WISCONSIN GAS CO — Gas distribution — incident on 2009-02-01

Gas distribution incident in MILWAUKEE, MILWAUKEE County, WI. Reported cause: 6. Reported consequences: 0 fatalities, 2 injuries, $429,420 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20090034.

Operator ID: 22763.

Reported incident date: 2/1/2009.

Cause detail: TEMPERATURE

Cause detail: ON SUNDAY, FEBRUARY 1, 2009, AT 2:17AM, THE CITY OF MILWAUKEE POLIECE DEPARTMENT (MPD) NOTIFIED WE ENERGIES CUSTOMER CONTACT CENTER THAT THERE WAS A GAS LEAK IN THE AREA OF 2435 N.10TH STREET, IN THE CITY OF MILWAUKEE, WISCONSIN. MPD ALSO SAID THAT THE MILWAUKEE FIRE DEPARTMENT (MFD) WAS IN ROUT. WE WNERGIES CUSTOMER CONTACT CENTER TRANSFERRED THE CALL TO THEIR GAS CENTRAL DISPATCH WHO, AT 2:19AM, DISPATCHED A GAS DISTRIBUTION WORKER TO RESPOND TO THE GRADE 1 LEAK. WE ENERGIES GRADE 1 LEAKS REQUIRE IMMEDIATE RESPONSE. AT 2:23AM, GAS CENTRAL DISPATCH RECEIVED A CALL FROM THE MFD THAT THEY WERE ON THE SCENE AND THAT THERE WAS A STRONG ODOR THROUGHOUT THE BLOCK, NOT A SINGLE LOCATION AS ORIGINALLY THOUGHT. THE DISPATCHER REPLIED THAT A RESPONDER WAS EN ROUTE AND ESTIMATED ARRIVAL TIME WOULD BE APPROXIMATELY 20 MINUTES. AT 2:24AM GAS CENTRAL DISPATCH RECEIVED A CALL FROM THE MPD THAT THEY WERE AT THE SCENE AND CONFIRMED A STRONG ODOR OF NATURAL GAS IN THE AREA. THE CALL WAS ALSO TO CONFIRM THAT WE ENERGIES WAS RESPONDING. AT 2:28AM, THE MFD CALLED GAS CENTRAL DISPATCH THAT THE STRONG GAS ODOR WAS COMING FROM A BREAK IN THE STREET. GAS CENTRAL DISPATCH, PROVIDED WITH THE ADDITIONAL INFORMATION REGARDING THE NATURE OF LEAK, DISPATCHED 3 ADDITIONAL GAS DISTRIBUTION WORKERS AND A SUPERVISOR WITHIN THE NEXT 12 MINUTES TO PROVIDE ADDITIONAL RESOURCES. JUST PRIOR TO 2:45AM, THE FIRST WE ENERGIES RESPONDER ARRIVED AT THE SCENE. AT 2:45AM, HE INFORMED GAS CENTRAL DISPATCH THAT EXCAVATION WOULD BE REQUIRED AND REQUESTED ADDITIONAL HELP, AN EMERGENCY HOTLINE LOCATE, AND TO HAVE BARRICADES WITH FLASHERS BROUGHT TO THE SITE. GAS DISPATCH RESPONDED ACCORDINGLY AND DISPATCHED ANOTHER EMPLOYEE AT 2:50AM. AT 3:03AM, THE SECOND WE ENERGIES RESPONDER ARRIVED ON THE SCENE FOLLOWED BY SUBSEQUENT WORKERS AT 3:18AM, 3:23AM AND 3:25AM. THEY ASSISTED IN THE PROCESS OF PROBING FOR GAS LOCATION AND MIGRATION, DETERMINING WHICH VALVES AND THEIR LOCATION TO SHUT OFF THE GAS SUPPLY TO THE AREA, AND CHECKED FOR THE PRESENCE OF GAS AT BUILDINGS IN THE AREA. THE RESULTS OF PROBES AND GAS-IN-AIR MEASUREMENTS ALONG THE GAS MAIN, LEAD THE INVESTIGATION AWAY FROM LOCATION OF THE INCIDENT. THE 2 INCH PVC GAS MAIN WAS UNDER THE PAVEMENT, INSERTED IN AN ABANDONED 4" CAST IRON AND SURROUNDED BY FROZEN SOIL CONTRIBUTING TO THE DIFFICULTY OF LOCATING AND STOPPING THE LEAK. AT APPROXIMATELY 3:26AM, THE FIRST OF TWO AREA VALVES REQUIRED TO SHUT DOWN THE AREA FROM THE SUPPLY OF GAS WAS CLOSED. WITHING ONE MINUTE OF COMPLETING THE VALVE CLOSURE, THE TWO UNIT RESIDENCE AT 2435-37 N. 10TH STREET, EXPERIENCED AN INTERIOR EXPLOSION AND SUBSEQUENT FIRE. THE EXPLOSION AND SUBSEQUENT FIRE RESULTED IN THE COMPLETE DESTRUCTION OF THE BUILDING. TWO OF THE OCCUPANTS WHO WERE IN THE BUILDING AT THE TIME OF THE EXPLOSION INCURRED INJURIES REQUIRING HOSPITALIZATION. THE EXPLOSION ALSO SEVERLY DAMAGED A SECOND SINGLE FAMILY RESIDENCE ADJACENT TO IT. THAT BUILDING IS CONSIDERED TO BE NOT SALVAGEABLE. THERE WAS ALSO MINRO DAMAGE SUCH AS BROKEN WINDOWS TO SERVERAL OTHER BUILDINGS INTHE IMMEDIATE AREA. AT 3:37AM, THE GAS DISTRIBUTION WORKER, WHO HAD JUST