NTSB Safety Recommendation P-91-017

NTSB safety recommendation P-91-017.

THE NTSB RECOMMENDS THAT THE NATIONAL ASSOCIATION OF REGU LATORY UTILITIES 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.

Priority: CLASS II

Overall Status: Closed - Acceptable Alternate Action

Issued Date: 1991-08-06

Adopted Date: 1991-07-23

Overall Date Closed: 1992-12-28

Synopsis: ON 8/29/90, A NATURAL GAS EXPLOSION & FIRE DESTROYED TWO ROW HOUSES AT 421-423 NORTH FIFTH STREET & DAMAGED TWO ADJACENT HOUSES & THREE PARKED CARS IN ALLENTOWN, PA. ONE PERSON WAS KILLED, & NINE PEOPLE, INCLUDING TWO FIREFIGHTERS, WERE INJURED. THE NTSB'S INVESTIGATION DISCLOSED THAT WATER LEAKING FROM A CIRCUMFERENTIAL CRACK IN A 6-INCH CAST-IRON MUNICIPAL WATER MAIN BENEATH NORTH FIFTH STREET'S EAST SIDE HAD ERODED THE SOIL FOUNDATION OF A LOW PRESSURE (9 INCHES WATER COLUMN PRESSURE) 4-INCH CAST-IRON UGI CORPORATION (UGI) GAS MAIN BENEATH THE WEST SIDE OF NORTH FIFTH STREET. THE GAS MAIN SUBSEQUENTLY CRACKED CIRCUMFERENTIALLY AND NATURAL GAS FILLED THE VOID BENEATH THE PAVEMENT. NATURAL GAS THEN MIGRATED THROUGH THE SOIL & INTO THE BASEMENT OF 423 NORTH FIFTH STREET, WHERE IT IGNITED, EXPLODED, & BURNED. SUBSEQUENT METALLURGICAL EXAMINATIONS REVEALED THAT BOTH CAST-IRON MAINS WERE SIGNIFICANTLY WEAKENED BY GRAPHITIC CORROSION. THE WATER MAIN WAS INSTALLED IN THE LATE 1800S & THE GAS MAIN WAS INSTALLED IN 1903.

Probable Cause: Undermined and weakened segment of cast-iron gas main

Ntsbnumber: DCA90FP011

Report Number: PAB-91-01

Addressee Name: National Association of Utility Commissioners

Addressee Status: Closed - Acceptable Alternate Action

Addressee Date Closed: 1992-12-28

Addressee Acronym: NARUC

Addressee Organization Type: A-Associations

Communication Date: 1992-12-28

Communication Type: Official Correspondence

Communication Contents: THE BOARD IS PLEASED TO LEARN, FROM RECENT CONVERSATIONS WITH NARUC STAFF, & AN AUGUST 16, 1991, LETTER FROM MR. PAUL RODGERS TO THE MEMBERS OF THE NARUC'S COMMITTEE ON GAS, THAT THE NARUC HAS INFORMED ITS MEMBERS OF THE CIRCUMSTANCES SURROUNDING THIS ACCIDENT BY PROVIDING A COPY OF THE BOARD'S RECOMMENDATION LETTER. WE UNDERSTAND THAT THIS IS AS MUCH AS YOUR ORGANIZATION CAN DO IN THE WAY OF ENCOURAGEMENT OF MEMBERS TOWARDS THE GOAL OF THE RECOMMENDATION. THEREFORE, RECOMMENDATION P-91-17 HAS BEEN CLASSIFIED "CLOSED--ACCEPTABLE ALTERNATE ACTION."

Addressee Acronym: NARUC

Addressee Organization Type: A-Associations

Communication Date: 1991-08-16

Communication Type: Official Correspondence

Addressee Acronym: NARUC

Addressee Organization Type: A-Associations

Communication Date: 1992-10-30

Communication Type: Official Correspondence