A#

Page 22 Since 1970, UGI has averaged 1.2 reported incidentsz per year on its cast-iron mains. From 1925 to 1975, 10 persons were killed, 24 persons were injured, and 2 buildings were destroyed as the result of 2 gas explosions in the city of Allentown. Since 1976, 3 persons were killed, 23 persons were injured, 6 buildings were destroyed, and 5 buildings were damaged as a result of 2 gas explosions in the city of A1 1 entown. The Allentown infrastructure contains many miles of small diameter (8 inches and less) cast-iron gas and water mains installed in the late 1800s and early 1900s that have likely been weakened by corrosion. Water from leaking storm, water, and sewage lines has eroded and dissolved the soil supporting the water and gas mains and other structures creating sinkholes and other underground cavities beneath the city streets. Heavy traffic loads, cracked pavement, and soil movement have increased the stress on buried cast-iron mains. The UGI, the city, and other operators of underground facilities that find sinkholes and other underground voids when excavating have individually documented their findings, but a reciprocal system for centrally documenting or exchanging this information does not exist. Although required by Federal Regulations (49 CFR 192.517), the UGI has not routinely submitted failed pipe segments, including cast-iron failures, for laboratory examination to determine the cause for the failure. Although required by Federal regulations (49 CFR 192.513), the UGI has not implemented an adequate surveillance program t o identify pipeline segments, including cast-iron segments, in its gas distribution system that require corrective action to minimize the threats to public safety. -- -- > I n incident means an event that involves a release o f gas from a pi,. 1 ine I n d a death, personal injury requiring hospitalization, or estimated prapetty damage o f $50,000 or more (before July 1, 1 9 8 4 , the property damas amr vas $5,000).#

Page 33 o The UGI has not routinely submitted failed pipe segments, including cast-iron failures, for laboratory examination to determine the cause for the failure. o The UGI has not implemented a systematic program to identify pipeline segments, including cast-iron segments, in its gas distribution system that require corrective action to minimize the threat to public safety. In its investigation the Safety Board found that the UGI's practices regarding cast-iron failures are not unique in the natural gas distribution industry. From previous investigations, the Safety Board has determined that current industry practices on cast-iron pipe replacement do not adequately identify and remove from service those gas mains that threaten public safety. The practices were found inadequate because they do not generally consider previous graphitization, corrosiveness of the soil, bending strength of small diameter pipe, leak histor,y, and potential pipe damage in areas being renovated or subjected to major adjacent excavation operations. The Safety Board found that most gas operators, rather than submitting failed segments of cast-iron pipe for laboratory analysis to determine to what extent graphitization has weakened the pipe, normally do little more than install a leak clamp around the crack and keep the cast-iron main in operation. Some operators determine a pipe's condition merely by having workers scrape the pipe area adjacent to the crack with a knife blade or rasp to see if they can produce carbon shavings, a clear indication of severe graphitization. Some gas operators have implemented policies that called for replacing a cast-iron main within a city block after it has experienced three breaks and replacing cast-iron mains within a street intersection after two breaks. In its 1986 report3 on a natural gas explosion at Derby, Connecticut, that killed 6 people and injured 12 others, the Safety Board addressed the need for effective, programmed replacement of cast-iron gas mains. In that report, the Safety Board acknowledged that it had previously treated the cast-iron pipe failures on a case-by-case basis, making recommendations for corrective action only to the gas operator involved. The Safety Board also found that the number of miles of cast-iron pipe in gas distribution service had decreased over the years while the number of reportable accidents had remained relatively constant, indicating that the number of leaks per mile of cast-iron main was increasing. The Safety Board acknowledged that some large distribution operators had already begun identifying cast-iron systems prone to failure and establishing replacement programs. However, most operators had not, and no guidance existed at that time to assist or encourage them to develop cast-iron replacement practices. The Safety Board concluded that the industry should begin phasing out the cast-iron piping systems, many of which had been in service for more than 100 years. 3f0r more detailed informetion, resd Pipeline Accident Report-- "Northeast Utitities Service Company, Explosion snd fire, Derby, Connecticut, December 6, 1 9 0 5 " (NTSB/PAR-86/02).#

