PEOPLES GAS LIGHT & COKE CO

Incident Narrative

"SUMMARY OF EVENT ON SATURDAY, NOVEMBER 9, 2024, AT 1:33 PM LOCAL TIME (CENTRAL STANDARD TIME) A CONTRACTOR PERFORMING WORK FOR PEOPLE'S GAS LIGHT & COKE (PGL) WAS DOING EXCAVATION WORK ADJACENT TO COUNTY ROAD 2700 NORTH AT APPROXIMATE LATITUDE/LONGITUDE 40.266609/-88.432686. WHILE PERFORMING THE EXCAVATION WORK WITH A BACKHOE, AT THE COMPLETION OF A SWIPE, THE OPERATOR HEARD A POP/HISS AND OBSERVED GAS BLOWING INTO THE AIR. THE NATURAL GAS TRANSMISSION LINE BEING EXCAVATED WAS AT APPROXIMATELY 1,750 PSIG. THE CONTRACTOR PERSONNEL CONTACTED PGL EMPLOYEES WORKING IN THE VICINITY. PGL RESPONDED WITH ON SHIFT PERSONNEL AUGMENTED BY OFF WORK EMPLOYEES. THE AREA WAS MADE SAFE AND THE LEAK WAS ISOLATED USING MANUAL TRANSMISSION LINE VALVES. THE AFFECTED PIPELINE WAS ISOLATED AT APPROXIMATELY 3:00 PM AND WAS DEPRESSURIZED TO ATMOSPHERIC PRESSURE AT 3:30 PM. AT 4:50 PM, PGL ESTIMATED THE RELEASE TO EXCEED 3,000,000 STANDARD CUBIC FEET (SCF). PGL NOTIFIED THE NATIONAL RESPONSE CENTER (NRC) AT 5:06 PM AND THE ILLINOIS COMMERCE COMMISSION (ICC) AT 5:29 PM. A FOLLOW UP CALL WAS MADE TO THE NRC ON MONDAY, NOVEMBER 11, 2024 AT 2:43 PM, DURING WHICH PGL REPORTED A CALCULATED RELEASE VOLUME OF 4.953 MMCF. CAUSES THE DIRECT CAUSE OF THE RELEASE WAS DAMAGE CAUSED BY THE BACKHOE SHOVEL CONTACT TO SURROUNDING SOIL AND/OR INSTALLED EQUIPMENT INCLUDING THE FOLLOWING: A 1"" 3,000 PSIG RATED, THREADED W-K-M DYNASEAL QUARTER TURN BALL VALVE INSTALLED AT THE 12 O'CLOCK POSITION ON THE 12"" CARBON STEEL TRANSMISSION PIPELINE. ON ONE END (TOWARD ATMOSPHERE) OF THIS VALVE WAS A 1"" HEX HEAD PLUG AND ON THE OTHER END (LEADING TO THE 12"" PIPELINE), WAS A 1""X3"" SCHEDULE 160 NIPPLE THAT WAS SCREWED INTO A THREAD-O-LET THAT WAS WELDED TO THE PIPELINE. THE ROOT CAUSE WAS AS-BUILT DRAWINGS WERE NOT UPDATED TO REFLECT THE ABOVE EQUIPMENT FOLLOWING INSTALLATION IN MARCH 2024. DRAWINGS WERE NOT UPDATED BECAUSE THE INSTALLATION WAS THOUGHT TO BE TEMPORARY IN NATURE TO SUPPORT FUTURE PURGING OPERATIONS THAT WOULD BE NEEDED FOR PLANNED CONSTRUCTION. BECAUSE DRAWINGS WERE NOT UPDATED, INFORMATION REGARDING INSTALLATION OF THE EQUIPMENT WAS NOT AVAILABLE TO THE PERSONNEL PERFORMING EXCAVATION ACTIVITIES. CONTRIBUTING TO THE EVENT WAS THE BACKHOE OPERATOR PERFORMING EXCAVATION WITHIN THE TOLERANCE ZONE OF 18"" OF THE PIPELINE. THE BACKHOE OPERATOR'S OPERATOR QUALIFICATION WAS REMOVED BECAUSE OF THE INCIDENT AND IS PENDING REMEDIATION AND REQUALIFICATION. AMOUNT OF GAS RELEASED: BASED ON FURTHER CALCULATIONS USING RELIEF VALVE CAPACITY METHODOLOGY, PGL HAS REVISED THE CALCULATED RELEASE VOLUME TO BE 5,163,905 SCF. THIS INCLUDES 4,842,969 SCF PRIOR TO ISOLATION AND 320,936 SCF FOLLOWING ISOLATION. A 1.25"" OPENING WAS USED DURING THE CALCULATION. THIS OPENING PROVIDES A CONSERVATIVE CALCULATION RELATED TO THE 1"" THREADOLET CONNECTION, WHICH WAS FORCIBLY REMOVED BY THE BACKHOE AND/OR ADJACENT SOIL BEING COMPRESSED DURING EXCAVATION. ACTIONS TAKEN 1. ALL WORK ASSOCIATED WITH THE PROJECT WAS SHUTDOWN PENDING PGL INVESTIGATION. 2. DIRECTION PROVIDED TO PGL AND CONTRACT RESOURCES THAT W-K-M DYNASEALVALVES WILL NOT BE BURIED IN THE FUTURE. A PLAN WAS DEVELOPED TO ADDRESS OTHER LOCATIONS WHERE THESE STYLE VALVES HAVE BEEN INSTALLED. (UPDATE: OTHER LOCATIONS WITH VALVES INSTALLED WITH THE SAME CONFIGURATION HAVE BEEN REMOVED). 3. DIRECTED PGL AND CONTRACT RESOURCES THAT ANYTHING BEING INSTALLED ON PGL FACILITIES IS REQUIRED TO BE DOCUMENTED IN THE AS-BUILT DRAWINGS. 4. DIRECTED CONTRACT RESOURCES THAT ONLY HAND DIGGING WILL OCCUR INSIDE OF THE 18 INCH TOLERANCE ZONE. 5. INFORMED CONTRACT RESOURCES THAT ANY HIT THAT RESULTS IN A RELEASE OF GAS THE EXCAVATOR MUST CALL 911 AND JULIE MUST BE NOTIFIED."