COMPLETED CLOSING THE FIRST VALVE, CALLED GAS CENTRAL DISPATCH TO INFORM THEM OF THE EXPLOSION AND TO REQUEST MFD TO RETURN TO THE SCENE FOR ASSISTANCE. WE ENERGIES PERSONNEL AT THE SITE, WITH THE ASSISTANCE OF THE MPD AND THE RETURN OF THE MFD, ASSISTED THE INJURED AND EVACUATED THE SURROUNDING BUILDINGS. APPROXIMATELY 10 MINUTES AFTER THE EXPLOSION, THE 2ND GAS VALVE WAS CLOSED SHUTTING OFF THE GAS SUPPLY TO THE AREA OF THE INCIDENT. THIS RESULTED IN 41 GAS METERS BEING AFFECTED. INCE THE AREA WAS MADE SAFE, WE ENERGIES CREWS, AIDED BY ADDITIONAL PERSONNEL AND EQUIPMENT DISPATCHED TO THE SITE, CHECKED BUILDINGS AND PROBED FOR ANY RESIDUL POCKETS OF GAS. SEVERAL EXCAVATIONS OF PAVEMENT AND FROZEN SOIL OVER THE MAIN REQUIRED BEFORE THE SOURCE OF THE LEAK WAS LOCATED. APPROXIMATELY ONE FOOT FROM A SERVICE TEE AND APPROX IMATELY 4 INCHES INTO THE INSERTED CAST IRON MAIN, THE 2 INCH DIAMETER PVC GAS MAIN WAS FOUND COMPLETELY SEVERED IN A CIRCUMFERENTIAL MANNER. TWO PHOTOGRAPHS ARE ATTACHED TO THIS REPORT TO SHOW IN-SITU CONDITIONS UPON FINDING THE BREAK. IT SHOULD BE NOTED THAT MUCH OF THE INSERTED CAST IRON PIPE HAD BEEN DESTROYED IN THE PROCESS TO LOCATE THE BREAK. THE FAILED PIPE AND SURROUNDING CAST IRON PIPE WERE PRESERVED FOR FURTHER ANALYSIS. A FORMER INCIDENT REVIEW WAS CONDUCTED ON FEBRUARY 10, 2009. PARTICIPANTS IN THE REVIEW INCLUDED THE FIVE GAS DISTRIBUTION WORKERS AT THE SCENE PRIOR TO AND AT THE TIME OF THE EXPLOSION, GAS CENTRAL DISPATCH DISPATCHERS, AND OTHER WE ENERGIES PERSONNEL WHO ASSISTED AT THE SCENE AFTER THE INCIDENT. THE INCIDENT REVIEW WAS ALSO ATTENDED BY PIPELINE SAFETY ENGINEERS WITH THE WISCONSIN PUBLIC SERVICE COMMISSION WHO HAD ALSO INSPECTED THE SITE THE DAY OF THE EXPLOSION. THE REVIEW RECOUNTED THE ACTIONS TAKEN BY EACH PARTICIPANT AND INCLUDED COMMUNICATIONS CONDUCTED WITH EACH OTHER, THE MFD, MPD, AND ANY PUBLIC ENCOUNTERED, PARTICULARLY RESIDENTS OF THE AREA. A TECHNICAL REVIEW AND ANALYSIS WAS ALSO PERFORMED TO DETERMINE THE CAUSE OF THE FAILED PVC PIPE. PRIOR TO THE FAILURE, WISCONSIN WAS EXPERIENCING ITS COLDEST WINTER IN RECENT HISTORY. THE COLD TEMPERATURES RESULTED IN THE FROST LINES EXTENDING TO UNUSUAL DEPTHS, ESPECIALLY UNDER THE STREETS AND ROADS WHERE THE INSULATING AFFECTS OF SNOW COVER IS REMOVED. FROST WAS ENCOUNTERED AT THE DEPTH OF THE INSERTED PVC GAS MAIN WHICH WAS MEASURED AT 5 FOOT, 8 INCHES FROM THE TOP OF PAVEMENT. THE CAUSE OF THE BREAK IN THE PVC PIPE WAS DETERMINED TO BE THE RESULT OF THE FORCE OF THE FROST ON THE GAS MAIN DOWNWARD AND THE DIFFERENTIAL SUPPORT UPWARD OF THE EXPOSED PVC MAIN AND THE ADJACENT INSERTED MAIN ON EACH SIDE. THE PVC PIPE WAS SUPPORTED AT EACH END OF THE INSERTION WITH A GROUT EXTENDING ABOUT 4 INCHES INTO THE OPEN ENDS. THIS CONDITION CREATED A BEAM EFFECT AND RESULTED IN A SHEAR LOCATION AT THE ENDS OF THE BEAM. THE SHEAR FORCE EXERTED ON THE PIPE CAUSED IT TO FAIL IN A BRITTLE MANNER. WE ENERGIES IS IN THE PROCESS OF PERFORMING ADDITIONAL LEAK SURVEYS BEYOND THOSE REQUIRED IN CFR 49, PART 192 AND WILL CONTINUE TO PERFORM THOSE SURVEYS UNTIL WINTER CONDITIONS HAVE CEASED. IT IS ALSO IN THE PROCESS OF ACCELERATING ITS EXISTING PROGRAM TO ELIMINATE PVC GAS MAINS.

PHMSA trend classification: significant incident, serious incident, not fire-first.

PHMSA standardized cause: NATURAL FORCE DAMAGE — TEMPERATURE.

PHMSA indexed costs: $429,420 reported total cost, $237,030.932 in 1984 dollars, $583,418.093 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.