BLACK HILLS ENERGY

Incident Narrative

"GAS LEAK WAS CALLED IN TO THIS LOCATION BY CUSTOMER SMELLING GAS OUTSIDE FOR 3 MINUTES ON SEPT 2, 2020. BHE TECHNICIAN RESPONDED PERFORMED OUTSIDE LEAK INVESTIGATION. LZ-30 AND CGI INSTRUMENTS DETECTED UNDERGROUND LEAK AND WAS PINPOINTED UNDER THE CONCRETE OF O STREET. O STREET TRAFFIC WAS CLOSED AND CONCRETE WAS REMOVED TO VENTILATE LEAK. LEAK WAS ON 16 INCH STEEL MAIN AND LATER DETERMINED TO BE A PINHOLE CORROSION LEAK. A 16 INCH SHORT STOP NEEDED TO BE ORDERED AND CONTRACTOR HIRED TO INSTALL STOP IN ORDER TO DO REPAIR. STREET REMAINED CLOSED TO ALLOW VENTING OF PINHOLE LEAK UNTIL 9-12-2020 AS DATE OF REPAIR. TO REPAIR LEAK, AN EXISTING SHORT STOP WAS USED ALONG WITH A NEWLY INSTALLED SHORTSTOP TO ISOLATE THE LEAK AND CUT OUT PIPE SECTION TO REPLACE. THE CORROSION DEPARTMENT INVESTIGATED THIS DETERMINED THAT THE STEEL MAIN WAS POORLY COATED 1931 VINTAGE PIPE AND THE POINT OF CORROSION WAS DIRECTLY UNDER POOR COATING. IT HAD A CORROSION RATE OF 2.8 MPY. CP TEST POINTS CLOSE TO THIS LOCATION HAD SUFFICIENT CP PROTECTION HISTORICALLY, BUT WERE NOT SUFFICIENT IN THE BELL HOLE OF WHERE THE LEAK OCCURRED. BHE INSTALLED 6 ANODES IN THE BELL HOLE OF THE MAIN AT THIS LOCATION TO RAISE CP PROTECTION TO AN ACCEPTABLE LEVEL. CP TEST POINTS REMAIN AT AN ACCEPTABLE LEVEL OF PROTECTION AFTER REPAIR. ON 9-16-2020, IT WAS DETERMINED THAT COSTS OF EQUIPMENT, CONTRACTORS, AND STREET REPAIR EXCEEDED THE $50,000 LEVEL OF REPORTING."