Page 44 In the years since the Safety Board's report, the industry has taken only limited action to encourage the replacement of deteriorated and aging cast-iron gas distribution systems. In 1986, the Gas Research Institute issued its report, "Cast Iron Maintenance Optimization System." lhis report contained a computerized evaluation model to assist operators in estimating the probability of breaks and leaks on individual segments of cast-iron gas mains, on evaluating repair versus replace options, and on identifying repl acement priorities. Additionally, the American Gas Association (AGA) issued in 1990 a technical report, "Attention, Prioritizing, and Pipe Replacement/Renewal Decisions," that is a collection of papers to "provide a good overview of procedures in current use to maximize the benefits received from repair and replacement expenditures in existing gas systems." Those papers address: o Establishing annual maintenance and replacement budgets; o Establishing attention priorities for the sections of main that compromise a distribution system; and o Determining whether a troublesome section should be repaired or repl aced. Also, the Gas Piping Technology Committee recently approved guide1 ines to assist gas operators in developing cast-iron replacement policies, and the AGA will distribute these to each gas operator that has cast-iron piping systems. The Safety Board i s pleased that the gas industry now has an analytical tool and information on current repair/replacement practices, and soon should have guidelines to aid gas operators in establishing cast-iron system replacement policies. However, this research and development has taken five years and no assurance exists that the gas industry operators will implemen in a timely manner effective cast-iron replacement programs to reduce th threat to public safety. Therefore, the National Transportation Safety Board recommends that t National Association of Regulatory Uti1 ities Commissioners: Encourage its member states to require that each gas operator implement a program, based on factors such as age, pipe diameter, operating pressure, soil corrosiveness, existing graphitic damage, leak history, burial depth, and external loading, to identify and replace in a planned, timely manner cast-iron piping systems that may threaten public safety. (Class 11, Priority Action)(P-91-17) Also, the Safety Board issued Safety Recommendations P-91-12 to the Research and Special Programs Administration; P-91-13 through -16 to Corporation; and P-91-18 and -19 to the city of Allentown.#

Page 55 The National Transportation Safety Board i s an independent Federal agency w i t h t h e s t a t u t o r y r e s p o n s i b i l i t y " t o promote t r a n s p o r t a t i o n s a f e t y by conducting independent accident i n v e s t i g a t i o n s and by formulating s a f e t y improvement recommendations" (Pub1 i c Law 93-633). The Safety Board i s v i t a l l y i n t e r e s t e d i n any a c t i o n taken as a r e s u l t o f i t s safety recommendations. Therefore, it would appreciate a response from you regarding a c t i o n taken o r contemplated w i t h respect t o t h e recommendations i n t h i s l e t t e r . Please r e f e r t o Safety Recommendation P-91-17 i n your r e p l y . KOLSTAD, Chairman, COUGHLIN, Vice Chairman, and LAUBER and HART, Members, concurred i n t h i s recommendation. Member HAMMERSCHMIDT d i d n o t p a r t i c i p a t e . COUGHLIN, Acting Chairman, and LAUBER, KOLSTAD, HART, and HAMMERSCHMIDT, Members, concurred i n t h e r e v i s i a n o f t h i s Safety Recommendation L e t t e r By: Susan M. Coughlin Acting Chairman#

Page 61 NATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. 20594 Pipe1 ine Accident Brief No. DCA90FP001 System Type: Distribution 6AUG 't991 Accident Type: Location : Explosion and Fire 421-423 North F i f t h Street Allentown, Pennsylvania Date: Time: Owner/Operator: Property Damage: Injuries: August 29, 1990 0513 local daylight time UGI Corporation (UGI) $300,000 1 Fatal 9 Nonfatal Material Released: Natural Gas Pressure: 0.32 psig. (9 inches water column) Type Failure: Overstress Component Affected : Cast-Iron Main Description o f the Accident A. natural gas explosion and f i r e destroyed two row houses a t 421-423 North Fifth Street and damaged two adjacent houses and three parked cars in Allentown, Pennsylvania. Two of the injured were fire fighters. Three hours before the accident, a police officer advised the Allentown after-hours dispatcher t h a t water was leaking through pavement cracks i n front of 421 North Fifth Street. The officer said t h a t he believed t h a t I r e p a i r s could be deferred u n t i l the next day Minutes a f t e r 5 a.m., a North Fifth Street resident notified the c i t y of a gas odor i n the area of 421 North Fifth Street and a t 5:09 p . m . , police and fire personnel arrived a t the location. Fire fighters and Four minutes l a t e r , the' explosion occurred. police evacuated residents from houses i n the danger zone, and t o eliminate potential gas leaks from piping i n adjacent residences, they entered houses t o close the gas valves a t inside meter sets. When UGI employees arrived a 5:30 a.m., they began searching for leaking gas and discovered t h a t severa gas valves had not been Jurned o f f . They then shut off gas t o t h residences a t the key-operated curb valves and theri a t meters where valve had not previously been closed. The UGI employees then continued thei search f o r the source of the gas leak and discovered a broken cast-iron main beneath the street. Investigation disclosed that water leaking from a cracked 6-inch c a s t , iron municipal water main had eroded the soil foundation beneath a 4-inch cast-iron UGI gas main. l h e gas main subsequently cracked due soil loads from above, releasing natural gas beneath the pavement. The ga#

Page 7:...I _- Notation 5530 2 DCA90FP001 through the soil and into the basement of 423 North Fifth Street, where it was ignited, exploded, and burned. Excavation after the accident revealed that both the 6-inch cast-iron municipal water main and the 4-inch cast-iron UGI gas pipeline had cracked circumferentially. Sections of each of the pipelines were sent to the Safety Board's laboratory for metallurgical analysis. Analysis revealed that both mains contained areas of significant graphitic corrosion that weakened them. The failure of the gas pipe was inevitable even had the water not eroded its soil foundation because one area of the gas pipe wall was fully graphitized. Numerous factors, individually and/or synergistically, have contributed to the integrity reduction and failure of Allentown, Pennsylvania's cast-iron gas and water mains, most of which were installed in the late 1800s and early 1900s. These include: leaks from storm and sewer lines, water migrating or percolating through the soil, karst development, sinkholes, graphitization, shifting and cracking pavement, increased traffic load, and overburden stress. Probable Cause The National Transportation Safety Board determines that the probable cause of the natural gas explosion and subsequent fire, involving the overstress fracture of an undermined and weakened segment of cast-iron gas main, was the failure of the UGI Corporation to adequately monitor the condition of its gas system and to timely replace cast-iron segments weakened by graphitic corrosion. Reconnnendati ons As a result of its investigation, the National Transportation Safety Board made the following recommendations: --to the Research and Special Programs Administration: Require each gas operator to implement a program, based on factors such as age, pipe diameter, operating pressure, soil corrosiveness, existing graphitic damage, leak history, burial depth, and external loading, to identify and replace in a planned, timely manner cast- iron piping systems that may threaten public safety. (Class 11, Priority Action)(P-91-12) --to the UGI Corporation: Provide initial and recurrent training to local government emergency response personnel on how to control natural gas in emergency situations, including how to locate, identify, and operate outside key-operated shutoff valves. (Class 11, Priority Action) (P-91-13)#

Page 8_ . Hotation 5530 3 Implement a comprehensive gas system surveillance program that: (1) identifies the type of data to be collected on gas system failures, gas leakage surveys, changes in corrosion protection levels, and abnormal operating and maintenance conditipns; (2) establishes the type and frequency of analyses to be performed for identifying ootentiallv unsafe conditions: and I31 soecifies the iorrectivd action to be taken. (Cl'ais 11, Priority Action) (P-91-14) Implement a cast-iron pipe replacement program, based on factors such as age, pipe diameter, operating pressure, soil corrosiveness, existing graphitic damage, leak history, burial depth, and external loading, to identify and replace in a planned, timely manner cast- iron piping systems that may threaten public safety. (Class I f , Priority Act ion) (P-91-15) Document the location of underground voids discovered during excavations and coordinate with the City of Allentown to develop systematic procedures for centrally reporting, documenting, and exchanging information on the location o f underground voids. Class 11, Priority Action) (P-91-16) --to the National Association of Regulatory Utility Commissioners: Encourage its member states to require that "each gas operator implement a program, based on factors such as age, pipe diameter, operating pressure, soil corrosiveness, existing graphitic damage, leak history, burial depth, and external loading, to identify and replace in a planned, timely manner cast-iron piping - systems that may threaten public safety. (Class 11, Priority Action) (P-91-17) --to the City of Allentown: I Coordinate with the UGI Corporation to obtain initial and recurrent training for emergency response personnel on control 1 ing natural gas in emergency situations, including how to locate, identify, and operate outside key-operated shutaff valves. (Class 11, Priority Action) (P-91-18) Coordinate with known underground facility operators in the immediate Allentown vicinity to develop systematic procedures for centrally reporting, documenting, and exchanging information on the location o f underground voids discovered through excavations or other means. (Class 11, Priority Action)(P-91-19) DCA90FP001#